Dissertations / Theses on the topic 'Milk composition'

Calibration powders were developed using combinations of milk ingredients for the purpose of calibration of infrared milk analyzers. They were shown to be capable of producing calibrations very similar to conventional calibration milks available commercially. A subsequent collaborative study was carried out involving nine laboratories to assess the performance of the preformulated powders in industrial quality control, payment and dairy herd analysis laboratories. The calibration powders were shown to produce consistent calibrations within laboratories and between laboratories and met AOAC specifications in terms of accuracy and repeatability. The reconstituted solutions were shown to be stable for up to 6 h at 40$ sp circ$C and could be stored under refrigerated conditions and used for repeated analyses for up to 21 days without apparent deterioration in calibration performance. It was concluded that the calibration powders perform as well as conventional calibrants, were more consistent overall and suitable for any calibration application. The calibration powders have the stability and performance characteristics to serve as reference standards for monitoring instrument performance and would be a useful tool for accrediting payment and dairy herd analysis laboratories.

The overall aim of this thesis was to determine the feasibility of breeding for improved milk quality and in particular protein fractions, free amino acids (FAA) and milk colour. To breed for a characteristic such as milk quality it must be; (i) economically or socially important (ii) exhibit genetic variation (i.e be heritable), and (iii) be measurable or genetically correlated with a measurable trait. Gold standard data was determined from 715 milk samples. Spectral data used consisted of ~ 95,000 milk samples from seven research herds and ~ 40,000 milk samples (morning and evening milk samples combined) from 69 commercial herds. The greatest correlation coefficients of external validation obtained for protein fractions, FAA and milk colour were 0.74 (total casein), 0.75 (glycine) and 0.72 (yellowness), respectively. Milk protein fractions and FAA change across calendar months of the year, stage of lactation and parity. A peak in the concentration of all casein fractions was evident in the months of August, September and October. The concentration of glutamic acid was greatest during the months of February, March, April and June when adjusted for milk yield. Changes in individual milk protein fractions and FAA across calendar months of the year and across stages of lactation could provide useful input parameters for decision support tools in the management of product portfolios by processors over time. Heritability of the predicted protein fractions and FAA ranged from 0.04 (beta casein) to 0.61 (total lactoglobulin) and from 0.05 (aspartic acid) to 0.58 (serine), respectively. The coefficient of genetic variation of gold standard protein fractions and FAA ranged from 3.01 (alpha lactalbumin) to 22.98 (total lactoglobulin) and from 1.01 (glutamic acid) to 25.65 (serine), respectively. Milk colour traits were low to moderately heritable ranging from 0.29 (lightness) to 0.35 (yellowness), respectively. The coefficient of genetic variation of milk colour ranged from 0.37 (lightness) to 1.72 (greeness), respectively. Results from this thesis clearly show that some protein fractions, some FAA and milk colour are predictable from MIRS and these predictions exhibit genetic variation and thus breeding for improved milk quality is feasible. The outcome of this thesis is primarily that the prediction of these traits by MIRS could benefit the dairy breeding industry worldwide through genetic selection of animals with higher quality milk and allowing for the more accurate selection of milk for human consumption, infant milk formula, and cheese production. The generated predictions could also be useful for herd and processor management strategies.
L’obiettivo generale della presente tesi è stato quello di determinare la possibilità di poter migliorare, tramite programmi di selezione genetica, la qualità del latte e in particolare le frazioni proteiche, gli amino acidi liberi (FAA) e il colore. Per essere migliorato geneticamente un carattere (incluso la qualità del latte) deve: i) essere di importanza, sia essa economica o anche sociale; ii) esibire variabilità genetica, ossia deve essere ereditabile; iii) essere misurabile o correlato geneticamente con un carattere che sia misurabile. Le analisi di riferimento per i suddetti parametri di qualità del latte sono state determinate su 715 campioni di latte. Il dataset di spettri includeva misurazioni infrarosse su circa 95 000 campioni di latte raccolti in sette aziende sperimentali, mentre altri circa 40 000 spettri (determinati su campioni di latte di entrambe le mungiture giornaliere) erano provenienti da 69 aziende commerciali. I più alti coefficienti di correlazione, in validazione esterna, ottenuti per frazioni proteiche, FAA e colore del latte sono stati rispettivamente di 0.74 (caseine totali), 0.74 (glicina) e 0.72 (indice del giallo). Le frazioni proteiche del latte e gli FFA hanno dimostrato variazioni tra mesi dell’anno, tra stadi di lattazione e tra ordini di parto. Un picco nella concentrazione di tutte le frazioni caseiniche è stato evidente nei mesi di Agosto, Settembre ed Ottobre. La concentrazione di acido glutammico è stata maggiore nei mesi di Febbraio, Marzo, Aprile e Giugno a parità di produzione di latte giornaliera. Le variazioni di frazioni proteiche e FAA attraverso mesi dell’anno e stadi di lattazione possono fornire all’industria di trasformazione lattiero-casearia uno strumento per gestire il proprio portafoglio prodotti lungo uno specifico periodo produttivo. I valori di ereditabilità dei fenotipi predetti hanno avuto un minimo di 0.04 (beta caseina) ed un massimo di 0.61 (lattoglobulina totale) per le frazioni proteiche, mentre per quanto riguarda gli FAA hanno variato tra 0.05 (acido aspartico) e 0.58 (serina). Il coefficiente di variazione genetico per frazioni proteiche misurate ha variato tra 3.01% (alfa lattoalbumina) e 22.98% (lattoglobulina totale), mentre per gli FFA misurati ha variato tra 1.01% (acido glutammico) e 25.65% (serina). Il caratteri di colore del latte hanno dimostrato una ereditabilità medio-bassa, con un range compreso tra 0.29 (luminosità) e 0.35 (indice del giallo). Il coefficiente di variazione genetico del colore del latte ha avuto un minimo di 0.37% (luminosità) ad un massimo di 6.68% (indice del giallo). I risultati della presente tesi dimostrano chiaramente che alcune frazioni proteiche, alcuni FAA e il colore del latte sono di possibile predizione attraverso la tecnologia nel medio-infrarosso, e tali fenotipi predetti hanno variabilità genetica il che implica che programmi di selezione per migliorare la qualità del latte sono possibili. I risultati principali di questa tesi sono che le predizioni di questi caratteri usando la spettroscopia nel medio infrarosso possono rappresentare un beneficio per gli allevatori di vacche da latte attraverso la selezione genetica di animali con una migliore qualità del latte. Inoltre, questa tesi offre delle opportunità per una selezione più accurata del latte destinato al consumo umano, alla produzione di latte per neonati e alla produzione di formaggio. Inoltre, tali predizioni possono rappresentare dlle opportunità per il management aziendale e industriale.

Mastitis is the most common and economically the most important disease of dairy cattle throughout the world. However in Australia, there is an absence of scientifically based data using herd bulk milk supplies. Animals from each of two farms were divided into three groups based on milk sec and NAGase contents. Milk collected from these animals over a two year period was used to study the influence of sec (as a measure of mastitic infection) on milk composition and milk product quality. Milk compositional studies indicated that log sec was positively correlated to the NCN, BSA, chloride, sodium, NAGase (P<0.005), K-casein, {-casein (P<0.01) and IgG (P<0.05) contents, the pH level (P<0.005) and the NCN:total nitrogen, chloride:lactose and sodium:potassium ratios (P<0.005). Log sec was negatively correlated to the SNF, lactose (P<0.005), ft-casein, ~-lactalbumin, ~-lactoglobulin, soluble calcium (P<0.01), total solids, casein and total calcium (P<0.005) contents and the casein:total protein ratio (P<0.005). When milk samples were grouped into sec categories, results indicated that samples with an sec of greater than 500 000 cells/ml were compositionally inferior to samples with an sec of less than 500 000 cells/ml. Pasteurised milk studies indicated that the organoleptic quality of samples with an sec of less than 1 000 000 cells/ml was generally superior to the organoleptic quality of samples with an sec greater than 1 000 000 cells/ml. Skim milk yoghurt studies indicated that the organoleptic quality of both unsweetened and sweetened yoghurts manufactured from milk with an sec of less than 250 000 cells/ml were superior when compared to yoghurtsmanufactured from milk with an sec of greater than 250 000 cells/ml. The rennet coagulating time of milk was significantly longer when the sec became greater than 500 000 cells/ml. Cheddar cheese manufactured from milk with an sec of greater than 500 000 cells/ml had higher moisture and MFFS and lower fat, FDM and pH. Increased losses of fines (P<0.05) into the whey resulted in lower cheese yields (P<0.10). Log sec was negatively correlated to both cheese flavour and body and texture grades (P<0.10) at six months of age. Cheeses became softer, less springy (P<0.10) and cohesive, more adhesive (P<0.05), and less stringy (P<0.05) as the sec of the milk increased. Skim milk powder studies indicated that the effects of elevated sec on skim milk powder properties and organoleptic quality were minimal. From the results obtained in this study it is suggested that sec threshold values of 1 000 000 and 500 000 cells/ml should be used for market milk and manufacture milk supplies respectively.

A total of 596 milk samples with varying fat (3.0 to 4.0%) and protein (3.0 to 4.0%) contents were used to make laboratory-scale cheese and to determine coagulating properties. Higher levels of fat and protein in milk were associated with higher cheese yield. Milk protein has greater effect on cheese yield than milk fat. Adjusted yield increased by 1.91 and 1.29% for every percentage increase in the protein and fat of milk, respectively. Higher levels of fat in milk produced a cheese containing higher fat content and lower protein content. Similarly, higher levels of protein in milk produced higher protein content and lower fat content of cheese. Higher protein to fat ratio (or casein to fat ratio) in milk was associated with better efficiency of fat retention in the cheese. Casein retention in the cheese was not affected by the levels of fat and protein, or protein to fat ratio in milk. Milk adjusted for fat and protein resulted in delayed coagulation and a significant decrease in the curd firmness when compared with unadjusted bulk tank milk having the same levels of the two components.

"Ititu" is a concentrated fermented milk utilized by Borana pastoralists in Southern Ethiopia. The effect of types of container used (glass, fibrous), smoking (smoked, non-smoked) and whey withdrawal (whey, non-whey withdrawn) treatments on the microbiological and chemical compositions of the fermented milks were investigated over a storage period of 28 days. Microbiological results indicated that the type of container used had significant effect (p $>$ 0.05) on total bacterial count (TBC) and lactic acid bacterial counts (LAB) for Weeks 1, 2, 3 and 4 and on coliform count (COLI) for Weeks 3 and 4. These counts determined for the fermented milks in the glass containers were found to be significantly lower compared to those in the fibrous vessels. There was significant difference (p $>$ 0.05) in the overall proximate composition for container and whey withdrawal treatments compared to smoking treatment.
An increased breakdown of the major caseins ($ alpha sb{ rm s1}$ and $ beta$) over the storage period was indicated.
A significant increase was noted on the content of the free amino acids compared to the total amino acids over the storage period.

The zeta potential and size distribution of casein micelles and fat globules from bovine milk have been investigated with the relatively new technique of electroacoustics. This technique requires no dilution or change of environment of the casein micelles or fat globules. The zeta potential obtained at natural pH for casein micelles from a commercial skim milk suspension was —18 mV and the median diameter was 0.2 um A zeta potential of —19 mV was obtained for homogenized fat globules from a commercial milk suspension, a zeta potential of —22 mV was obtained for natural fat globules from a commercial cream suspension and a zeta potential of —36 mV was obtained for fat globules from a recombined milk suspension. The median sizes obtained for the fat globules from the various suspensions were reasonable but at present electroacoustics cannot give a true indication of the spread of the size distribution for the fat globules. Two processes used in the dairy industry were investigated with electroacoustics. The size and zeta potential of casein micelles were monitored during acidification and renneting. For both processes it was found that the trends in zeta potential obtained with electroacoustics during the two processes agreed extremely well with trends reported in the literature. However, the trends in size observed with electroacoustics were different fiom trends reported in the literature. The difi‘erences in the trends in size of the casein micelles obtained during the renneting and acidification processes have been explained in terms of structural changes occurring to the casein micelles during the two processes. Hence the technique of electroacoustics can not only measure zeta potential and apparent particle size but may be able to monitor structural changes in particles during various processes.

Milk expression of recombinant proteins of pharmaceutical value in transgenic dairy animals is an emerging solution for molecules that cannot be made efficiently using the standard bioreactor platform. However, the expression of large quantities of recombinant proteins in the mammary gland can result in phenotypes with compromised lactation physiology. These negative consequences have been vaguely described in the literature and, in most cases; they have not been studied in depth with view to understanding the mechanisms of mammary disruption by transgene expression. Therefore, using a transgenic herd of goats expressing recombinant human butyrylcholinesterase, the main goals of this research were to: a) study the lactation performance and basic milk parameters; b) assess milk composition; c) explore the integrity of epithelial tight junctions, endoplasmic reticulum stress and accelerated cell death; d) investigate delayed lactogenesis; and e) assess the effects of "compensatory treatments" on transgenic lactation performance. Our findings showed that transgenic lactations were characterized by a slow/delayed start of milk production, a relatively normal milk volume at peak and a premature shutdown of milk production compared to controls. These compromised productivities were associated with a disrupted lipid secretion at the level of the secretory epithelium, and a dramatic raise in the presence of phagocytes in milk that was not associated with mammary infection. Milk composition studies indicated that transgenic goats produce lower quantities of caseins and short chain fatty acids. Through determination of serum album presence and Na:K ratio in milk we established the development of permeable tight junctions as an apparent mechanism of lactation disruption in the transgenic animals. Delayed expression of α-lactalbumin was proposed as a major determinant of the delayed lactogenesis observed in the tra
L'expression des protéines recombinantes de valeur pharmaceutique dans la glande mammaire des animaux transgéniques est une solution émergeante pour les molécules qui ne peuvent pas être produites efficacement par les bioréacteurs standards. Toutefois, l'expression de grandes quantités de protéines recombinantes dans la glande mammaire peut entraîner des phénotypes avec une physiologie de la lactation compromise. Ces conséquences négatives ont été vaguement décrites dans la littérature et, dans la plupart des cas ; elles n'ont pas été étudiées en profondeur pour comprendre les mécanismes qui perturbent la glande mammaire suite à l'expression des transgènes. Par conséquent, en utilisant un troupeau de chèvres transgéniques qui expriment la forme recombinée de la butyrylcholinesterase humaine, les principaux objectifs de cette recherche étaient: a) d'étudier la performance de la production laitière et les paramètres de base du lait; b) d'évaluer la composition du lait; c) d'explorer l'intégrité des jonctions serrés épithéliales, le stress du réticulum endoplasmique (RE) et la mort cellulaire accélérée; d) d'enquêter sur la lactogénèse retardée; et e) d'évaluer les effets des "traitements compensatoires" sur la performance de la production laitière des chèvres transgéniques. Nos résultats ont démontré que les lactations transgéniques étaient caractérisées par un départ lent/retardé de la production laitière, un volume de lait relativement normal au pic de la production et un arrêt prématuré de la production laitière par rapport aux contrôles. Ces productivités compromises étaient associées à une perturbation de la sécrétion des lipides au niveau de l'épithélium sécrétoire et une augmentation dramatique des phagocytes dans le lait qui n'était pas associée à une infection mammaire. Les études sur la composition du lait ont indiqués

This dissertation provides a comprehensive and systematic examination of anthropoid primate milk composition and its relationship to a species' evolutionary history, ecological context, and life history strategy. Milk samples from 14 species of anthropoid primate (Alouatta paliatta, Callithrix jacchus, Cebus apella, Gorilla beringei beringei, Gorilla gorilla gorilla, Hylobates lar, Leontopithecus rosalia, Macaca mulatta, Macaca sinica, Pan paniscus, Pan troglodytes, Pongo pygmaeus, Saimiri boliviensis boliviensis, and Symphalangus syndactylus) were analyzed for proximate composition (fat, protein, lactose, dry matter, and minerals) and milk fatty acid composition. The objectives of this study were identification of primitive features in anthropoid milks, shared-derived features of anthropoid families or superfamilies, and unique-derived features of species, including Homo sapiens.Results did not support the null hypothesis of a generalized anthropoid milk composition. Variation among anthropoids in milk fatty acid profiles and proximate milk composition was influenced by phylogeny and the life history strategy of the species, as well as the diet and environment (captive or wild living) of the mother.Maternal diet had a direct influence on fatty acid profiles and created distinct groupings of wild and captive living individuals. Phylogenetic patterns were identified within captive and wild groups, particularly a distinction between milk fatty acid profiles of hominoids (including humans) and monkeys.Significant variation in proximate milk composition was identified at the level of the superfamily. Cercopithecoid milk was highest in mean fat, dry matter, the proportion of energy from fat, and total gross energy. Ceboid milk was highest in mean protein and the proportion of energy from protein. Hominoid milks were lowest in mean fat, protein, dry matter, the proportion of energy from fat, and total gross energy.Hominoid milk also was lowest in the degree of plasticity in milk composition. Milk of captive living monkeys was higher than milk of wild living monkeys in mean fat, percent energy from fat, and total gross energy. Milk fat and energy also were highly variable within captive living monkeys. In contrast, fat and total gross energy were not significantly different between captive and wild living hominoids and were less variabile among captive living hominoids as compared to monkeys. The lack of variability and the relatively low energy values in hominoid milk suggest that it may be buffered against environmental fluctations. Larger body size and a longer duration of lactation may permit hominoids, including humans, to decouple maternal condition from milk energy and instead relying on energy storage.

Milk coagulation properties (MCP) are a fundamental aspect in cheese production, but un unfavorable trend over year on MCP have been observed in several countries. The cheese yield has decreased, accentuating the necessity to provide dairies with milk well suited for dairy products manufacture. During the past decades the focus of milk production has been kg’s of milk protein, but total milk protein content is a poor indicator of MCP, and the lack of an appropriate high-throughput analysis for routine determination of milk coagulation is currently limiting the opportunity to improve MCP by direct selection. Milk protein composition has long been a subject of interest for worldwide dairy researchers. As a consequence, information on milk protein genotype could be utilized to improve milk protein composition and MCP trough marker assisted selection without having to phenotype large progeny groups. Considering such options, it would be desirable to gain further knowledge about effects of milk protein genetic variants on milk protein composition and on MCP. Aims of the study were to investigate the effects of CSN2-CSN3 haplotypes (β-κ-casein) and BLG (β-Lactoglobulin, β-LG) genotypes on milk production traits, contents of protein fractions and detailed protein composition; to investigate the effects of CSN2-CSN3 haplotypes, BLG genotypes, contents of milk protein fractions and protein composition on MCP; to investigate the effect exerted by the relative ratio of κ-CN A to κ-CN B content on MCP and industrial cheese yield of three Italian cheese varieties. The final aim was to estimate genetic parameters of major milk protein fractions and estimate genetic and phenotypic correlation between milk protein fractions and MCP. A new reversed-HPLC method for the separation and quantification of the most common genetic variants of bovine milk proteins was developed and validated testing linearity, repeatability, reproducibility and accuracy. Contents of major protein fractions were measured by this new method in individual milk samples of 2,167 Simmental cows. Protein composition was measured as weight percentage of each casein (CN) fraction to total casein (TCN) and as weight percentage of β-LG to total whey protein (WH). Genotypes at CSN2, CSN3 and BLG loci were also assessed by HPLC and CSN2-CSN3 haplotype probabilities were estimated for each cow. Rennet coagulation time (RCT) and curd firmness (a30) were measured using a computerized renneting meter. Effects of haplotypes and BLG genotypes on yields were weak or trivial. Haplotypes carrying CSN2 B and CSN3 B exhibited greater TCN and casein number (CI), in comparison with all other haplotypes. Genotype BB at BLG was associated with increased protein, TCN and CI, when compared to genotype AA. Haplotypes including CSN3 B were associated with greater κ-CN content and percentage. Allele CSN2 B was associated with an increase of β-CN content, which occurred at the expense of content of αS1-CN. Haplotypes including allele CSN2 A1 exhibited decreased β-, αS2- and γ-CN concentrations and increased αS1- and κ-CN contents, whereas CSN2 I exerted positive effects on β-CN concentration, without altering other protein fractions content. Effects exerted by haplotypes on CN composition were similar to those exhibited on CN fractions contents. Allele BLG A increased β-LG concentration and altered the β-LG to α-Lactalbumin (α-LA) ratio. When protein fractions contents or protein composition were not included in the statistical model, haplotypes carrying CSN3 B allele exhibited shorter RCT and greater a30, in comparison with those carrying CSN3 A, and haplotypes carrying CSN2 B allele were responsible for a noticeable decrease of RCT and for an increase of a30, when compared to haplotype A2A. When effects of protein fractions contents or of protein composition were added to the model, no difference across haplotypes due to CSN3 and CSN2 alleles was observed for MCP, with the exception of the effect of CSN2 B on RCT, which remained markedly favorable. Also, the favorable effect exerted by CSN2 B on a30 was mediated by the increase of β-CN B in milk. Conversely, β-CN B is likely to exert a molecular effect on RCT, which does not depend upon variation of β-CN content associated to allele B. To test if the lack of effect of κ-CN genetic variant would have been observed also on cheese yield, milks with different κ-CN A to κ-CN B content ratios were separately manufactured to produce Montasio, Asiago and Caciotta cheese. Milk was characterized by having similar composition in terms of protein, TCN, CI, CN composition, β-CN composition and pH. Milk with the higher proportion of κ-CN B (HIGHB) exhibited similar coagulation properties but a higher cheese yield in all the investigated cheese in comparison with milk with a lower proportion of κ-CN B (LOWB). However, the increment of yield observed for HIGHB milk in Montasio cheese was ascribed to a greater fat content of HIGHB milk in comparison with LOWB milk. The probability of HIGHB milk giving a cheese yield 5 % greater than that of LOWB milk ranged from 51 to 67 % for Montasio cheese, but was lower than 21 % for Asiago and Caciotta cheeses. Thus, the ratio of κ-CN A to κ-CN B content did not relevantly affect industrial cheese yield when milks of similar CN composition were processed, and an indirect effect due to the higher κ-CN content of κ-CN B milk on cheese yield is to be suggested. Values of heritability for αS1-CN%, κ-CN% and β-CN% were similar and ranging from 0.61 to 0.70, whereas heritability of αS2-CN%, γ-CN% and β-LG% were 0.28, 0.29 and 0.33, respectively. When CSN2-CSN3 haplotype and BLG genotype were accounted for by the model, heritability estimates of all the protein fractions became similar suggesting that proteins synthesis is regulated by specific genes which control the overall production of milk protein. Genetic correlations among the contents of the five CN fractions and between CN fractions and WH fractions were generally low. Generally, all the CN fractions were also moderately positively correlated with WH. When data where adjusted for CSN2-CSN3 haplotype and BLG genotype, genetic correlations among the contents of protein fractions markedly increased confirming that all the fractions undergone a common regulation. The content and the relative proportion of κ-CN were not genetically correlated with RCT, αS1- and αS2-CN were unfavourately correlated with RCT, but increasing the content of β-CN in milk would result in a shorter RCT. Stronger curds were associated with higher κ-CN and β-CN, and with lower αS1-, αS2-, and γ-CN contents and proportions. Results confirm the lack of favorable associations between TCN and MCP indicating that other traits, i.e. milk protein fractions, should be used for the genetic improvement of cheese-making properties.
Le proprietà di coagulazione del latte (MCP) sono un aspetto fondamentale nella produzione di formaggio, tuttavia, negli ultimi anni, è stato registrato un andamento sfavorevole della coagulazione del latte in diversi Paesi. La resa in formaggio è diminuita, accentuando la necessità di fornire i caseifici con latte più adatto per la trasformazione in formaggio. Nel corso degli ultimi decenni il miglioramento genetico si è focalizzato sui kg di proteina del latte, ma il contenuto totale di proteina non sembra essere un buon indicatore delle MCP, e la mancanza di un metodo di analisi che consenta la determinazione delle MCP su larga scala attualmente limita la possibilità di migliorare le MCP attraverso una selezione diretta. La composizione proteica del latte è stato a lungo oggetto di interesse per i ricercatori di tutto il mondo. Di conseguenza, le informazioni sul genotipo delle proteine del latte potrebbero essere utilizzate per migliorare la composizione della proteina oppure nella selezione assistita da marcatori per migliorare le MCP, senza dover fenotipizzare grandi gruppi di progenie. Alla luce di tali possibilità, sarebbe auspicabile poter acquisire ulteriori conoscenze sugli effetti delle varianti genetiche delle proteine sulla composizione proteica del latte e sulle MCP. Obiettivi di questa tesi sono stati: studiare gli effetti dell’aplotipo CSN2-CSN3 (β-κ-caseina) e del genotipo al locus BLG (β-lattoglobulina, β-LG) su caratteri produttivi, contenuto di frazioni proteiche e composizione proteica; studiare gli effetti dell’aplotipo CSN2-CSN3 e del genotipo al locus BLG, del contenuto di frazioni proteiche e della composizione proteica sulle MCP, studiare l'effetto esercitato dal rapporto relativo tra κ-CN A e B sulle MCP e sulla resa industriale in tre varietà di formaggi italiani. Inoltre, ultimo obiettivo del lavoro è stato la stima dei parametri genetici delle principali frazioni proteiche del latte e delle correlazioni genetiche e fenotipiche tra le frazioni proteiche e le MCP. Un nuovo metodo di analisi HPLC a fase inversa per la separazione e la quantificazione delle più comuni varianti genetiche delle proteine del latte bovino è stato sviluppato e validato attraverso test di linearità, ripetibilità, riproducibilità e accuratezza. Il contenuto delle principali frazioni proteiche è stato misurato con questo nuovo metodo in campioni di latte individuale di 2,167 bovine di razza Simmental. La composizione proteica è stata espressa come percentuale in peso di ogni frazione caseinica rispetto al contenuto totale di caseina (TCN) e come percentuale del peso della β-LG sul totale di proteine del siero (WH). Il genotipo ai loci CSN2, CSN3 e BLG è stato determinato tramite HPLC e le probabilità aplotipiche per gli aplotipi CSN2-CSN3 sono state stimate per ogni animale. Tempo di coagulazione (RCT) e consistenza del coagulo (a30) sono stati misurati utilizzando un lattodinamografo. Gli effetti dell’aplotipo delle caseine e del genotipo al locus BLG sui caratteri produttivi sono stati limitati o trascurabili. Gli aplotipi contenenti gli alleli CSN2 B e CSN3 B hanno mostrato valori più elevati di TCN e un indice caseinico (CI) superiore, rispetto a tutti gli altri aplotipi. Il genotipo BB al locus BLG è stato associato ad un aumento del contenuto proteico e ad un CI superiore rispetto al genotipo AA. Gli aplotipi contenenti l’allele CSN3 B sono stati associati a contenuti e percentuali di κ-CN maggiori. L’allele CSN2 B è risultato associato con un aumento del contenuto di β-CN, che si è verificato a scapito del contenuto di αS1-CN. Gli aplotipi che includevano la variante CSN2 A1 hanno mostrato una diminuzione del contenuto di β-, αS2- e γ-CN e un aumento del contenuto di αS1- e κ-CN, mentre la variante CSN2 I ha esercitato effetti positivi sulla concentrazione di β-CN, senza alterare il contenuto delle altre frazioni proteiche. L’allele A al locus BLG è stato associato ad una maggiore concentrazione di β-LG e ad un più elevato rapporto tra β-LG e α-lattoalbumina (α-LA). Quando il contenuto delle frazioni proteiche o la composizione della proteina non erano inclusi nel modello statistico, gli aplotipi contenenti l’allele CSN3 B erano associati ad RCT più brevi ed a30 maggiori, rispetto a quelli che includevano l’allele CSN3 A, e gli aplotipi contenenti la variante CSN2 B erano responsabili di una notevole diminuzione dei valori di RCT e per valori di a30 maggiori, rispetto agli aplotipi contenente la variante A2. Quando gli effetti del contenuto delle frazioni proteiche o della composizione proteica sono stati inclusi nel modello statistico, nessuna differenza tra aplotipi riconducibile agli alleli ai loci CSN3 e CSN2 è stata osservata per le MCP, con l'eccezione dell’effetto della CSN2 B su RCT, che è rimasto molto favorevole. L'effetto favorevole esercitato dall’allele CSN2 B su a30 è risultato mediato dall’aumento di β-CN B nel latte. Al contrario, la β-CN B esercita probabilmente un effetto diretto su RCT, che non dipende dalla variazione del contenuto di β-CN associato all’allele B. Per verificare se la mancanza di effetto diretto delle varianti genetiche di κ-CN sarebbe stato osservato anche sulla resa in formaggio, latte con differenti rapporti tra κ-CN A e B sono stati lavorati separatamente per la produzione di Montasio, Asiago e Caciotta. Il latte lavorato aveva composizione simile in termini di proteina, TCN, CI, composizione caseinica, composizione della β-CN e pH simile. Il latte con la percentuale maggiore di κ-CN B (HIGHB) ha presentato valori di MCP simili, ma una resa superiore in tutti i tipi di formaggio esaminati, rispetto al latte con una percentuale inferiore di κ-CN B (LOWB). Tuttavia, l'incremento di resa osservato per il formaggio Montasio è stato attribuito a un maggior contenuto di grasso del latte HIGHB in confronto con il latte LOWB. La probabilità del latte HIGHB di dare un formaggio con una resa del 5% superiore a quella del latte LOWB variava dal 51 al 67% per il Montasio, ma è stata inferiore al 21% per Asiago e Caciotta. Il rapporto tra le varianti A e B di κ-CN non ha quindi influito in modo rilevante sulla resa casearia industriale, quando la composizione del latte era bilanciata per la composizione caseinica, ed è possibile supporre pertanto che vi sia un effetto indiretto delle varianti di κ-CN sulla resa casearia, a causa del più elevato contenuto di κ-CN associato alla variante B. I valori di ereditabilità per αS1-CN%, κ-CN% e β-CN% erano simili e variabili da 0.61 al 0.70, mentre l’ereditabilità di αS2-CN%, γ-CN% e β-LG% erano 0.28, 0.29 e 0.33, rispettivamente. Quando l’effetto dell’aplotipo CSN2-CSN3 e del genotipo al locus BLG sono stati inclusi nel modello, le stime di ereditabilità di tutte le frazioni proteiche sono divenute simili suggerendo che la sintesi di proteine del latte sia sottoposta a un controllo genetico da parte di geni specifici che controllano il livello generale di proteina del latte. Le correlazioni genetiche tra il contenuto delle 5 frazioni caseiniche e tra le frazioni caseiniche e le frazioni sieriche erano generalmente basse. In generale, tutte le frazioni caseiniche erano anche moderatamente positivamente correlata con WH, suggerendo che vi sia una regolazione generale del livello di proteina del latte che coinvolge contemporaneamente TCN e WH. Quando l’effetto dell’aplotipo CSN2-CSN3 e del genotipo al locus BLG sono stati inclusi nel modello, le correlazioni genetiche tra i contenuti delle frazione proteiche sono aumentate significativamente, supportando l’ipotesi che tutte le frazioni siano oggetto di una regolazione generale. Il contenuto di κ-CN del latte non è risultato essere geneticamente correlato con RCT, αS1- and αS2-CN hanno mostrato una correlazione sfavorevole con RCT, mentre un aumento della β-CN nel latte sarebbe a favore di RCT più brevi. Coaguli più consistenti sono stati associati ad un maggior contenuto di κ-CN e β-CN e ad un minor contenuto di αS1-, αS2-, e γ-CN. I risultati ottenuti confermano la mancanza di un’associazione favorevole tra TCN e MCP, sottolineando l’esigenza di utilizzare altri caratteri, come il contenuto delle frazioni proteiche, per il miglioramento genetico delle proprietà casearie del latte.

In conditions where supplementation of poor quality diets is a major challenge, forage legumes such as Sericea lespedeza can be a good alternative supplement for protein at lower cost than most commercial concentrates. From studies done on Sericea lespedeza it is found plausible and valuable to supplement urea with Sericea lespedeza to strategically combat the deleterious effect of condensed tannins in the Sericea lespedeza and provide nitrogen in the rumen. This study was aimed to evaluate the effect of replacing sunflower oilcake with urea (a rumen degradable protein RDP source) or Sericea lespedeza (rumen undegradable protein RUP source) mixed with urea as nitrogen/protein sources on nutrient utilization, milk yield and milk composition of Saanen dairy goats. A digestibility and lactation study were conducted at the University of Pretoria Research Farm and chemical analysis performed at the University Nutrilab. A 30 days digestibility study was conducted on male Saanen goats after the lactation study, with 23 days adaptation and 7 days data collection period. Nine male goats were randomised and allocated to the three treatments in metabolism cages. In the lactation study 36 dairy goats were blocked according to milk collected on first month of lactation into high, medium and low milk yielders, then allocated to the three treatments of total mixed rations containing sunflower oilcake (T1) at 7% main protein source, T2 (urea at 1%) and T3- Sericea lespedeza at 12.5% mixed with urea according to a complete randomised block design (CRBD). Milk samples were collected from individual goats monthly at two consecutive milking’s. The samples were analysed for milk fat, protein, lactose, somatic cell count and milk urea nitrogen using a Milko-Scan analyser (at Irene Lacto lab). In the digestibility study, dry matter intake was significantly higher for goats fed on Sericea lespedeza with urea (T3) diet than goats fed on T1 and T2 diet. Goats on T3 diet had also significantly higher organic matter and crude protein intake than those goats fed on the other two TMR diets. The results also shows that the mean daily milk yields for the goats in the T1, T2 and T3 were 2.56, 2.46 and 2.52 kg per day respectively. T2 group had higher milk fat % (3.61) and higher milk urea nitrogen (MUN - 25.70 mg N/dl) than the other two treatments. T1 had significantly higher milk protein %. There was a great difference in milk composition of the afternoon milk as compared to the morning milk. The three TMRs had no significant difference in the nitrogen utilization and nitrogen excretion. It is then concluded that Sericea lespedeza mixed with urea can be used as subsititutes for sunflower oilcake in the diets of dairy goats since no negetive effect was found. However further investigations are needed.
Dissertation (MSc Agric)--University of Pretoria, 2017.
DAAD-NRF
International Foundation for Science (IFS)
Animal and Wildlife Sciences
MSc (Agric)
Unrestricted

Thesis (M. Tech. (Biomedical technology)) - Central University of technology, Free State, 2013
Thirty-one years after the discovery and isolation of the human immunodeficiency virus (HIV) by French and American scientists, much progress has been made in basic research, clinical treatment, and public heath prevention. Although, much evidence of mother-to-child-transmission (MTCT) of HIV has been amassed since then, not much of it describes the effects of HIV on the nutrient composition of breast milk. The aim of this study was to determine the effects of HIV on the nutrient composition of breast milk, by studying two groups of adult lactating respondents from the same socio-economic background, who were chosen randomly and participated voluntarily. The study population consisted of 60 breastfeeding mothers, divided into two groups of 30 mothers each. Group one represented the control group of HIV non-infected mothers whereas group two consisted of HIV-infected mothers who did not receive any treatment. After a registered medical nurse took blood and breast milk samples, analysis was done on ethylenediamine tetra-acetic acid (EDTA) whole blood to determine the haematological and immunological parameters and breast milk was analyzed for nutrient composition. Standard laboratory operating procedures (SOP) were followed, throughout, to determine the parameters of the blood and breast milk samples. Results showed that associations between the socio-economic statuses (SES) of the two respondent groups could be established. Albeit differences were not significant, some were, however, detected in the number of people contributing to the household income of the respondents (p = 0.0051), their employment status (p < 0.0001) and the availability of water sources (p = 0.1124). It is believed that factors, such as the prevalence of HIV, if related to the different levels of SES may play an important role in the outcome of the health statuses of individuals at different levels of society. By implication, it is not the different levels of SES, but rather factors related to the different levels of SES that have an impact. Significant differences could be seen in the haematological variables between the two respondent groups: Red blood cell count (RBC) (p < 0.0001), hemoglobin (Hb) levels (p = 0.0119), hematocrit (Hct) (p = 0.0031), mean corpuscular volume (MCV) (p = 0.0005), mean corpuscular hemoglobin (MCH) (p = 0.0043) and monocyte count (p = 0.0275). These differences, however, were not significant to this study. Other differences that were significant were immunological parameters between the two respondent groups: CD4 cell count (p < 0.0001) and viral load, done only on the blood of the HIV-infected respondent group. The CD4 cell count is used as a guideline for the initiation of treatment for HIV-infected persons and is required to accurately assess the immune status of any patient at any given time. The viral load has long been established as a strong predictor of the rate of disease progression. The only significant difference in the breast milk composition was reflected in the following variables between the two groups: percentage (%) proteins (p < 0.0001) and calcium levels (p = 0.0081). The median and mean values of the percentage proteins were elevated in the subject group of mothers living with HIV, while calcium levels in the same group showed a decrease in both median and mean values. The lack of significant differences between the groups might be due to the small study population. If nothing else, this study highlights the need for further trials to evaluate the true effects of HIV on the nutrient composition of breast milk.

Milk proteins have been widely studied in the last fifty years because of their great importance and strong relationship with milk quality and milk coagulation properties (MCP). The general interest in dairy science gave the possibility to achieve many important scientific results, such as polymorphism identification concerning this kind of molecules and differences among species and breeds. Studies which considered effects of milk protein polymorphisms on milk characteristics and milk properties started since 1970 in such countries like Italy, where more than 70% of milk is used in the cheese-making industry and transformed in typical products, which play a key role for the economic valorization, like the Protected Designation of Origin Products. The importance of this kind of topics and the possibility to improve milk and the cheese-making processes brought to a strong change concerning breeding value aims and selection strategies employed in dairy science. In the last decades many farms focused on high milk production animals, but this sort of management took to a worsening of health and functional characteristics of the animals, such as fitness, robustness, longevity and fertility, as well as genetic variability. Today situation get different, because an acceptable compromise was found among farm productivity and milk quality; greater economic value was given to typical products and local breeds were protected, because strong linked to the environmental preservation, local tradition, and historical tradition conservation; moreover crossbreeding schemes are employed, because they carry out very appreciable animal performances, but breed merits are kept and at the same time some very important effect, like heterosis, are exploited. Considering such options and lack of studies in literature, it would be desirable to gain further knowledge on the effects of some sources of variation on milk protein fraction and milk protein component. Aims of the study were to find and develop a new reverse phase HPLC method able to quantify and identify the most common milk protein fractions; to investigate the sources of variation on milk protein fractions and composition of individual milk samples collected in dairy herds which employed crossbreeding schemes; to investigate the sources of variation on milk protein fractions and composition of individual milk samples collected in multi-breed dairy herds located in mountainous areas. A new reverse phase HPLC method for the identification and quantification of the most common protein fractions and genetic variants of bovine milk was developed, including some minor components, like lactoferrin. The method was validated by testing linearity and repeatability. For genetic variants identification, milk of DNA-genotyped animals was used to find peaks and to associate them with the known genotype of animals. Calibrations with a coefficient of determination higher than 0.99 were obtained for every single genetic protein variant, nevertheless commercial standards for every variant were not available. Method was after employed for individual milk samples collected in crossbred dairy herds located in the north of Italy and to compare pure Holstein with different bull semen of Alpine European and Nordic breeds, like Montbeliarde, Brown Swiss and Swedish Red. It came out that milk protein fractions, are influenced by the stage of lactation and parity; breed effect was significant especially for κ-CN, α-LA and β-Lg, which are linked. Among crossbred combinations, Brown Swiss and Montbeliarde crosses showed high significance, because of the selection strategy or the natural presence of the B variant of the κ-CN, respectively; B variant is very important in the cheese making industry because animals carrying AB or BB genotype show a higher milk casein content and also a higher milk quality. Method was after employed for individual milk samples collected in herds where two breeds were attended at least; six breeds were employed, three high-production and three dual-purpose: Holstein-Friesian, Brown Swiss, Jersey and Gray Alpine, Simmental and Rendena, respectively. Four types of dairy herd were considered in this study: modern herd type, traditional herd type with silage use, traditional herd type without grazing use and traditional original herd type. Effect of stage of lactation and parity influenced milk protein fractions; among breeds, Jersey showed a higher milk protein content than the other breeds; in Gray Alpine a new genetic κ-CN variant was detected using our reverse phase HPLC method, but not identified, so further investigation is required to confirm this aspect, employing other techniques maybe coupled with HPLC. Traditional dairy herd type with silage use was the best strategy with the highest milk protein content, although it showed the highest somatic cell content; modern herd type gave unexpectedly inferior performances and traditional herd without grazing was instead the worse concerning milk protein content.
Negli ultimi cinquant’anni le proteine del latte sono state oggetto di ricerca approfondita, date le loro caratteristiche e l’importanza ad esse attribuita per quanto riguarda qualità e capacità di coagulazione del latte. L’interesse creatosi ha reso possibile il raggiungimento di diversi risultati di grande rilevanza scientifica, come l’identificazione di polimorfismi a livello di queste molecole e di differenze anche piuttosto accentuate tra diverse specie e razze bovine. Gli studi che hanno considerato gli effetti dei polimorfismi proteici sulle caratteristiche e proprietà del latte hanno trovato ampio spazio in Italia, già a partire dai primi anni ’70, dove gran parte del latte viene usato nell’industria lattiero-casearia e dove è fondamentale l’ottimizzazione della produzione di prodotti trasformati e prodotti tipici, tra i quali figurano anche i Prodotti a Denominazione di Origine Protetta. In zootecnia la rilevanza di tali argomenti e la possibilità di migliorare considerevolmente il latte e il suo processo di trasformazione hanno portato un profondo cambiamento per quanto riguarda gli obiettivi e le strategie di selezione e miglioramento genetico degli animali da reddito; nel corso degli ultimi anni molte aziende del settore si sono concentrate su animali altamente produttivi in termini di quantità di latte prodotto, ma tale management ha portato purtroppo ad un netto peggioramento della salute e delle caratteristiche funzionali degli animali, quali la fitness, la rusticità, la longevità e la fertilità, oltre alla perdita di preziosa variabilità genetica. Oggi la situazione è diversa, in quanto si è cercato di trovare un compromesso accettabile tra produttività degli allevamenti e qualità di prodotto, investendo economicamente nella valorizzazione di prodotti tipici e tutelando razze meno produttive, ma fondamentali per esempio nel contesto rurale, ampiamente diffuso in Italia, proprio per le loro caratteristiche di adattabilità e rusticità, oltre ad essere utili per la salvaguarda del territorio e della tradizione; oppure utilizzando gli schemi di incrocio tra razze, che riescono a garantire ottime performance degli animali, mantenendo le caratteristiche di razza e contemporaneamente sfruttano alcuni effetti di grande utilità, come l’ eterosi. Alla luce di tali cambiamenti, e data ancora la scarsità di informazioni presente in letteratura, è auspicabile poter continuare ad acquisire preziose informazioni sugli effetti di alcune fonti di variazione sulla componente proteica del latte. Obiettivi della tesi sono stati: sviluppare e validare un nuovo metodo HPLC in fase inversa atto a identificare e quantificare le frazioni proteiche più comuni del latte bovino; studiare gli effetti di alcune fonti di variazioni sulle frazioni proteiche individuate con tale metodica di latte bovino individuale proveniente da allevamenti che si servissero degli schemi di incrocio al loro interno; studiare gli effetti di alcune fonti di variazione sulle frazioni proteiche di latte bovino individuale proveniente da allevamenti montani multi-razza. Un nuovo metodo di analisi HPLC in fase inversa è stato sviluppato e validato per consentire l’identificazione e la contemporanea quantificazione delle più comuni frazioni proteiche, comprese le loro varianti genetiche, presenti nel latte bovino, oltre a componenti minori poco conosciute ma di grande interesse, come la lattoferrina. Tale nuova metodica è stata sottoposta a test di linearità e ripetibilità. Per l’identificazione delle varianti è stato utilizzato latte proveniente da animali precedentemente genotipizzati, in modo da riconoscere i picchi a livello cromatografico ed associarli al corretto genotipo della data proteina presa in esame. E’ risultato possibile ottenere le calibrazioni corrette con un coefficiente di determinazione superiore a 0.99 per tutte le singole varianti genetiche delle frazioni proteiche, sebbene non fossero disponibili standard commerciali per varianti singole. Tale metodo è stato poi applicato per l’analisi di latte individuale proveniente da allevamenti del nord Italia che utilizzavano lo schema di incrocio di prima e seconda generazione tra razza pura Holstein e tre differenti semi di tori del nord Europa e dell’arco Alpino, quali razza Montbèliarde, Brown Swiss e Rossa Svedese. Dalla prova è emerso che le frazioni proteiche del latte sono influenzate da alcune fonti di variazione come lo stadio di lattazione e l’ordine di parto; la razza in vece influenza in particolar modo κ-CN, α-La e β-Lg, frazioni proteiche tra loro intimamente associate. Tra gli schemi di incrocio, hanno presentato un’alta significatività le combinazioni con la razza Bruna e la Montbeliarde, la cui selezione o la presenza naturale rispettivamente dell’ allele B della κ-CN è di grande interesse per l’industria di trasformazione poichè porta ad un latte di qualità maggiore, dato il contenuto più alto di caseina totale. Tale metodo è stato in ultimo applicato per l’analisi di latte individuale proveniente da aziende che allevassero contemporaneamente almeno due delle sei razze scelte per la prova, tra specializzate e a duplice attitudine, cioè razza Holstein-Friesian, Brown Swiss, Jersey e Grigia Alpina, Pezzata Rossa e Rendena rispettivamente. Nella prova sono state considerate anche quattro diverse tipologie aziendali, cioè l’allevamento di tipo moderno, di tipo tradizionale con l’utilizzo di insilati, di tipo tradizionale senza la malga estiva, di tipo tradizionale originale. Anche in questo caso stadio di lattazione ed ordine di parto hanno influito notevolmente sulle frazioni proteiche oggetto di studio; tra razze, la Jersey si è distinta notevolmente dalle altre, proprio perché caratterizzata naturalmente da un latte di contenuto proteico notevolmente alto. Nella razza Grigia è stata inoltre identificata tramite cromatografia un’ulteriore probabile variante della κ-CN, anche se sarà necessario raccogliere maggiori informazioni servendosi anche di tecniche complementari o accoppiate all’HPLC. La tipologia aziendale di tipo tradizionale con uso di insilati è risultata essere la strategia migliore, dato il contenuto proteico molto alto riscontrato nel latte, anche se è risultata la strategia con anche il più alto numero di cellule somatiche; l’allevamento moderno inaspettatamente non ha dato le performances migliori, mentre l’allevamento tradizionale senza uso della malga è risultato il peggiore per quanto riguarda la componente proteica del latte.

In experiment one, week old Jersey bull calves (n=39) were assigned to one of four diets: 21/21 (n=8), 27/33 (n=8), 29/16 (n=9), MILK; or a baseline sacrifice group (n=6). Diets 21/21, 27/33, and 29/16 were milk replacers containing 21, 27, or 29% CP, and 21, 33, and 16% fat, respectively. Diet 21/21 was fed at 15% of BW. Diets 27/33, 29/16, and MILK supplied 180g CP/d. Calves were fed 4 wk. Weight, hip height, wither height, heart girth, and body length were measured weekly. Weekly plasma samples were analyzed for PUN, NEFA, and glucose. Calves were processed to estimate body composition. Feed efficiency and ADG were greatest for calves fed MILK, least for calves fed 21/21, and intermediate for calves fed 29/16 and 27/33. Calves fed 27/33 or MILK had the greatest gains of fat and percentage fat in the empty body. Body fat percentage of calves fed 29/16 or 21/21 was not changed by diet. Performance of calves fed 27/33 and 29/16 was similar except that calves fed 29/16 were leaner and calves fed 27/33 had a propensity for elevated NEFA. Feeding 180g of CP in the MR was beneficial to calf performance compared with diet 21/21. In experiment two, tissues from a subset of calves [21/21 (n=4), 27/33 (n=5), 29/16 (n=5), MILK (n=3), baseline (n=2)] were scanned using dual energy x-ray absorptiometry to estimate mass, fat, CP, and ash. Liver, organ, and carcass mass by DXA were correlated to scale weights (R²⁺= 0.99, 0.62, and 0.79, respectively). DXA was a poor predictor of percentage fat, CP, and ash (adjusted R²⁺ <0.10). Experiment three determined level of calf mortality in the United States; and identified opportunities to reduce mortality. Herds (n=88) were representative of the US Jersey population. Production averaged 7180 ± 757 kg milk annually. Herds averaged 199 births annually. Mortality was 5.0% from birth to 24 h (M24) of life and 6.7% from 24 h to 3 mo of life (M3). Level of mortality (M24) was highest in herds that calved on pasture. Lower levels of mortality (M3) were associated with use or maternity pens and earlier weaning.
Ph. D.

The objective of this thesis is to estimate genetic parameters and discover genes and genomic regions associated with milk yield, lactation curve traits (peak milk yield, days to peak milk yield and persistency) and milk composition (fat and protein percentage) in Thai and Australian dairy cattle. The data on Thai dairy cattle from three government farms were analysed. Cumulative 305- and 100-day milk yield was calculated by the Wood model and an adapted test-interval method. The heritability of 305-day milk yield, peak milk yield and protein percentage had moderate to high estimates ranging from 0.19 to 0.45 while days to peak milk yield, persistency and fat percentage have low heritability ranging from 0.08 to 0.14. High genetic correlations were found between 305- and 100-day milk yield (0.89), 305-day milk yield and peak milk yield (0.86) and days to peak milk yield and persistency (0.99). The data on Australian dairy cattle, provided by DataGene, were used for genetic analysis of the same traits as those of the Thai dataset. In addition, genotypic data on the Australian dairy cattle were included for the analysis. The estimated pedigree-based heritability by ASReml-R and the estimated SNP-based heritability by GCTA tools were compared. The heritability estimates for most of the traits were moderate to high ranging from 0.15 to 0.56. The heritability estimates from the pedigree-based analysis were lower than the SNP-based estimates for most of the traits except persistency and fat and protein percentages. In addition, GWAS of all the traits was conducted. The most significant SNPs and genes associated with a number of lactation traits were discovered on Chromosome 14.

Mice carrying mutated β-casein genes were created through gene targeting in embryonic stem cells using a replacement-type vector. β-casein was absent from the milk of homozygous mutant mice, and no mRNA was detectable from the mutant allele. The mutation was compatible with viability, fertility and lactation. The total protein concentration of β-casein-deficient milk was reduced, although the loss of β-casein was partially compensated by enhanced synthesis and/or secretion of other milk proteins. The pre-weaning growth of pups feeding β-casein deficient milk appeared to be slower, probably reflecting the reduction in the total milk protein concentration. The reduction (in heterozygotes) or absence (in homozygotes) of β-casein in milk resulted in smaller casein micelles, probably due to increases in the ratios of κ-casein to calcium-sensitive caseins. These results show that β-casein is dispensable in lactation. Targeting of subtle mutations is likely to be important for many purposes, including the manipulation of milk structure. The 'hit and run' method for targeting the subtle mutations would be facilitated by positive-negative selection during the first (targeted insertion) step. To explore the feasibility of negative selection in conjunction with insertion-type gene targeting vectors, the effects of placing terminal heterologies on a hypoxanthine phosphoribosyltransferase (HPRT) insertions vector were determined. The targeting was generally accurate but the targeting efficiency was reduced by terminal heterologies.

Distribution and bioavailability of ⁴⁷calcium in milk labeled by extrinsic and intrinsic methods was investigated. Milk from Sprague Dawley rats was labeled by both methods, and milk from a cow was labeled by the extrinsic method. Retention of ⁴⁷Ca from milks administered to young male Sprague Dawley rats was determined through whole body counting for 6 days after administration of milk. Percent of ⁴⁷Ca dose retained was 72% for extrinsically labeled cow milk, 62% for extrinsically labeled rat milk, and 55% for intrinsically labeled rat milk. Samples were fractionated by ultracentrifugation and by gel exclusion chromatography. ⁴⁷Calcium distributions in rat milk labeled intrinsically or extrinsically were similar. The majority of ⁴⁷Ca was found in a particulate, > 30,000 molecular weight fraction (about 60% for cow milk, about 90% rat milks). The amount of milk calcium retained by rats appeared to be related to the amount of noncasein micelle-associated calcium. When administered by intraperitoneal injection into rats, ⁴⁵Ca specific activity of milk peaked in 60 to 90 minutes. Specific activity was highest in cytosol, and lower in Golgi apparatus and rough endoplasmic reticulum. Specific activities in subcellular fractions changed in parallel with specific activities of milk. Rapid turnover of Ca was observed in endoplasmic reticulum and Golgi apparatus; this was expected since secretory proteins and associated Ca are transported through these organelles for secretion. In vitro ⁴⁵Ca accumulation was compared in Golgi apparatus and endoplasmic reticulum from liver and mammary gland of lactating Dunkin Hartley guinea pigs. In the presence of ATP, highest accumulation per unit total fraction protein was found in Golgi apparatus (mammary gland 28% of available ⁴⁵Ca, liver 11%) while 8% was accumulated by endoplasmic reticulum fractions. Calcium accumulation was not the result of binding, as preincubation of vesicles with calcium ionophore resulted in less than 10% of the accumulation found without ionophore. The ATPase inhibitor sodium orthovanadate, and the ATP analog AMP-PNP, reduced ⁴⁵Ca accumulation in all fractions. Protonophore caused a small reduction in ⁴⁵Ca accumulation in all cases. Citrate accumulation by fractions was not observed under conditions used for ⁴⁵Ca accumulation.
Ph. D.

The objective of this study was to evaluate the effect of two different feeding systems and of four different energy sources (Grain diet) on lactation characteristics and milk composition of dairy cattle. A total of 8,808,798 test-day records from 566,736 Holstein cows in 5,183 different herds, and 416,883 test-day records from 26,973 Ayrshire cows in 652 different herds covering a period of five years were obtained from the Quebec dairy herd improvement agency (Valacta). In addition to test-day records, information on lactation, animal status, feed composition and feeding systems was also available. For both Ayrshire and Holstein cows the fixed effect of Feeding System*DIMB (Blocks of 15 days in milk) was a significant effect in predictive models of daily milk, milk-fat, protein, and lactose yields and on milk urea nitrogen (MUN) concentration. Cows served a diet prepared with a Total Mixed Ration (TMR) compared to cows served a diet in a Traditional way tended to have higher peak milk yields and appeared to have a stronger persistency after peak milk yield. TMR-fed cows also showed a tendency for higher milk-fat, protein, and lactose yields and lower MUN concentrations than Traditionally-fed ones. Significantly higher milk yields (peak to 135 days in milk) and higher milk-fat and protein yields (peak to mid-lactation) were found in TMR-fed cows compared to Traditionally-fed ones in 3rd parity Holsteins. Both milk-fat and protein-yield lactation curves of TMR-fed cows displayed a different pattern than Traditionally-fed cows. The fixed effect of the Grain diet*DIMB was found to be a significant effect in predictive models of milk and milk-protein yields of both Ayrshire and Holstein. It was also found to be a significant effect in predictive model of MUN concentration but only in 2nd parity Ayrshire. The effect was non-significant in predictive models of both milk-fat or lactose yields. A tendency for higher milk and milk-protein yields, and lower MUN values was seen when cows received Corn Grain or High Moisture Corn compared to Barley or Commercial Concentrate but no significant differences were observed. It was concluded that a tendency for higher milk and components yields can be observed when cows are fed with a TMR compared to a Traditional system.

The purpose of this study was to investigate the effect of prepartum and postpartum nutrition on milk production of commercial beef cows. Forty-three Angus or Angus X Holstein females, ranging in age from 2 to 6 yr, were randomly assigned by age and percentage Holstein within age to one of two prepartum grazing treatments (PRE). All females, regardless of PRE, were assigned at calving to receive the same post-calving nutritional energy. Females were assigned at calving by age, percentage Holstein within age, prepartum nutritional treatment and calving date to one of two milking groups. Milk weight (grams), milk composition (fat, protein, lactose, solids-not-fat, somatic cell count), dam body condition score (1 to 9), dam body weight, dam backfat thickness, loineye area, calf weaning weight and postpartum interval to estrus were all evaluated. Milk removal occurred biweekly by vacuum milking machine after intravenous injection of 20 IU of oxytocin. Samples were weighed and taken for milk analysis and determination of milk components. At 76± 10 d post-calving, females were assigned by age, percentage Holstein within age, prepartum nutritional treatment, and calving date to receive one of two postpartum nutritional treatments (POST). Females continued to be milked by machine biweekly until calves were weaned 199 ± 10 d. Differences in grazing level prior to calving significantly effected calf birth weights, with dams on the prepartum restricted grazing being lighter in weight at birth, 36.69 ± .68 and 38.95 ± .81 kg for PRE-L and PRE-H groups, respectively, however grazing differences did not effect calf weaning weight, calf gain or calf average daily gain. POST nutritional treatments significantly effected all calf performance traits with 37.10±.70, 38.54±.88; 196.89±4.9, 213.33±6.2; 159.79±4.8, 174.78±6.0; .809±.024, .888±.030; for birth weight, weaning weight, calf gain and calf average daily gain from cows on the POST -M or POST -H nutritional treatments, respectively. Pre-partum nutrition effected milk production (P < .001) with dams from the PRE-L grazing group producing less milk, 5622 ± 75 vs 6888 ±80 g. Postpartum energy also effected milk production with dams on the POST-H energy level producing more milk than dams from the POST-M group. Percentages of fat, protein, lactose and solids-not-fat were not different between the prepartum or postpartum diets (P>. 10). Somatic cell count was negatively correlated with dam milk production (P< .03). Postpartum interval to estrus was shorter for the PRE-L group than for the PRE-H, 43 ± 4 vs 53 ± 4 d.
Master of Science

Background: Breast milk is the principal source of nutrition during a critical period of immune programming - maternal and environmental exposures may influence breast milk composition and infant health. Objectives: To examine whether environmental and/or maternal factors influence levels of immune active components in colostrum and breast milk and identify associations between these factors and health outcomes. To examine if colostrum/breast milk immune composition can be grouped into specific 'lactotypes'. Methods: A prospective cohort study of mother/infant pairs in London, Moscow and Verona. Colostrum samples (days 0-6) and Mature Breast Milk (4-6 weeks) were analysed in duplicate using electrochemiluminescence, and the relationship between levels of immune active factors and maternal/environmental/infant factors was evaluated using mixed models. Lactotypes were identified using Principal Components Analysis. Results: Levels of immune active cytokines and growth factors in colostrum declined rapidly over time (r=-0.39 to -0.16; p<0.01). The effect of time could not be corrected using total protein or sodium as correction factors, due to different kinetics for each mediator measured. There were significant differences in colostrum and breast milk composition between countries, which could not be explained by the environmental and maternal factors examined. Using PCA there were two clusters of mediators, suggesting that four human breast milk 'lactotypes' exist, based on immune composition. There was some evidence in support of a relationship between human milk mediator levels and/or lactotypes, and infant health outcomes. Conclusions: The data support an important role for breast milk cytokines, and especially growth factor, levels as determinants of infant health. Further work is needed to identify improved methods for analysing colostrum and mature milk composition, which account for time of collection and/or stage of lactation.

Lactation provides the singular source of nourishment to the offspring of mammals. This nutrition source also contains a diverse microbiota affecting the development and health of the newborn. Here, we examined the milk microbiota in water deer (Hydropotes inermis, the most primitive member of the family Cervidae), reindeer (Rangifer tarandus, the oldest semi-domesticated cervid), and the dairy goat (Capra aegagrus, member of the family Bovidae), to determine if common milk microbiota species were present across all three ruminant species. The results showed that water deer had the highest bacterial diversity, followed by reindeer, and then goat. Unifrac distance and correspondence analyses revealed that water deer harbored an increased abundance of Pseudomonas spp. and Acinetobacter spp., while milk from reindeer and goat was dominated by unclassified bacteria from the family Hyphomicrobiaceae and Bacillus spp., respectively. These data indicate significant differences in the composition of milk-based bacterial communities. The presence of Halomonas spp. in three distinct co-occurrence networks of bacterial interactions revealed both common and unique features in milk niches. These results suggest that the milk of water deer and reindeer harbor unique bacterial communities compared with the goat, which might reflect host microbial adaptation caused by evolution.

Milk production has a strong effect on fertility and at the same time reproduction affects the milk composition. In the last decade, special interest has arisen in studying milk composition and its relation with health, efficiency, and fertility. Therefore the principal objective of this thesis was to assess the relationships between the fertility of dairy cows and their milk yield, composition, and infrared spectra. Data used were collected by the Breeders Federation of Alto Adige/Südtirol from the northeastern Italian province of Bolzano/Bozen. The milk’s data comprises production, composition and physical properties. For fertility, all the insemination dates were available as well as the calving date. The milk samples collected were analyzed using a MilkoScanTM FT+ 6000 (Foss Electric, Hillerød, Denmark), the spectrum covered 1,060 wavenumbers (wn) from 5,010 to 925 cm-1. Four breeds were studied: the specialized dairy breeds Holstein and Brown Swiss and the double purpose breeds Simmental and Alpine Grey. The effects of breed and its interaction with milk productivity at the herd level (Herd-L) and at cow-within-herd level (Cow-L) on fertility traits in dairy cattle were studied in the second chapter. A mixed model was fitted to establish milk production levels of the various herds and individual cows according to milk yield. The interval calving-first service (iCF), interval first service-conception (iFC) and days open (DO) traits were analyzed using a Cox’s proportional hazards model. The non-return rate at 56d after first service (NRR), pregnancy rate at first service (PRF) and the number of inseminations (INS) traits were analyzed using a logistic regression. It was observed a strong interaction between breed and productivity class at both Herd-L and Cow-L on all traits. The dual-purpose Simmental and Alpine Grey breeds had better fertility than the specialized Holstein and Brown Swiss dairy cows, also at the same daily milk yield, and the effects of herd and cow productivity differed from each other and differed among breeds. In conclusion, greater herd productivity can result in higher fertility in cows, while a higher milk yield of individual cows within a herd results in lower fertility. These effects at both Herd-L and Cow-L are curvilinear and stronger in the dual-purpose breeds, being more evident from the low to the intermediate levels than moving from the intermediate to the high productivity classes. The relationships between the estrous cycle phases in dairy cattle to milk composition, milk physical indicators and milk fatty acids were assessed in the third chapter. The test days around the first insemination after calving in the range from -10 to +10 days were selected and classified in 5 phases: Diestrus high-progesterone (Diestrus-HP) from -10 to -4 d; Proestrus from -3 to -1 d; Estrus day 0 (insemination day); Metestrus from 1 to 2 d; and Diestrus increasing-progesterone (Diestrus-IP) from 3 to 10 d. A mixed model was fitted to analyze the milk components and the milk physical indicator properties, including the effect of the estrous phases and we estimated the contrasts among them. The milk composition showed high variability among the estrous phases, affecting principally the fat, protein and lactose. The fatty acid profile and the physical indicators were also highly affected indicating important differences occasioned by the hormonal and behavioral changes of cows in estrus. The predictive abilities of fat, protein, lactose, casein, and FTIR spectral data to predict cow’s pregnancy status (PS) were assessed in the fourth chapter. We used generalized linear models to predict PS using fat, protein, lactose, casein and single FTIR spectral bands. We also fitted a Bayesian variable selection model to predict PS using the complete FTIR spectrum. Prediction accuracy was evaluated using a 10 fold cross-validation study and calculating the area under a receiver operating characteristic curve (CV-AUC) based on phenotypic predictions and observations. Overall, the most prediction accuracies were obtained for a model that included the complete FTIR spectral data. Alpine Grey cows had the highest CV-AUC (0.645), while Brown Swiss and Simmental had similar results (0.630 and 0.628 respectively) and Holsteins had the lowest value for FTIR Spectra (0.607). For the single wavelength analyses, important peaks were detected at: from wn 2,973 to wn 2,872 cm-1 where Fat-B is usually filtered; wn 1,773 cm-1 where Fat-A is filtered; wn 1,546 cm-1 where protein is filtered; wn 1468 cm-1 associated with urea and fat; wn 1,399 cm-1 and wn 1,245 cm-1 associated with acetone; from wn 1,025 cm-1 to wn 1,013 x cm-1 where lactose is filtered. This research provides new insights to alternative strategies for pregnancy status screening on dairy cattle.
La produzione di latte ha un forte effetto sulla fertilità delle bovine e allo stesso tempo la riproduzione influisce sulla composizione del latte. Negli ultimi decenni, si è sviluppato un particolare interesse riguardo lo studio della composizione del latte e del suo rapporto con la salute, l'efficienza e la fertilità. Pertanto l'obiettivo principale di questa tesi è stato quello di valutare i rapporti tra la fertilità delle bovine da latte e la loro produzione di latte, la composizione e gli spettri a infrarossi del latte prodotto. I dati utilizzati sono stati raccolti dalla Federazione Allevatori dell’ Alto Adige / Südtirol di Bolzano / Bozen in Italia. I dati relativi al latte comprendono la produzione, la composizione e le proprietà fisiche. Per la fertilità, sono state considerate tutte le date di fecondazione e il giorno di parto. I campioni di latte raccolti sono stati analizzati utilizzando un MilkoScanTM FT + 6000 (Foss Electric, Hillerød, Danimarca), e lo spettro ricopriva 1,060 lunghezze d’onda, da 5,010 a 925 cm-1. Sono state utilizzate quattro razze: le razze specializzate Frisona e Bruna, e le razze a duplice attitudine Pezzata Rossa e Grigio Alpina. Nel secondo capitolo sono stati studiati gli effetti della razza e la sua interazione con la produzione di latte a livello di allevamento (Herd-L) e a livello individuale (di vacca entro allevamento) (Cow-L) sui caratteri di fertilità nelle bovine da latte. Per stabilire i livelli di produttività delle varie aziende e delle singole vacche, in base alla produzione di latte, è stato utilizzato un modello misto. L’intervallo dal parto alla prima inseminazione (iCF), l'intervallo dalla prima inseminazione al concepimento (iFC) e l’intervallo parto concepimento (DO) sono stati analizzati utilizzando un modello di rischio proporzionale di Cox. Il tasso di non ritorno a 56 giorni dopo il primo servizio (NRR), il tasso di gravidanza al primo servizio (PRF) e il numero di inseminazioni (INS) sono stati analizzati utilizzando una regressione logistica. Per tutti i caratteri è stata osservata una forte interazione tra la razza e la classe di produttività, sia a livello di allevamento che a livello individuale. Le razze a duplice attitudine Pezzata Rossa e Grigio Alpina hanno una migliore fertilità rispetto alle vacche da latte specializzate di razza Frisona e Bruna, anche a parità di produzione, e gli effetti della produttività aziendale e individuale differivano tra loro e tra le razze. In conclusione, una maggiore produttività dell’ azienda può determinare una maggiore fertilità nelle vacche, mentre una maggiore produzione di latte delle singole vacche all'interno di una azienda può risultare in una minore fertilità. Questi effetti, sia livello di allevamento che a livello individuale, hanno un andamento curvilineo e sono più forti nelle razze a duplice attitudine, essendo più evidenti passando da una produttività bassa a una intermedia, piuttosto che passando dal livello intermedio alle classi di produttività elevata. Nel terzo capitolo sono state valutate le relazioni tra le fasi dell’estro nei bovini da latte e la composizione, gli indicatori fisici e gli acidi grassi del latte. I giorni di campionamento attorno alla prima inseminazione dopo il parto, nell'intervallo da -10 a +10 giorni, sono stati selezionati e classificati in 5 fasi: diestro-alto progesterone (Diestrus-HP) da -10 a -4 giorni; proestro da -3 a -1 giorni; giorno di estro 0 (giorno di inseminazione); metestro da 1 a 2 giorni; e diestro-progesterone in aumento (Diestrus-IP) da 3 a 10 giorni. Per analizzare i componenti del latte e gli indicatori fisici delle proprietà del latte è stato usato un modello misto, includendo l'effetto dell’a fase estrale, e abbiamo stimato i contrasti tra di essi. La composizione del latte ha mostrato un'elevata variabilità tra le fasi diverse dell’estro, e i caratteri maggiormente influenzati sono stati il grasso, la proteina e il lattosio. Anche il profilo acidico e gli indicatori fisici sono stati notevolmente influenzati, indicando importanti differenze causate dalle modifiche ormonali e comportamentali delle bovine in estro. Nel quarto capitolo è stata valutata l’abilità di predizione dello stato di gravidanza delle vacche (PS) utilizzando grasso, proteina, caseina, lattosio e gli spettri FTIR . Per predire lo stato di gravidanza sono stati utilizzati modelli lineari generalizzati utilizzando grasso, proteina, lattosio, caseina e le singole lunghezze d’onda FTIR. È stato inoltre fittato un modello Bayesiano di selezione di variabile per predire lo stato di gravidanza utilizzando lo spettro FTIR completo . L’accuratezza di predizione è stata valutata utilizzando uno studio di validazione incrociata ripetuto 10 volte e calcolando l'area sotto a la curva del -receiver operating characteristic- (CV-AUC) basata sulle predizioni fenotipiche e sulle osservazioni. Nel complesso, le migliori accuratezze di predizione sono state ottenute per un modello che includeva i dati spettrali FTIR completi. Le vacche Grigio alpine hanno ottenuto il più alto CV-AUC (0.645), Brune e Pezzate Rosse hanno ottenuto risultati simili (0.630 e 0.628 rispettivamente), mentre le Frisone hanno ottenuto il valore più basso per gli spettri FTIR (0.607) completi. Per le singole analisi di lunghezza d'onda, picchi importanti sono stati rilevati: da wn 2,973 a wn 2,882 cm-1 corrispondente al filtro Fat-B delle analisi con monocromatore; wn 1,773 cm-1 dove è posizionato il filtro grasso-A; wn 1,546 cm-1 dove è posizionato il filtro della proteina; wn 1,468 cm-1 che è associato a urea e grasso; wn 1,399 cm-1 e wn 1,245 cm-1 associati con l’acetone; da wn 1,025 cm-1 fino a 1,013 x cm-1 dove è posizionato il filtro del lattosio. Questa ricerca fornisce nuove conoscenze riguardo a strategie alternative per lo screening dello stato di gravidanza dei bovini da latte.

Mestrado em Engenharia Zootécnica - Produção Animal - Instituto Superior de Agronomia
The purpose of this study was to characterize the milk used in the manufacture of Azeitão cheese, in particular the physico-chemical properties, hygiene and technological aptitude, given the influence of milk quality in cheese making. Sampling took place from February to May and samples from raw milk sheep for the manufacture of Azeitão cheese, consisting of individual milk (one producer) or mixed (from different producers) milk, were analyzed for composition, hygiene and parameters for the assessment of the milk clotting behavior, such as clotting time, micellar aggregation properties and gel firmness. The effect of the milk producer was very significant (p <0.01) at both the physical-chemical composition, hygiene and technological aptitude, and the effect of month of production was significant only for protein content and consistency of curd. In general, the milk showed poor hygienic quality and low protein content, with negative repercussions in cheese making behaviour

This study was to evaluate effects of milk replacer (MR) composition on: mass and composition of mammary parenchyma (PAR) and fat pad (MFP), growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis gene expression, and putative mammary epithelial stem cells. The hypothesis was that diet during the pre-weaning period alters the development, persistence, or activity of populations of putative mammary epithelial stem cells, possibly through involvement of GH/IGF-I axis molecules. Twenty-four newborn heifers were fed one of four MR diets: CON (20% CP, 21% fat MR fed at 441 g DM/d), HPLF (28% CP, 20% fat MR fed at 951 g DM/d), HPHF (27% CP, 28% fat MR fed at 951 g DM/d), and HPHF+ (27% CP, 28% fat MR fed at 1431 g DM/d). Animals were harvested on d 65 of life and mammary tissue was subjected to biochemical, molecular, and histological examination. By design, the effects of diet were evaluated at a common chronological age, but not necessarily at the same physiological age (body weight). Results from heifers reared on CON were compared to the average results from heifers reared on the other 3 diets. The second comparison evaluated the effect of increased fat in MR when protein content and intake were the same. The final comparison evaluated the effect of increased intake of a high-fat, high-protein MR. Neither diet composition nor nutrient intake in pre-weaned heifers affected PAR weight, PAR composition, GH/IGF-I axis gene expression, or putative mammary epithelial stem cell abundance when assessed at a common chronological age. Changes in MFP size and composition were observed, but no diet effect on GH/IGF-I axis gene expression in MFP was observed. This suggests nutrition is not critical for regulating the expression of local GH/IGF-I axis components or stem cell populations in the developing heifer mammary gland.
Ph. D.

Afin de répondre à la diversification des objectifs de la filière laitière (ex. efficacité alimentaire, santé et longévité des animaux, etc.), et ceci dans un contexte de forte volatilité des prix du lait et des intrants, la quantification des réponses multiples aux changements de régimes alimentaires représente un intérêt afin d’aider les producteurs laitiers à optimiser la ration des animaux. Le principal objectif de ce travail a consisté à développer et évaluer un modèle de prédiction des réponses de l’ingestion, de la quantité et composition du lait aux changements de régimes alimentaires chez la vache laitière. Une méta-analyse a ainsi été appliquée sur une grande base de données de la littérature afin de quantifier la réponse de l’ingestion aux régimes, et les réponses laitières (quantité totale, sécrétion des composants du lait et composition du lait) aux changements d’énergie nette (UFL) et protéines métabolisables (PDI) de la ration. Un élément clé dans le développement de ces équations de réponses était qu’elles soient applicables à travers différent potentiel laitier. Ceci a pu être atteint en exprimant les apports PDI et UFL par rapport à une situation nutritionnel pivot, qui correspond à une efficacité d’utilisation des PDI de 67% et une efficacité d’utilisation des UFL par lait de 100% (équivalente à un bilan énergétique nul). Construite à partir des efficacités PDI et UFL, une approche a été proposée pour estimer les apports PDI et UFL à la situation pivot, à partir desquels les équations de réponses peuvent s’appliquer. Evalué sur deux jeux de données indépendants, cette approche a permis de prédire les réponses de production laitière, productions de matières grasses, lactose et protéines du lait aux changements d’apports PDI et UFL avec une bonne précision pour des rations considérablement différentes, et à travers différents stades de lactation. Dans un autre modèle, les effets du stade physiologique (stade de lactation, stade de gestation, croissance) sur les performances animal, i.e. production laitière, productions de matières grasses, lactose et protéines du lait, changement de composition corporelle et ingestion, ont été quantifiés à travers des animaux de potentiel laitier différent. Il a été constaté que la structure du modèle était adéquate pour simuler les performances de différentes races laitières (Holstein, Rouge Danoise et Jersiaise). Afin de prédire les conséquences d’un changement alimentaire sur le long terme, les équations de réponses, centrées sur la situation nutritionnel pivot, ont été intégrées au sein du modèle dynamique. Cette intégration a pu se faire en appliquant le concept du pivot au modèle dynamique afin d’obtenir des courbes pivot, à partir desquelles les lois de réponses s’appliquent. Le modèle construit est le premier à intégrer les deux grands types de régulation biologique (homéostase et l’homéorhèse) chez la vaches laitière permettant de prédire les performances animales à partir d’une définition précise du potentiel laitier
In order to better cope with the increasing diversity of objective in dairy production (e.g. feed efficiency, animal health, animal longevity, etc.) in a context of high volatility of feed and milk prices, quantification of animal’s multiple responses to dietary changes is of particular interest to help dairy farmers in optimizing the diet. The main aim of the present study was to develop and evaluate a model to predict the responses in dry-matter intake, milk yield, milk component yields and contents to changes in dietary composition in dairy cows. A meta-analysis of the literature was conducted to quantify dry-matter intake response to changes in diet composition, and milk responses (yield, milk component yields and milk composition) to changes in dietary net energy (NEL) and metabolizable protein (MP) in dairy cows. A key point in the development of these response equations was that they could be apply on animals of varying production potential. This was achieved by expressing MP and NEL supply relative to a pivot nutritional status, defined as the supply of MP and NEL resulting to MP efficiency of 0.67 and NEL efficiency of 1. Based on MP and NEL efficiency, an approach was proposed to estimate the pivot MP and NEL supplies, around which the response equations can be applied. Evaluated with two independent datasets, this approach predicted milk yield and milk component yields responses to change in MP and NEL supply with a good accuracy for diets that are substantially different, and across all stages of lactation. In another model, the effect of physiological status (lactation stage, gestation, growth) on animal performance, i.e. milk yield, milk component yields, body composition change and dry-matter intake, were quantified across a range of animal potential. It was found that the model structure was adequate to simulate performance of different dairy breeds (Holstein, Danish Red and Jersey). To predict the long-term consequences of a dietary change, response equations, centred on the pivot nutritional status, were integrated into the dynamic model. This integration has been possible by applying the pivot concept into the dynamic model. This way, lactation pivot curves were calculated, from which response equations are applied. The model built is the first to integrate the two major biological regulations (homeostasis and homeorhesis) in dairy cows that predicts animal performance using a precise definition of milk potential

La présente étude visait à identifier, en explorant la fraction protéique des laits de camélidés provenant de plusieurs régions du Kazakhstan, des molécules originales (peptides, protéines) potentiellement responsables des propriétés attribuées au lait de chamelle. Près de 180 échantillons de lait de 2 espèces de camélidés (Camelus bactrianus, C. dromedarius et leurs hybrides) ont été collectés à différents stades de lactation, âge et nombre de vêlages, et soumis à différentes techniques analytiques et approches protéomiques (SDS-PAGE, LC-MS/MS et LC-ESI-MS). Cinquante molécules protéiques correspondant à des variants génétiques, des isoformes issues de modifications post-traductionnelles et d'épissages différentiels, appartenant à 9 familles de protéines (κ-, αs1-, αs2-, β- et γ-CN, WAP, α-LAC, PGRP, CSA / LPO) ont été caractérisées. L’existence de deux isoformes inconnues (i1 et i2) de la caséine αs2 a été observée dans les deux esèces. Ces isoformes sont des variants d'épissage consécutif pour l’un à l’intégration d'une séquence de 27 nucléotides « in frame », codant pour le nonapeptide ENSKKTVDM, dont la présence a été confirmée au niveau génomique, flanquée de motifs canoniques définissant une structure exonique. La seconde isoforme, présente à différents niveaux de phosphorylation compris entre 8P et 12P, comporte un décapeptide supplémentaire (VKAYQIIPNL), révélé par LC-MS/MS, codé par une extension 3 'de l'exon 16. En outre, nous rapportons, pour la première fois à notre connaissance, l’existence d'une isoforme de phosphorylation de la caséine αs2 présentant au moins un résidu S/T phosphorylé n’appartenant pas à la séquence canonique habituelle (S/T-X-A) reconnue par la kinase mammaire, suggérant ainsi l'existence de deux systèmes impliqués dans la phosphorylation des caséines, dans la glande mammaire.S’agissant de la WAP, nous avons identifié chez C. bactrianus un nouveau variant génétique (B), issue d'une transition G => A conduisant à un changement de codon (GTG/ATG) dans la séquence nucléotidique de l’ARNm, qui entraine un changement d’acide aminé en position 12 de la protéine mature (V12M). Un variant résultant de l’usage du site d'épissage canonique, reconnu comme tel chez les autres mammifères exprimant la WAP dans leur lait, a été identifié. La forme majoritaire de la WAP cameline, décrite pour la première fois par Beg et al. (1986) qui présente une insertion de 4 résidus d'acides aminés (56VSSP59) dans le segment peptidique reliant les deux domaines 4-DSC, résulte de l'utilisation d'un site d'épissage cryptique intronique improbable, prolongeant l'exon 3 du gène de 12 nucléotides sur son extrémité 5 '. De plus, nous confirmons que chez les camélidés, l'intron 3 du gène spécifiant la WAP, est un intron rare de type GC-AG, avec un site donneur faible qui s’accompagne d’un effet compensatoire au site consensus de l'exon accepteur.Finalement, en utilisant un protocole optimisé, nous avons isolé les vésicules extracellulaires (VE) dérivés du lait de camélidés présentant les caractéristiques morphologiques, de taille et de contenu en protéines des exosomes. Nous avons identifié un millier de protéines différentes représentant le premier protéome des VE dérivés du lait de chamelle qui semble plus étendu que le protéome du lait de chamelle, incluant notamment les marqueurs associés aux VEs, tels CD63, CD81, HSP70, HSP90, TSG101 et ADAM10. Nous avons également identifié des protéines présentes dans d'autres compartiments du lait. C'est notamment le cas pour les protéines apparentées à Ras, MFG-E8, ou CD9 qui sont également présentes dans les globules gras du lait. Nos résultats suggèrent par ailleurs fortement que les VEs dérivés du lait de chamelle ont des origines cellulaires différentes
The present study aimed to identify, in exploring the protein fraction of camelid milks from several regions of Kazakhstan, original molecules (peptide, proteins) potentially responsible for the properties attributed to camel milk. Nearly 180 milk samples from two camel species (Camelus bactrianus and C. dromedarius, and their hybrids) we collected at different lactation stage, age and calving number, and submitted to different proven analytical techniques and proteomic approaches (SDS-PAGE, LC-MS/MS and LC-ESI-MS). A detailed characterization of 50 protein molecules, relating to genetic variants, isoforms arising from post-translational modifications and alternative splicing events, belonging to 9 protein families (κ-, αs1-, αs2-, β-; and γ-CN, WAP, α-LAC, PGRP, CSA/LPO) was achieved. We reported the occurrence of two unknown isoforms (i1 and i2) of camel αs2-CN arising from alternative splicing events. Using cDNA-sequencing, i1 was characterized as a splicing-in variant of an in-frame 27-nucleotide sequence, of which the presence at the genome level, flanked by canonic motifs defining an exon 13 encoding the nonapeptide ENSKKTVDM, was confirmed. Isoform i2, which appeared to be present at different phosphorylation levels ranging between 8P and 12P, was shown to include an additional decapeptide (VKAYQIIPNL), revealed by LC-MS/MS, encoded by a 3’-extension of exon 16. In addition, we reported, for the first time to our knowledge, the occurrence of a αs2-CN phosphorylation isoform with at least one phosphorylated S/T residue that does not match with the usual canonic sequence (S/T-X-A) recognized by the mammary kinase, suggesting thereby the existence of two kinase systems involved in the phosphorylation of caseins in the mammary gland.As far as camel WAP is concerned, we identified in C. bactrianus a new genetic variant (B), originating from a transition G => A, leading to a codon change (GTG/ATG) in the nucleotide sequence of cDNA, which modifies a single amino acid residue at position 12 of the mature protein (V12M). In addition, we describe the existence of a splicing variant of camel WAP, arising from an alternative usage of the canonical splice site recognized as such in the other mammalian species expressing WAP in their milk. We also report that the WAP isoform predominantly present in camelids milk, first described by Beg et al. (1986) as displaying an additional sequence of 4 amino acid residues (56VSSP59) in the peptide segment connecting the two 4-DSC domains, results from the usage of an unlikely intron cryptic splice site, extending camel exon 3 on its 5’ side by 12-nucleotides. In addition, we confirm that in the camel gene encoding WAP, intron 3 is a GC-AG intron, with a GC donor site showing a compensatory effect in terms of a dramatic increase in consensus at the acceptor exon position.Finally, using an optimized protocol, we isolated camel milk-derived EVs satisfiying the typical requirements for exosomal morphology, size and protein content. We identified a thousand of different proteins representing the first comprehensive proteome of camel milk-derived EVs that appears wider than camel milk proteome, including markers associated with small extracellular vesicles, such as CD63, CD81, HSP70, HSP90, TSG101 and ADAM10. We also identified proteins present in other milk components. This is particularly the case for lactadherin/MFG-E8, Ras-related proteins or CD9 that have been reported to occur in MFG. Our results strongly suggest that milk-derived exosomes have different cellular origin

[Truncated abstract] Mothers who deliver prematurely often have a delay in lactogenesis II and subsequent milk supply. Furthermore, due to the inability of their babies to breastfeed immediately after birth, these mothers are 'pump dependent' during both initiation and establishment of lactation. Apparently, there are no evidence based guidelines for the expression regime but some data suggesting that expression regimes for both breasts should be at least five times per day and at least 100 minutes expressing time per day. The project was set out to document the self selected current expression regimes of the preterm mothers from day 10 to 60 postpartum. It defined how various aspects of breast expression, such as frequency and interval, impact on the synthesis and production of milk. In addition, it determined the variations in the composition of preterm mother's milk. The collection of 24hr expression data and milk samples at each expression of each breast, each day, of 25 preterm mothers (<32 gestation age) from the neonatal intensive care unit in King Edward Memorial Hospital, Western Australia on day 10, 15-20, 30, 40, 50 and 60 postpartum showed that during the 'pump dependent' period (day 10 20), the frequency of expression for both breasts was 6, 6-7, 3-9 times per day (median, IQR, range) and total duration with the pump was 115, 80-160, 32-320 minute per day (median, IQR, range). Furthermore, during the 'transition from exclusively expressing to exclusively breastfeeding' period (day 30-60), frequency of expression/breastfeed and total duration of milk removal (both expressing and breastfeeding) for both breasts were 6, 5-7, 1-9 and 135, 75-170, 25-320, respectively (median, IQR, range). ... These nutrients make up the energy content of milk, thus the energy content of milk also varied greatly between mothers. Therefore, milk from individual preterm mothers varies greatly for individual values for fat, total protein, lactose and energy and this should be taken into account when calculating the level of fortification required for individual babies. The results suggest that when fortifying mother's milk, weekly measurement of fat and protein in milk would provide good estimates on which to base fortification requirements. The concentration of sIgA plus lactoferrin formed 32% of the total proteins in breastmilk. However there was large variations in the concentration of sIgA and lactoferrin (median, IQR, range: 0.82, 0.59-1.13, 0.05-2.93g/l and 2.41, 1.52-3.52, 0.04-8.82g/l, respectively) between mothers. Therefore the level of protection provided by these two proteins could differ greatly between babies. Further research on the relationship between the concentration of sIgA and lactoferrin in milk and the onset of infection would indicate the minimum amount of these proteins needed for the babies to benefit from the immune protection provided by their mother's milk. The hourly breast expression method and regression analysis of actual milk yield and interval since previous expression provides information that identifies the potential milk synthesis capacity of the breasts of the mothers and the impact of the interval between expressions on the milk production of the mothers. This information can be applied to individualize the interval between expression regimes to optimise milk production and minimize the demand on the mother. In addition, determining the changes in the milk composition of individual mothers would provide a more precise base to fortify their milk for their preterm babies.

The quality of early milk produced by dams is affected by various factors (i.e. breed, age, parity, environment, nutrition, management). The impact of these factors on the quality of milk then have subsequent effects on calf health and development. Producers are responsible for following guidelines in order to ensure that they feed calves optimal quality milk in order to produce a healthy animal. They can also regulate factors such as environment and nutrition of the dam in order to produce better quality early milk. However, even after maximizing these factors there is still high mortality rate among pre-weaned calves, therefore, other factors such as mode of birth and genetics need to be studied to determine impacts on early milk quality and make further improvements to calf health and decrease mortality. Two experiments were conducted in order to study the effects of maternal and genetic factors on early milk production and to determine relationships that exist with calf health. The objective of the first study was to determine the effects that the mode of delivery had on early milk composition, and on the rumen microbiome of calves. We hypothesized that mode of birth would impact early milk composition, and, in turn, influence the microbial phyla in the calf gut. The second study had three objectives: 1) establish phenotypic relationships between colostrum composition traits, milk production traits, and calf health, 2) determine impact of breed and season on colostrum production and 3) ) elucidate the genetic parameters (i.e. heritability, genotypic, and phenotypic correlations) among colostrum production and milk production We hypothesized that colostrum composition and production differ among breeds and by season and that individual components influence calf health. Additionally, we hypothesized that colostrum quality traits (i.e. Brix score and volume) are heritable. For the first study Charolaise (CHAR; n = 23) and Angus (ANG; n = 15) dams were divided into two experimental groups; dams underwent vaginal (VD; n= 25) or cesarean (CD; n= 13) deliveries. Early milk samples were collected and quantified for protein, lactose, somatic cell count, and fatty acid concentrations. After parturition calves were separated based on dams experimental group. Rumen fluid was collected from calves on d 1, 3, and 28 post-partum. Extracted DNA from fluid were used for metagenomic sequencing (ANG calves, n=11; CHAR calves, n=13). Samples were run on the HiSeq 2500 platform as paired end reads according to Ilumina's standard sequencing protocol. A regression analysis was done in SAS using PROC GLM and regressing mode of birth on milk components for d 1,3, and 28. After, milk components found to be significantly impacted by mode of birth were regressed against microbial counts. Results showed that VD dams were more likely to have increased (P  0.05) protein, solids non-fat, and lactose on d 1 and 3, but decreased (P < 0.05) urea concentrations. Similarly, short, medium, and long-chain fatty acids were increased (P  0.05) in VD d 3 milk. Changes in true protein elicited a decrease (P  0.05) in rumen fluid Actinobacteria and Proteobacteria; whereas, both solids non-fat and lactose were associated with an increased (P  0.05) response in d 1 transition milk. No significant results for d 28 of sampling were observed. Based on our results we suggest that mode of birth influences protein concentrations in early milk. However, only a slight impact on the overall dynamics of the calf rumen was observed with the microbiome remaining relatively stable on the phyla level in response to changes in protein concentration. The second study looked into relationships between colostrum composition traits, management practices, and calf health, as well as determined heritability and genetic correlations for colostrum quality traits. Values for test-day milk, protein, fat, and somatic cell count (SCS) for Holstein (HO, n= 250) and Jersey (JE, n=289) cows were obtained from the Animal Genomic and Improvement laboratory server at the USDA. Brix score, colostrum weight, dam age, parity, and 3-month season of calving were also recorded. After, colostrum samples from JE cows were sent to DHIA where compositional measurements were obtained (i.e. true protein, fat, lactose, SCS, solid non-fats). Lactoferrin concentration for JE colostrum samples was also determined via ELISA. Calf blood samples were collected within 72 h post-partum and total serum protein (TSP) quantified to determine success of passive immunity transfer. Additionally, farm staff were instructed to record colostrum source for 1st feeding (i.e. dam, mix, other), freshness for 1st feeding (frozen vs fresh), Brix score of colostrum fed, volume of colostrum fed, and birth weight. A PROC Mixed with LSMEANS was performed in SAS to determine relationships between colostrum components, test day components, and quality traits for season, breed, and the interaction between season and breed. Also, PROC Mixed with LSMEANS was used to determine relationships of calf health with environment, management, and colostrum components. Additionally, a Pearson correlation was used to determine relationships between colostrum components and quality traits. Results for Holstein and Jersey showed that both colostrum Brix and volume (P < 0.001) differed by breed. Colostrum volume (P < 0.001), lactose (P < 0.001), and lactoferrin (P = 0.002) varied significantly by season. Additionally, test day milk (P = 0.046), fat (P = 0.012), and protein (P = 0.003) varied significantly by season. Moreover, a significant season and breed interaction (P = 0.028) was observed solely for colostrum volume. Calf health models indicated that TSP, colostrum total protein and solid non-fats impacted incidence of respiratory illness, but no factor significantly impacted incidence of scours. Results for Pearson correlation indicated strong correlations between true protein and solid non-fats and Brix (r = 0.99; 0.86). Lactoferrin also had moderate negative correlations with volume and lactose (r = -0.35; -0.33). Heritability and repeatability's were calculated using BLUPF90 family of programs. A single-trait repeatability animal model was used and included a 1-vector phenotype (Brix or Colostrum weight), fixed effects (i.e. calving year, parity, 3-month season of calving, and age at calving), additive genetic variance, random permanent environment effects, and random residual effects. A series of bivariate models were used to calculate genetic correlations of Brix score and colostrum weight with test-day compositional traits. Heritability estimates results for Holstein cow Brix and colostrum weight, were 0.25 and 0.15. Jersey cow heritability estimates were 0.36 and 0.47 respectively. We also observed some significant genetic correlations with Holstein Brix score and test-day milk (-0.23), fat (0.54), and SCS (0.29) having moderate correlations. Holstein colostrum weight had a strong correlation with test-day milk (0.96). Jerseys had strong genetic correlation of Brix score with colostrum weight (-0.98). Low to moderately heritability was observed for Brix score and colostrum weight in both breeds making them receptive to genetic selection in order to improve breeding programs. In conclusion, mode of birth significantly impacted colostrum composition which had subsequent effects on abundance of rumen microbiota. Colostrum Brix and volume were impacted by breed, season, and interaction, and calf incidence of disease was impacted by colostrum composition and environment. Additionally, two factors influencing colostrum quality (Brix score and colostrum weight) were found to be low to moderately heritable and have moderate to strong genetic correlations to compositional traits. Strong significant relationships were also found between colostrum compositional traits and colostrum quality traits. Therefore, incorporating quality traits into breeding programs has the potential to influence compositional traits which, in turn, can impact calf health and development by the interactions that exist between composition and microbial abundance in the rumen.
Master of Science in Life Sciences
Factors like breed, age, parity, nutrition, environment, and management can affect the quality of early milk produced. Many of these factors have been studied and guidelines developed in order to ensure producers feed the best quality milk to their calves which will allow for calves to develop properly. However, there is still a high mortality rate in pre-weaned calves and factors like mode of birth and genetics have not been readily studied. The purpose of our studies were to determine mode of birth impacts on composition of early milk and establish relationships between composition and rumen microbial phyla abundance. Additionally, establish relationships between colostrum composition traits, management practices, and calf health, and determine heritability and genetic correlations of colostrum quality traits to test-day composition traits. Our hypothesis was that colostrum quality traits such as Brix score and colostrum weight are heritable. We also hypothesized that mode of birth influences early milk composition and changes to composition has secondary effects to calf rumen microbial abundance. Charolaise (CHAR; n = 23) and Angus (ANG; n = 15) dams were divided into two experimental groups; dams underwent vaginal (VD; n= 25) or cesarean (CD; n= 13) delivery. Early milk samples were collected and sent to DHIA to quantify components. After parturition calves were separated based on dam's experimental group. Rumen fluid was collected from calves on d 1, 3, 28 post-partum and DNA extracted from fluid (ANG calves, n=11; CHAR calves, n=13). Results showed that VD significant differences in composition of VD and CD cows. Dams in VD group were more likely to have increased (P  0.05) protein, solids non-fat, and lactose but decreased (P < 0.05) urea concentrations. Similarly, short, medium, and long-chain fatty acids were increased (P  0.05) in VD. Changes in true protein elicited a decrease (P  0.05) in rumen fluid Actinobacteria and Proteobacteria. Results suggest that mode of birth influences protein concentrations in early milk and induces a slight impact on the overall dynamics of the calf rumen microbiome. A second study was conducted to establish relationships between colostrum components, management and calf health as well as determine genetic parameters of colostrum quality traits. Holstein (HO, n= 250) and Jersey (JE, n=289) cow test-day data was obtained from the Animal Genomic and Improvement laboratory server at the USDA. Brix score, colostrum weight, dam age, parity, and 3-month season of calving were also recorded. Colostrum samples from JE cows were sent to DHIA where compositional measurements were obtained (i.e. true protein, fat, lactose, SCS, solid non-fats). Lactoferrin concentration for JE cow colostrum samples was also determined via ELISA. Calf blood samples were collected within 72 h post-partum and TSP quantified. Farm staff recorded colostrum source for 1st feeding and colostrum freshness for 1st and feeding. A PROC Mixed was performed to determine impact of test-day milk composition traits on colostrum quality traits by breed, PROC Mixed with LSMEANS was used to determine relationships of environment, colostrum management, and colostrum components with incidence of scours and respiratory disease in calves. A Pearson correlation was used to determine relationships between colostrum components and quality traits Heritability and repeatability's were calculated using BLUPF90 family of programs. A series of bivariate models were used to calculate genetic correlations of Brix score and colostrum weight with test-day compositional traits. Results indicated that colostrum Brix and volume were impacted by season, breed, and the interaction of breed and season. Calf incidence of disease was impacted by colostrum components and total serum protein levels. Results for Pearson correlation indicated strong correlations between true protein and solid non-fats and Brix (r = 0.99; 0.86). Lactoferrin also had moderate negative correlations with volume and lactose (r = -0.35; -0.33). Heritability estimates results for Holstein Brix and colostrum weight were 0.25 and 0.15. Jersey cow heritability estimates were 0.36 and 0.47, respectively. We also observed some significant genetic correlations with Holstein Brix score and test-day milk (-0.23), fat (0.54), and SCS (0.29) having moderate correlations. Holstein colostrum weight had a strong correlation with test-day milk (0.96). Jerseys had strong genetic correlation of Brix score with colostrum weight (-0.98). Results indicated a low to moderately heritability for Brix score and colostrum weight in both breeds making them receptive to genetic selection in order to improve breeding programs. Strong significant relationships were also found between colostrum compositional traits and colostrum quality traits.

Thesis (M. Tech. (Biomedical technology)) - Central University of technology, Free State, 2013
Breastfeeding is a major source of childhood nutrition and protection, but with South Africa having one of the highest HIV prevalence in the world the risk of HIV transmission from mother to infant through breastfeeding becomes a major issue. Infant mortality due to malnutrition and infections is also of great concern. Exclusive breastfeeding and giving antiretroviral drugs to the HIV-infected mother and the HIV-exposed infant is one of the most significant ways to improve infant survival rates and reduce transmission of HIV through breastfeeding. Whether HIV disease progression and its metabolic impact on the mother will affect the nutrient composition of breast milk is a question that arises. The aim of this study was to determine the possible association between the stage of HIV disease, as measured by the immunological markers, and the nutrient composition of breast milk. The study population consisted of 60 HIV infected female volunteers who were divided into two groups. Milk and blood samples were obtained from 30 HIV-positive women that was not on any ARV treatment and from 30 HIV-positive women that was on ARV treatment. Their HIV status and treatment regime were obtained from their files. Participants were also asked to complete a questionnaire. Macro-nutrients that were measured included lactose, proteins, fat, total solids and the energy content of the breast milk. This was done on the MIRIS Human milk analyser. The micro-nutrients that were measured were calcium and phosphate on the DXC 800 chemistry analyser. Blood analysis was included to determine the stage of HIV disease progression in the HIV-positive mothers and comprised of a CD4/CD8+ T cell count, viral load and a full blood count. CD4/CD8+ T cells were determined using flowcytometry on the BD FACScalibur. The COBAS AmpliPrep/COBAS TaqMan HIV-1 Test was used for the determination of the viral load and the full blood count was done using a Sysmex XT2000i haematology analyser. When comparing the analysed haematological variables, the white blood cells and red blood cells indicated a significant difference between the two groups. Both of the groups were anaemic. The CD3+ T cell count was higher and the CD4+ T cell count was lower than the reference range in both groups. The median CD4+ T cells and HIV-1 viral load for the HIV with treatment group was higher than the HIV-infected without treatment group. The analyzed milk data yielded no p-value of great significance, suggesting that there was no statistically significant difference recorded of the measured nutrients between mothers receiving treatment and those who did not receive any treatment for HIV. The Spearman Correlation Coefficient was used to determine if HIV disease progression would have an influence on the nutrients that were measured. For the HIV-infected without treatment group, a significant correlation was found between the HIV-1 viral load and percentage total solids in breast milk. For the HIV-infected with treatment group the only positive correlation was between the CD4+ T cell count and the percentage total solids and energy content of the breast milk. No strong positive correlation could be established between the immunological markers of HIV disease progression and the analysed nutrients in the breast milk. Taking this into consideration, HIV-positive mothers can breastfeed their babies even if their HIV status is at a more advance phase, but the emphasis should be placed on exclusive breastfeeding and getting the needed support to breastfeed.

Mature human milk composition was determined from monthly samples collected from five, healthy, Caucasian, lactating women. A 72-hour dietary record was kept monthly from the twelfth week of pregnancy to the sixth month postpartum. Nutrient content of milk samples was similar to values reported in the literature. Calcium and zinc concentrations of human milk decreased significantly during the five month study. Moisture, energy, total lipids, protein, and magnesium levels remained fairly constant over the course of lactation. Dietary intake during pregnancy was not significantly correlated with nutrient concentration in human milk. For dietary intake during lactation, a significant correlation was observed between caloric intake and energy content of human milk for the second month of lactation. A significant correlation was observed between protein intake and protein content in the milk for the sixth month of lactation. Zinc concentration was significantly correlated with dietary intake during the fourth month of lactation. No other significant correlation was observed between nutrient content of human milk and dietary intake during the lactation period.
M.S.

The chemical composition of milk (specifically casein, fat, and calcium) is known to affect the quality and functional properties of Mozzarella cheese. Therefore, concentrations of total nitrogen, casein nitrogen, non-casein nitrogen, non-protein nitrogen, true nitrogen, casein nitrogen to total nitrogen ratio, casein nitrogen to true nitrogen ratio, fat, total calcium, total solids, somatic cells, and pH were measured in silo milk samples collected weekly over 18-months from a large dairy plant in Central Valley, California from July 2008 to December 2009 to verify changes and correlate to low moisture part skim Mozzarella (LMPS) characteristics. LMPS mozzarella cheese from the same plant was also collected biweekly during the same period and analyzed five days post manufacture for total nitrogen, water soluble nitrogen, total calcium, water soluble calcium, salt, pH, fat in dry matter and total solids and texture properties (i.e., hardness (g), cohesiveness, springiness, chewiness (g), aggregation index (AGI), and percentage cheese loss during shredding). Significant seasonal variations of total nitrogen, non-protein nitrogen, casein nitrogen, casein nitrogen to total nitrogen ratio, casein nitrogen to true nitrogen ratio, and total calcium in milk were explained using a linear model equivalent to a basic single cosinor model with sine and cosine of week (converted into radians) as predictors. Correlation studies were done between milk composition and cheese composition, milk composition and cheese textural characteristics as well as cheese composition and cheese texture, showing that concentration of total calcium and nitrogen fractions in cheese milk significantly affected the texture and composition of LMPS mozzarella. Also, the cheese total nitrogen, total calcium and water soluble calcium affected the cheese texture. The LMPS Mozzarella that was firmer and more cohesive had less loss during shredding and aggregated to a lesser extent. The milk total nitrogen, non-protein nitrogen, casein nitrogen, casein to total protein ratio, casein to true protein ratio, and total calcium had positive correlation with each other. However, the milk non-casein nitrogen did not significantly correlate with other nitrogen fractions and total calcium of milk. In addition, there was a significant increase of water soluble nitrogen, percent loss in shredding and aggregation index, and a significant decrease of hardness, and chewiness of LMPS Mozzarella ripened at 8.90 C in comparison to the cheese ripened at 3.30 C for 21 days.

Darbo tikslas – nustatyti piene ir jo produktuose esantį riebaluose tirpų vitaminą E ir įvertinti jo dinamiką įtakojančius veiksnius bei jų reikšmingumo lygį. Darbo uždaviniai: 1. Mokslinės literatūros apie riebaluose tirpius vitaminus piene ir jo produktuose analizė ir apibendrinimas. 2. Nustatyti piene ir jo produktuose esantį riebaluose tirpų vitaminą E. 3. Įvertinti veiksnius įtakojančius piene ir jo produktuose esančio riebaluose tirpaus vitamino E dinamiką. 4. Nustatyti piene ir pieno produktuose esančio riebaluose tirpaus vitamino E dinamiką įtakojančių veiksnių reikšmingumo lygį. Tirti iš 3 Lietuvoje esančių pieno ūkių paimti pieno mėginiai ir iš šio pieno pagaminti produktai: pasterizuotas pienas, acidofilinis pienas, raugintas pienas, kefyras, grietinėlė, grietinė, sviestas, išrūgos. Prekybos centre tyrimams įsigyti fermentiniai puskiečiai sūriai ir saldintas sutirštintas pienas. Tyrimai atlikti Lietuvos sveikatos mokslų universiteto Lietuvos veterinarijos akademijos biochemijos katedroje ir maisto tyrimų laboratorijoje. Atliktas tiriamojo pieno cheminės sudėties nustatymas. Vitamino E kiekio piene ir pieno produktuose nustatymas didelės skyros skysčių chromatografijos metodu. Išvados: 1. Atlikus vitamino E kiekio tyrimą iš pieno ūkių paimtuose pieno mėginiuose didžiausią vitamino E kiekį nustatėme Lietuvos žalųjų karvių ūkyje vasarą 0,85 mg/kg, žiemą – 0,80 mg/kg. Mažiausią vitamino E kiekį vasaros piene nustatėme mišriame karvių ūkyje 0,72 mg/kg, žiemos... [toliau žr. visą tekstą]
The aim of the work – determine the milk fat–soluble vitamin E, and evaluate the dynamics influencing factors and their significance levels. Objectives: 1. Analysis and generalization of scientific literature about the fat-soluble vitamins in milk and its products. 2. To detect the fat-soluble vitamin E in milk and milk products. 3. To access the factors influencing the fat-soluble vitamin E dynamics in milk and its products. 4. To determine significance of fat-soluble vitamin E dynamics influencing factors in milk and milk products. Milk samples and dairy products from this milk: pasteurized milk, acidophilic milk, acidified milk, kefir, cream, sour cream, butter, were investigated which have been taken from dairy farms in Lithuania. The research was carried out in the Biochemical department of Lithuanian Health Science University Veterinary Academy and laboratory of food analysis; Lithuanian fermented semi-hard cheese and sweetened condensed milk from trade centers were investigated. The chemical composition of milk has been determinated. Vitamin E content in milk and milk products were determinate by high performance liquid chromatography. Conclusions: 1. During examination of vitamin E content in milk from farms, the highest content of vitamin E was found in the third cows farm: at summer 0,85 mg/kg, at winter 0,80 mg/kg. The lowest content of vitamin E at summer was found in the second farm 0,72 mg/kg and the lowest content of vitamin E at winter was found... [to full text]