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1
Skrypzeck, Heidi. "An assessment of the contributions of Afrikaner, Hereford and Simmentaler in composite breed development in beef cattle". Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51591.
Testo completoAbstract (sommario):
Thesis (MScAgric)--University of Stellenbosch, 2000.ENGLISH ABSTRACT: The objective of this study was to obtain more information regarding the characterisation of Afrikaner (A), Hereford (H) and Simmentaler (S) breeds in an initial crossbreeding programme and subsequent composite development. This involves the estimation of breed additive effects, breed maternal, individual heterotic effects and maternal heterotic effects in the initial crossbreeding phase and the estimation of genetic parameters and prediction of breeding values in later generations for birth weight (BW), weaning weight (WW) and cow efficiency (CE; WW/dam weight" 75 x 100) in an intensive environment under high stocking rates. In the analysis of the initial crossbreeding phase, the S breed direct effects, expressed as deviation from the general mean, were positive (P :s; 0.01) for both BW and WW. Hereford and A breed direct effects were negative (P :s; 0.01) for both BW and WW. Afrikaner direct maternal effects were positive (P :s; 0.01) for both BW and WW. The H direct maternal effect was negative (P :s; 0.05) (- 2.8%) for WW. Simmentaler maternal effect was negative (P :s; 0.01) for BW but non-significant (P ;:::0:.05) for WW. Individual heterotic effects for BW were significant (P:S; 0.01) in H x S (3.5%) and S x A (11.0%) only. Individual heterotic effects were positive (P :s; 0.01) for WW, with that of the H x A (9.8%) and S x A (6.7%) crosses exceeding the H x S (3.1%) cross. Maternal heterotic effects were non-significant (P ;:::0:.05) for both BW and WW. Investigations of the contributions of the A, Hand S during composite development in later generations, respectively, were made to estimate direct heritabilities (h2 a) and maternal heritabilities (h2 m) for BW and WW of the calf and CE of the dam. Calves were born between 1968 and 1993 (n = 52628). Calves of this composite population had varying levels of A, Hand S genes ranging from o to 75%, 0 to 100% and 0 to 96.9%, with an average of 4.3,19.3 and 33.4%, respectively. For the A, direct heritabilities fitting unitrait models were 0.67, 0.53 and 0.19 for BW, WW and CE, respectively, with corresponding estimates of h2mbeing 0.22, 0.36 and 0.58. Genetic correlations between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to - 0.62. Direct breeding values for BW increased and reached a maximum value at 0.11 proportion of A. The maternal breeding values for BW decreased linearly between 1.6 to 37.5% A proportion and increased linearly between 37.5 to 75% A proportion. For WW, the direct breeding values decreased linearly with increasing A proportion, while the maternal breeding values were not affected by proportion of A. Cow efficiency was unaffected by an increase in proportion of A. For the H, direct heritabilities fitting unitrait models were 0.67,0.52 and 0.21 for BW, WW and CE, respectively, with corresponding estimates of h2mbeing 0.22, 0.36 and 0.60. Genetic correlations between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to - 0.64. Direct breeding values and maternal breeding values for BW and WW decreased with increasing proportion of H. Direct breeding value for CE increased, while the maternal breeding value for CE reached minimum value at 0.62 proportion ofH. For the S, direct heritabilities fitting unitrait models were 0.66, 0.53 and 0.21 for BW, WW and CE, respectively, with corresponding estimates of h2m being 0.22, 0.36 and 0.59. Genetic correlations between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to - 0.63. Direct breeding values for BW and WW decreased and maternal breeding values increased with increasing proportion of S. Cow efficiency was unaffected by an increase in proportion of S. The study suggests that in the initial crossbreeding phase, purebred S breeding seems to be the best breeding practice for this environment and that during composite development, high A and H contributions could lead to low BW and WW (except the maternal contribution of the A for BW and WW). The advantage of the S lies more in the maternal contribution than in the direct contribution suggesting that the S is a large-framed maternal line rather than a terminal sire line.
AFRIKAANSE OPSOMMING: 'N WAARDEBEP ALING VAN DIE BYDRAE VAN DIE AFRIKANER, SIMMENTALER EN HEREFORD TYDENS KOMPOSIETE RASONTWIKKELING BY VLEISBEESTE: Die doel van die studie was om inligting aangaande die karakterisering van die Afrikaner (A), Hereford (H) en Simmentaler (S) rasse tydens die oorspronklike aanvangsfase van kruisteling en daaropvolgende komposiet ontwikkeling te verkry. Dit het die beraming van direkte additiewe, individuele heterose, direkte materne en materne heterotiese effekte tydens die aanvangsfase van die kruisteeltprogram, die beraming van genetiese parameters en die voorspelling van die teeltwaardes in latere generasies behels. Die eienskappe wat ingesluit is, is geboortegewig (BW), speengewig (WW) en koeidoeltreffendheid (CE; WW/koeigewigo.75 ). Hierdie kudde is in 'n intensiewe maar onder 'n hoë weidingsdruk omgewing aangehou. Tydens die ontleding van die eerste kruisteeltfase is die direkte additiewe effekte vir die S, uitgedruk as afwyking van die algemene gemiddelde, vir beide BW en WW positief (P ~ 0.01). Direkte additiewe effekte vir die H en A was vir beide BW en WW negatief (P ~ 0.01). Afrikaner materne effekte was vir beide BW en WW (P ~ 0.01) positief. Die H direkte materne effekte was negatief (-2.8%) (P ~ 0.05) vir WW. Simmentaler maternal effekte was ook vir BW negatief (P ~ 0.01), maar nie-betekenisvol (P 20.05) vir WW. Individuele heterose was slegs betekenisvol (P ~ 0.01) vir kombinasies van H x S (3.5%) en S x H (11.0%) vir BW. Individuele heterose was positief (P ~ 0.01) vir WW waar H x A (9.8%) en S x A (6.7%) kruisings dié van die H x S (3.1%) kruising oortrefhet. Materne heterose was vir beide BW en WW nie-betekenisvol (P 2 0.05). Die relatiewe bydraes van die A, H en S is ook tydens komposiet-ontwikkeling bereken. Direkte additiewe oorerflikhede (h2 a) en materne oorerflikhede (h2m) is vir BW en WW van die kalf en CE van die koei beraam. Kalwers in die komposiet kudde, gebore tussen 1968 en 1993 (n = 52628), het variërende vlakke van A, H en S gene. Die samestelling het gevarieer van 0 - 75%, 0 - 100% en 0 - 96.9%, met 'n gemiddeld van 4.3, 19.3 en 33.4%. Vir die A was die direkte erfbaarhede (h2 a), soos deur die passing van 'n enkeleienskapmodel beraam, 0.67, 0.53 en 0.19 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings van 0.22, 0.36 en 0.58 vir h2 rn- Genetiese korrelasies tussen direkte en mateme effekte (ram)was almal negatief en het tussen -0.32 en -0.62 gewissel. Direkte teelwaardes vir BW het met toenemende A-bydrae gestyg en het 'n maksimum waarde by 0.11 bereik. Die mateme teelwaardes vir BW het lineêr gedaal tussen 1.6 en 37.5% A-bydrae en het weer lineêr tussen 37.5 en 75% Abydrae gestyg. Vir WW het die direkte teelwaardes lineêr met toenemende A-bydrae gestyg, terwyl die mateme teelwaardes nie deur A-bydrae beïnvloed was nie. Koeidoeltreffendheid was nie deur 'n toename in A-bydrae beïnvloed nie. Vir die H was die direkte erfbaarhede (h2 a), soos deur die passing van 'n enkeleienskapmodel beraam 0.67, 0.52 en 0.21 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings van 0.22, 0.36 en 0.60 vir h2 rn- Genetiese korrelasies tussen direkte en mateme effekte (ram)was almal negatief en het tussen -0.32 en -0.64 gewissel. Direkte teelwaardes en mateme teelwaardes vir BW en WW het met toenemende H-bydrae gedaal. Direkte teelwaarde vir CE het ook met toenemende If-bydrae gedaal, terwyl die mateme teelwaarde 'n minimum waarde by 0.62 H-bydrae bereik het. Vir die S was die direkte erfbaarhede (h2a), soos deur die passing van 'n enkeleienskapmodel beraam 0.66, 0.53 en 0.21 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings van 0.22, 0.36 en 0.59 vir h2 m- Genetiese korrelasies tussen direkte en mateme effekte (ram)was almal negatief en het tussen -0.32 en -0.63 gewissel. Direkte teelwaardes vir BW en WW het gedaal, terwyl die mateme teelwaardes met toenemende S-bydrae gestyg het. Koeidoeltreffendheid was nie deur 'n toename in S-bydrae beïnvloed nie. Die bevinding was dat tydens die ontleding van die eerste kruisteeltfase die teling van suiwer S aanbeveel word en dat tydens komposiete-ontwikkeling toenemende A- en H-bydraes neig om aanleiding te gee tot afnames in BW en WW (behalwe die mateme bydrae van die A vir BW en WW). Die S-bydrae se voordeel is meer in die mateme bydrae as in die direkte bydrae geleë en dui dus aan dat die S as 'n mateme grootraam lyn i.p.v. as 'n terminale bullyn gebruik moet word.
2
Matjuda, Lehotlo Ephraim. "Development breeding objectives for the nguni cattle breed in South Africa". Thesis, University of Limpopo (Turfloop Campus), 2012. http://hdl.handle.net/10386/862.
Testo completo
3
Afolayan, Raphael Abiodun. "Genetics of growth and development in cattle". Title page, table of contents and abstract only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09pha2579.pdf.
Testo completo
4
Mazhar, Kehkashan. "Molecular genetic markers for selection and genome mapping in cattle". Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260797.
Testo completo
5
Meacham, Nancy S. "Heritability estimates for calving date in Simmental cattle". Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45782.
Testo completoAbstract (sommario):
Variation among sires in daughters' reproductive performance was analyzed using data on 4,360 cows from nine herds obtained from the American Simmental Association. Cows were required to have at least 50% Simmental breeding, to have calved first at 2 yr of age and to have been born and subsequently calved in the same herd and season. Traits analyzed included first and second calving dates, first calving interval and the percentage of cows that returned to calve in the same season as 3-yr-olds. Data were adjusted for effects of percentage Simmental and first-calf calving ease score.
At second calving, purebred Simmentals calved 1.7 ± 1.2 d later than 75% Simmental cattle and 5.1 ± 1.4 d later than 50% Simmental cattle. When compared to cows that calved without assistance at first calving, cows experiencing easy pulls were 1.7 ± 1.4% less likely to calve as 3-yr-olds and had 4.9 ± 1.0 d longer calving intervals. Cows with hard pulls were 9.0 ± 2.1% less likely to return and had 6.5 ± 1.6 d longer calving intervals. Cows requiring Cesarean section were 23.1± 2.5% less likely to return and had 19.6 ± 2.4 d longer calving intervals. Heritability estimates were .17 ± .04 for first calving date, .07 ± .06 for second calving date, .04:105 for calving interval and .11 ± .04 for percent return. Calving interval does not appear to be a useful selection criterion to improve reproduction. Phenotypic and genetic correlations of first calving date with calving interval were -.58 and -.83 ± .37, respectively. The genetic correlation between first and second calving dates was .66 ± .41. Given current data recording procedures, calving date appears to be the most useful potential selection criterion to improve reproductive fitness.Master of Science
6
Brown, Timothy P. (Timothy Phillip). "Selection indices in retrospect for dairy cattle". Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59266.
Testo completoAbstract (sommario):
Selection differentials and selection indices in retrospect were calculated to determine the relative emphasis placed on production and type traits through bull selection. Indices in retrospect including only production traits indicated that, for Holsteins, fat yield was the trait most heavily selected for between 1978 and 1987, followed by protein percent and then milk yield. Fat percent and protein yield had negative index weights throughout the nine year period. In Ayrshires, similar weights were observed except that milk yield index weights were negative throughout the nine year period. It was found that the relative weight placed on type was small and did not affect the relative weights place on production traits. Within Holsteins, differences in bull selection when multiple services were required to successfully service a cow indicated that selection for overall size was reduced in later services. Within Ayrshires, there were no differences in any production or type trait within multiple services.
7
Green, Ronald T. "Evaluation of optimum and near optimum pair selection methods for increasing predicted relative net income in Jersey cattle". Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45650.
Testo completoAbstract (sommario):
To evaluate the importance of non-linear relationships between Relative net income per day of productive life (RNI/DPL) and individual traits, 921,915 potential offspring were simulated from all possible matings of 20,487 Jersey cows and 45 active AI sires. Predicted milk yield, fat yield, and 13 linear type traits of potential progeny were used to predict RNI/DPL of all potential progeny.
Five methods of mate selection and pairing were evaluated for their effectiveness in choosing mates and the amount of computer time required to choose those pairings. Results of a linear programming (LP) method were used as a comparison for the other four more easily applied methods. Two of the other four methods were not significantly (P > .01) different from the LP method. Although the random pairing method was significantly different, similarity of results, for this method indicated non-linear relationships between RNI/DPL and individual trait scores are of minor importance. A11 four methods used considerable less computer time than the LP method.
Analysis of variance for predicted RNI/DPL (all possible offspring) indicated herd, dam within herd, sire, and inbreeding class to be significant (P < .01) variables in determining RNI/DPL. However the sire by dam within herd interaction did not significantly affect RNI/DPL, again indicating non-linear relationships between traits and RNI/DPL were not very important.
Regressing PDâ s, Clâ s, and their crossproducts for milk yield, fat yield, and 13 linear type traits showed the relative importance of crossproducts to be minimal in comparison to the linear ellects of parental genetic evaluations.
Master of Science
8
Mitchell, Jay Douglas. "An Economic Assessment of Genetic Information: Leptin Genotyping of Breeding Cattle". Thesis, North Dakota State University, 2006. https://hdl.handle.net/10365/29904.
Testo completoAbstract (sommario):
Recent studies show polymorphisms in the leptin gene significantly impact milk production in dairy cattle. If the leptin gene were to have a similar impact on beef cattle, calf weaning weights would be expected to increase from the increased milk production in the cows. Since weaning weight is a key component of profitability in a cow-calf operation, leptin genotyping may prove to have an economic impact in breeding cattle. However, no research has been done to link the economic impact of increased milk production to breeding cattle. Using 595 observations from genotyped cows spanning 11 years (1995-2005), calf weaning weight by genotype is estimated as a function of calf and dam characteristics and environmental effects. A MIXED procedure, utilizing data from 89 culled cows, is used to determine statistical differences in average cull age by genotype. A simulation model calculates mean annualized equivalent return by genotype and breed using the regression coefficients and residuals and 16 years of price data.
results show that at least one T-allele in breeding cows increases calf weaning weight, average cull age, and annualized equivalent return compared to cows with homozygous C-alleles. These results indicate that there may be future premiums and discounts for breeding cattle based on genotype. Seedstock producers could potentially begin to segregate herds based upon genotype so that they could sell genotypic registered products. Cow-calf producers may also benefit from this knowledge by increasing the
amount of TT genotype breeding cattle in their herd to maximize profits.
9
Botha, Theunis Christoffel. "Effect of selected physical and production traits on the tick burdens of beef cattle". Thesis, Port Elizabeth Technikon, 2002. http://hdl.handle.net/10948/91.
Testo completoAbstract (sommario):
The objective of this study was to determine the effect of selected traits such as age, sex, body weight, body length and height, body condition score (BCS), coatscore (CS), skin thickness and average skin surface temperature on tick burdens in beef cattle. Bonsmara cattle (n= 143) were used to measure visible tick counts, body condition score, coat score, skin thickness, body height and length, body weight, body surface temperature, gender and inter calving period. Measurements were taken from April to December. All animals were managed extensively on natural and cultivated pastures near George in the Southern Cape. Female animals had significantly (p<0.05) greater tick infestation (37.98±2.7) compared to male animals (16.52±1.2). Age was a significant factor (p<0.001) with the younger animals below two years having (46.40±5.26) more ticks than those of two years and older (20.15±2.44). A significant negative correlation (p<0.001; -0.29) was reported between the infestation of ticks on the animals and the age of the animal. Animals with an average body weight below 250kg had 42% (p<0.05) more ticks compared to animals with a body weight above 250kg. Age of the animal and weight were highly correlated (r= 0.70); p<0.001), while the correlation between the number of ticks per cow and the mean weight was negatively correlated (r= -0.37; p<0.001). Skin surface temperature significantly influenced tick infestation on the animals (p<0.001). The degree of infestation increased as body surface temperature exceeded 30º C. Coat score, skin thickness, body condition score and inter calving period did not significantly influence tick infestation on the animals. The infestation of ticks on the animals were significantly influenced by body height (p<0.019) and body length (p<0.001). Animals smaller than a 130cm in height had a significantly (p<0.05) greater tick infestation (36.5±5) compared to animals taller than 130cm (21.2±1.5). This trend was also observed for body length. Animals with a body length shorter than 145cm had a greater (p<0.05) average tick infestation of 41.3±4.5 compared to 23.2±1.3 to animals longer than 145cm, indicating a 44% greater tick infestation in favour of the shorter animals. For increased production and tick resistance animals should have smoother coats and be able to dissipate heat effectively.
10
Gotschi, Manuela. "The use of blood metabolic concentrations as indicators of the metabolic and productive status in dairy cows". Diss., Pretoria : [s.n.], 2000. http://upetd.up.ac.za/thesis/available/etd-01312008-145827.
Testo completo
11
Hossain, Khandaker Bayazid. "STATISTICAL GENETIC STUDY ON CATTLE BREEDING FOR DAIRY PRODUCTIVITY IN BANGLADESH". Kyoto University, 2000. http://hdl.handle.net/2433/151599.
Testo completoAbstract (sommario):
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第8568号
農博第1151号
新制||農||810(附属図書館)
学位論文||H12||N3447(農学部図書室)
UT51-2000-M32
京都大学大学院農学研究科応用生物科学専攻
(主査)教授 佐々木 義之, 教授 守屋 和幸, 教授 矢野 秀雄
学位規則第4条第1項該当
12
Perotto, Daniel. "Additive and nonadditive genetic effects on growth and milk production traits in Holstein Ayrshire crossbreeding experimental data". Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70266.
Testo completoAbstract (sommario):
Crossbreeding parameters (additive (a), dominance (d) and additive x additive (aa) epistatic effects for individual $ sp{ rm (I)}$ and for maternal $ sp{ rm (M)}$ performance) on body weight growth and first lactation performance traits of females from a crossbreeding experiment between Holstein (H) and Ayrshire (A) based lines were estimated by individual animal models, incorporating all known additive genetic relationships amongst animals, through restricted maximum likelihood and mixed-model methodologies.The growth traits (asymptotic weight (A), rate parameter (k), inflection parameter (m), average lifetime absolute growth rate (AGR), average lifetime absolute maturing rate (AMR) and average lifetime relative growth rate (RGR)) were estimated by fitting the nonlinear equation, W$ sb1$ = A(1 $ pm$ be$ sp{ rm -kt}) sp{ rm M}$, to the observed weight-age data of 3076 individual females.
Results from the analyses of growth traits indicated that the H line exceeded the A line in addition genetic effects for individual performance (a$ sp{ rm I}$) for both A and AGR. The H line also exceeded the A line in additive effects for maternal performance (a$ sp{ rm M}$) in trait A. Both dominance (d) and additive x additive (aa) epistatic effects were statistically important in most cases. Individual heterosis (h$ sp{ rm I}$ = d$ sp{ rm I}$ $-$ 0.5aa$ sp{ rm I}$) was positive for traits A and AGR, whereas maternal heterosis (h$ sp{ rm M}$ = d$ sp{ rm M}$ $-$ 0.5aa$ sp{ rm M}$) was negative for A and positive for AMR. Total heterosis (TH = h$ sp{ rm I}$ + h$ sp{ rm M}$) had positive effects on AGR and AMR. For all growth traits, heterosis retained in advanced crossbred generations was statistically irrelevant. The overall conclusion was that crossbreeding systems designed to capitalize on TH would produce faster growing and earlier maturing animals.
The analyses of production traits found the additive effect of the H line for individual performance to be a major factor to increase yields of milk, protein and fat. On the other hand, line maternal and cytoplasmic source tended to favour the A line, but none reached statistical significance in any of the traits. Results indicate that two-line specific crosses or synthetic development would be sound breeding strategies for taking advantage of first cross heterosis or of line additive differences, respectively.
Estimates of crossbreeding parameters from mixed-model analyses, were found to be more reliable than those from ordinary least squares analyses. (Abstract shortened by UMI.)
13
Sinclair, Kevin D. "Metabolism in cattle and regulation of anterior pituitary hormone release". Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU079035.
Testo completoAbstract (sommario):
Experiments were designed to assess the effects of energy and protein intake on metabolic function and reproductive efficiency in single and twin suckling beef cows and heifers. A role was proposed for endogenous opioid peptides in mediating the effects of photoperiod, suckling and nutrition on anterior pituitary hormone release, and tested with respect to nutrition. The first two experiments were designed to quantify the effects of pre- and post-partum energy and protein intake, on milk yield and composition, body tissue mobilisation, the post-partum anoestrous interval, and subsequent conception rates to artificial insemination and embryo transfer in single- and twin-suckling beef cows. Cows very quickly adjusted their metabolism and level of performance to be in line with their current level of energy and protein intake. Ovulation and the resumption of normal oestrous cycles occurred soon thereafter. The third experiment tested the hypothesis that post-partum energy and digestible undegradable protein (DUP) intake can influence hypothalamic opiodergic tone and the ability of the anterior pituitary to secrete luteinizing hormone (LH), prolactin and growth hormone in response to naloxone (an opioid receptor antagonist) challenge. Results indicated that high energy diets allowed cows to overcome the opioid mediated block on LH release and resume oestrous cyclicity earlier than cows on low energy diets. High levels of DUP increased the opioid mediated block on LH release. The final experiment examined the interactive effects of body condition and energy intake on hypothalamic opioidergic tone and pituitary responsiveness, in terms of LH release, when challenged with an exogenous source of gonadotrophin-releasing hormone (GnRH). Naloxone was unable to evoke consistent LH responses in this experiment but the LH response to GnRH was influenced by both body condition and energy intake. In conclusion opioid peptides may provide a means by which certain homeostatic regulators interface with homeorhetic hormones released from the anterior pituitary gland.
14
Ulutas, Zafer. "Production traits and market values of Welsh black cattle". Thesis, Bangor University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262765.
Testo completo
15
Diaz-Martin, Clara. "Correlation of predicted breeding values across environments in the presence of selection for direct and maternal breeding values". Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/39438.
Testo completoAbstract (sommario):
A simulation approach was used to determine the effects of multitrait selection on the correlations of sire direct and maternal predicted breeding values across environments. True and predicted direct and maternal breeding values (BV) of sires were simulated for sires evaluated independently in two different environments. Prediction error variances and covariances among direct and maternal BV within environments were required for the simulation. To obtain the necessary input parameters, a variety of MME coefficient matrices were created and inverted to inspect relationship among accuracies and correlations of prediction errors in sire evaluation models. An empirical prediction equation to predict the necessary prediction error covariances was obtained. Divergent, directional and random multitrait selection was then practiced using direct and maternal predicted BV as selection criteria. Samples of 40 sires were randomly obtained from each selected population. Observed correlations between direct and maternal predicted BV across environments were compared to expectations derived from univariate distribution theory. Selection definitely affected the expectations. However, the adjustment developed from univariate theory appeared to accommodate the effect of selection in these expectations.Ph. D.
16
Todd, Darren Lindsay. "Implementation of genomic selection in UK beef and sheep breeding". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8766.
Testo completoAbstract (sommario):
Genomic selection (GS) has been adopted by the dairy cattle breeding industry and the opportunity exists to implement this technology in UK beef and sheep breeding. However, these sectors do not appear so readily predisposed to GS implementation. Following an introduction to GS in Chapter 1, Chapter 2 investigated the structure of the little-studied UK beef breeding sector. This provided estimates of key commercial and pedigree population parameters, for use in modelling genetic gain from GS. Terminal traits were found to be the dominant selection goals, with 85% of beef-sired commercial matings resulting in progeny being slaughtered at a prime age. Pedigree bulls disseminated the majority of genes in the sector via natural service. The correlation between the terminal selection index (TI) and the sale price of breeding bulls was moderate, suggesting a modest uptake of genetic technology in the sector. Chapter 3 estimated selection intensity for TI, generation interval and the dissemination rate of improved genes in the pedigree Limousin population. In order to predict the genetic gain achievable in using GS in beef and sheep breeding, Chapters 4 to 6 undertook deterministic selection index simulations, incorporating genomic information as correlated traits. In Chapter 4, GS was modelled for terminal beef traits, when incorporating carcass information and accounting for likely genotype by environment interaction. Using a training population of 2000 sires, this concept was predicted to offer 40% greater genetic gain than existing BLUP selection using pedigree phenotypes. Gene flow methodology projected the commercial value of this gain to offer a substantial return net of genotyping costs. Chapter 5 explored GS for maternal beef traits within the concept of a nucleus breeding scheme. Whilst greater genetic gain was predicted with GS than with conventional BLUP, the economic value of this gain was projected to be too low to justify such a scheme in the UK. Chapter 6 proposed a synergy between computer tomography (CT) phenotypes and GS in sheep breeding. Developing a genomic predictor from male selection candidates with CT phenotypes and conventional performance records was predicted to increase genetic gain by 55% over BLUP selection without CT traits. Introducing GBV contributed most of the accuracy in this scenario, suggesting that the existing performance recording structure in UK sheep breeding could in the future be replaced by GS using CT. In the general discussion, the potential for GS in other beef and sheep traits was considered in the light of the outcomes of these simulations. Given the lack of vertical integration in UK beef and sheep sectors, the drivers for implementation of GS are examined. Finally, the options for international cooperation and the possibilities offered by future genotyping technology are considered. It was concluded that implementation of GS incorporating beef carcass phenotypes was merited and could provide a platform for future GS implementation in other novel traits. Sheep GS with CT traits was considered a higher risk strategy, due to the lack of evidence for uptake of existing EBV technology.
17
Tosi, Hugo Ricardo. "Dairy cattle breeding performance when grazing the high protein pastures of Uruguay". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ35047.pdf.
Testo completo
18
Shadwick, Mark. "An investigation of the MLC beef bull index". Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386691.
Testo completo
19
Persson, Ylva. "Breeding soundness evaluation of young beef bulls /". Uppsala : Dept. of Clinical Sciences, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200718.pdf.
Testo completo
20
Hird, Wendy Louise. "The effect of milk pricing on genetic selection goals in British Columbia and Quebec dairy cattle populations". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24683.
Testo completoAbstract (sommario):
This study has compared the effect of milk pricing systems on the selection goals of dairy producers in two provinces of Canada, British Columbia (BC), and Quebec. These provinces were chosen for comparison as BC produces milk largely for a fluid market, while Quebec produces milk for a manufacturing market. Within BC, due to a higher utilization and higher milk price, the value/kg of skim on Vancouver Island was higher than that of the Vancouver Lower Mainland over the study period 1963-1982. Between the two provinces, the value/kg of skim in BC was found to be consistently higher than in Quebec over the 20 year period, while the value of fat was higher in Quebec than BC. In BC in 1980, the value of a kilogram of skim was approximately $0.30, whereas its value in Quebec was only $0.20. During the 1960s in BC, the value of skim represented one half the value of milk, and in 1982 it comprised two thirds of the value of milk, as compared to Quebec, where fat represented 43% of the value of milk. Net economic values were calculated by subtracting the dollar cost of production associated with the components of milk (carrier, fat and protein), from the gross value/kg of skim and fat. These values showed that the value/kg of protein was negative and decreasing in both BC and Quebec. The economic value/kg of butterfat has been consistently positive and increasing over the study period in BC and Quebec to $3.27 and $3.34/kg respectively in 1982. The relative economic values of carrier, fat and protein in BC and Quebec in 1982 were 0.08:1.00:-0.10 and 0.06:1.00:-0.12 respectively, which puts moderate selection on carrier and fat, and negative selection on protein. Selection index weights for carrier, fat and protein revealed that the BC dairy industry has always applied positive selection to the carrier and fat portion, and negative selection to the protein portion of milk. In 1982 the selection weights were 0.087:1.253:-1.189. The Quebec index has shown more fluctuation that BC, with less selection against solids compared to BC; (0.050:1.280:-0.657). Theoretical genetic goals of the BC dairy industry have been consistent at approximately 3.0% butterfat, 2.0% protein and 95.0% carrier. The genetic goals in Quebec have undergone wide fluctuations, but generally have signalled the dairy producer to increase both butterfat and protein. The goals of the two industries are now very similar, with the exception that Quebec continues to place higher value on solids than BC.Land and Food Systems, Faculty of
Graduate
21
Nugent, Russell Arthur. "Analysis of newborn calf body measurements and relationship of calf shape to sire breeding values for birth weight and calving ease". Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07282008-135956/.
Testo completo
22
Skinner, John. "A dairy cattle breeding and management computer simulation program for teaching and research". Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26076.
Testo completoAbstract (sommario):
The increased power and availability of computers has resulted in an increase in the value of simulation as a means of furthering our understanding of systems. Reducing the components and interactions of a system to mathematical models enables simulation to provide a clear basis of the system and this can be useful for teaching and research. Simulation is especially suited for studying genetic gain in dairy cattle because there are already reliable mathematical models available. Analyzing genetic gain in practice is difficult due to the numerous and diverse factors that affect it.
This project has provided a computer program that simulates the inheritance of the economically important traits in dairy cattle and includes interactions with the biological, management and economic factors which can affect genetic gain. It was designed primarily as a teaching tool for senior undergraduate students in animal genetics or dairy science, to heighten students interest and encourage them to think more deeply about the subject. Features were also included to make the simulation useful in research for stimulating and refining research objectives and for analyzing questions not easily tested in the field.
The program models the system at the cow level with critical management decisions made on a continuous basis and summaries and other management decisions on a calendar year basis. Mature equivalent milk production is given in Breed Class Averages and the quota system of limiting milk production is used so that any small Canadian dairy population can be simulated. Parameters are provided and documented for simulating a Fraser Valley population.
Since a dairy population is an extremely complex system improvements and expansions to this simulation can be made. While some expansions and improvements are possible with existing information many would require more research to provide parameters and bases for models. Use and testing should reveal the changes that are the most beneficial and feasible.
The program has been written in a modularized form to more easily facilitate changes and additions. Full instructions, sample runs and documentation have been included to encourage knowledgeable use and expansion of the program.Land and Food Systems, Faculty of
Graduate
23
Stella, Alessandra. "Strategies for applying marker assisted selection in nucleus breeding schemes in dairy cattle". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ56295.pdf.
Testo completo
24
Holgate, Katheryn T., e University of Lethbridge Faculty of Arts and Science. "The effects of cattle grazing on the breeding biology of riparian forest birds". Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 1999, 1999. http://hdl.handle.net/10133/349.
Testo completoAbstract (sommario):
Cattle grazing in riparian zones can have large impacts on vegetation characteristics and avian biodiversity. To assess these impacts in southern Alberta, vegetation and bird surveys were conducted in twelve riparian sites (four each in heavily grazed, moderately grazed, and ungrazed habitats) along the Oldman River. The shrub understory and bird species diversity and abundance declined significantly as grazing intensity increased. Settlement patterns, territory sizes, and food provisioning rates of some bird species were examined to assess the mechanisms behind this reduction. Five out of seven species settled earlier in ungrazed habitats, whereas two species did not show any discernable settlement pattern. The territory sizes of three species examined increased as grazing intensity increased. House wrens (Troglodytes aedon) brought more food and more food biomass to their nests in ungrazed habitats. These results indicate that available food biomass decreased as grazing intensity increased, and is an important factor in population dynamics of some species.29 cm.
25
Krebs, Elizabeth Ann. "Reproduction in the cattle egret (Bubulcus ibis ibis) : the function of breeding plumes". Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60507.
Testo completoAbstract (sommario):
This study investigates the colonization of Barbados, the seasonality of breeding, and the function of breeding plumes in the cattle egret Bubulcus ibis ibis. Colonization occurred around 1956, and the island now has 4 colonies. Numbers of birds at each colony are still increasing. Colonies are evenly spaced around the island. Plumage scores varied seasonally, and males had higher scores than females. Breeding activity peaked in July-August and November-March. Conspecific interference may force poorly plumed birds to breed when environmental conditions are poor. Chick mortality was primarily from starvation during periods of low breeding activity, and primarily from conspecific attack during high breeding activity. Fledging success did not increase with breeding activity. Plumage scores correlated positively in breeding pairs. Well-plumed males fed chicks more often than poorly plumed males and had the higher fledging success. Males contributed more to nest and nestling attendance when their mates were well plumed. Plumes appear to indicate the potential paternal care and the genetic quality of a mate.
26
Mrode, Raphael Aweyevu. "Genetic response to selection for rate and efficiency of lean gain in beef cattle". Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/15445.
Testo completo
27
Mogale, Moneri Sanah. "The use of indigenous knowledge in beef cattle husbandry in Tshebela Village, Limpopo Province". Thesis, University of Limpopo, 2017. http://hdl.handle.net/10386/1959.
Testo completoAbstract (sommario):
Thesis (M. Dev.) -- University of Limpopo, 2017There is a gap in the literature about the role and relevance of Indigenous Knowledge and beef cattle welfare in many parts of the Limpopo province. This gap is relevant because many marginalised cattle owners use indigenous knowledge in their day to day management of beef cattle. The aim of the study is to investigate the use of IK methods on beef cattle husbandry in Tshebela village in the Capricorn district of the Limpopo province as a contribution to filling the void identified above. The objectives of the study were as follows: -To investigate the IK methods used in beef cattle husbandry in the area of the study; -To assess if beef farmers use IK to identify medicinal plants to cure beef cattle; -To investigate farmers‘ perceptions and attitudes on the use of IKS on beef cattle husbandry in the area of study. A qualitative methodology that was used was primarily phenomenological in design. A purposive sampling technique was used and twenty seven (27) traditional beef farmers, two (2) local herbalists were recruited as participants. Data was collected through focus group discussions, key informant interviews, and observations. An interpretative phenomenological-based analysis was used to surface the role and relevance of indigenous knowledge in beef cattle husbandry. The findings suggest that indigenous knowledge is used by cattle owners alongside modern knowledge and that communal farming posed some challenges to the farmers.
28
Sianangama, Pharaoh Collins. "Effects of human chorionic gonadotropin administration at various times following breeding on corpus luteum number, diameter, progesterone profiles and pregnancy rates in dairy cattle". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28745.
Testo completoAbstract (sommario):
Corpus luteum (CL) dysfunction has been implicated among various factors predisposing early embryonic mortality in cattle. Two experiments were conducted to evaluate the efficacy of using human chorionic gonadotropin (hCG) given either at the time of breeding (day 0) , day 7 or 14 post breeding, in reducing that component of early embryonic mortality caused by CL dysfunction. The aims of experiment 1 were to investigate the effectiveness of using hCG, in inducing the development of accessory CL, their formation and growth, and the effect of such treatments on the function of both the induced and spontaneous CL.
Thirty-four lactating Holstein cows were randomly assigned to one of four treatments. A single intramuscular injection of 1000 IU of hCG was given either at the time of breeding (day 0, n=8), day 7 (n=9) or 14 (n=9) post breeding or no hCG given (control, n=8). A real-time ultrasound machine was used to study follicular dynamics and CL growth. The CL and antral follicle diameter was determined using a built-in system of calibrated callipers. Ultrasound scanning was carried out on days 7, 9, 11, 14, 16, 18, 21, 28, 35 and 42 post breeding. Blood and milk samples, for progesterone (P₄) determination using radioimmunoassay, were collected on days coincident with ultrasonography. Diameter of the CL is presented as the sum of the diameter of all luteal tissue in each animal. Differences in CL diameter, milk and plasma P₄ were analyzed using the General Linear Models Procedures while pregnancy data were analyzed using Chi-Square analysis in Statistical Analysis Systems (SAS, version 6.3).
Based on the day 7 ultrasound scanning, the incidence of twin ovulations was higher among cows treated on day 0 (3/8) compared to control cows (1/8) and day 7 (1/9). Accessory CL were detected in 7/9 of the day 7-treated cows compared to 4/9 among the day-14 treated cows. Least squares means (LSMeans) for CL diameter were significantly higher (P<0.001) among cows treated with hCG compared to control cows starting at day 7 continually until day 42. Plasma P₄ profiles were significantly higher (P<0.05), at days 18, 35 and 42, in cows treated on day 7 or 14 compared to control cows. The first detectable differences (P<0.05) between hCG treated and control cows, in milk P₄ occurred at day 21 and persisted until day 42. Pregnancy rates were highest among cows treated with hCG on day 7 where 6 of the 9 cows were diagnosed pregnant. Corresponding pregnancy rates for day 0, 14 or control cows, were 4/8, 5/9 and 3/8, respectively.
In the second experiment, two trials were conducted at two different farms to investigate the efficacy of using hCG to increase milk P₄ and pregnancy rates. In trial one, 79 lactating Holstein cows were exposed to the treatment protocol described in experiment 1. In addition to the milk sample collection schedule given in experiment 1, a sample was collected on day 0. Milk samples were stored at 4°C and later transported to the UBC laboratories for P₄ analysis. LSMeans for milk P₄ concentrations were different only at days 16 and 18 post breeding. Pregnancy rates were improved (P<0.01) by hCG treatments. The respective pregnancy rates for cows receiving hCG on day 0 (n=20), 7 (n=20), 14 (n=20) or control (n=19) were 25, 35, 35 and 21 %.
In the second trial, 121 lactating Holstein cows were randomly assigned to treatments as described earlier. Weekly milk samples were collected from each animal and assayed for P₄ as described above. LSMeans for milk P₄ were significantly different (P<0.05) among groups starting at day 14 until day 42 post breeding. hCG increased pregnancy rates over control cows. The pregnancy rates for cows treated on day 0, 7, 14 and control were 31, 50, 41 and 26 %, respectively.
In conclusion, this study revealed that treatment with hCG induced accessory CL development, increased P₄ production and improved pregnancy rates. It is evident, too, that treatment with hCG on day 7 post breeding may have greater potential for improving pregnancy rates not only in dairy and beef cattle but equally beneficial to the embryo transfer programmes. Increased pregnancy rates confirm the hypothesis that CL dysfunction does cost the livestock industry appreciable losses in embryos.Land and Food Systems, Faculty of
Graduate
29
Li, Suiyang. "Establishment of an inbreeding index in Holstein dairy cattle using DNA fingerprinting". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69763.
Testo completoAbstract (sommario):
In order to establish a method of assessing the degree of inbreeding within herds of cattle, we constructed a calibration index relating kinship and the degree of DNA band sharing in DNA fingerprints. Firstly, chickens were used as a model system to test the possibility of using microsatellite DNA as a probe for DNA fingerprinting in inbreeding analysis. Six genetic groups of chickens with estimated coefficients of inbreeding ranging from 0.026 to $>$ 0.98 (pedigree analysis) were fingerprinted using the minisatellite probe derived from M13 and the microsatellite probe (CAC)$ sb5$. The degree of band sharing using either probe increased in concert with the known amount of inbreeding and was described by the equation Y = 0.56X ($ pm$0.06) + 0.42 ($ pm$0.03); r = 0.998. Since in-gel hybridization using the microsatellite probes was faster and less labour intensive than using the minisatellite probe, it was used in the subsequent studies. Pedigree analysis in Holstein dairy cattle allowed for the empirical calibration of the association of band sharing with the coefficient of relatedness, (r), defined as the expected proportion of genes in 2 individuals that are identical by descent (i.e. for monozygous twins r = 1; for first order relatives r = 0.5; for half sibs r = 0.25 etc.). The average band sharing between pairs (6 pairs at each r value) of individuals within each class formed the basis for calibration. DNA was digested using RsaI. The relationship between band sharing and relatedness was well represented by a linear approximation Y = 0.51X ($ pm$0.09) + 0.50 ($ pm$0.04); r = 0.992. Using this calibration curve, random samples of animals within herds can be tested to establish the herd variability and to minimize inbreeding.
30
Kearney, John Francis. "Incorporation of new techniques in animal breeding programmes, with an emphasis on dairy cattle". Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/28328.
Testo completoAbstract (sommario):
A study of the inbreeding of UK Holstein cows was undertaken to assess the current levels and trends in inbreeding in this breed. Results showed that inbreeding has increased at a rate of 0.17% per year and it continues to increase in a linear fashion. Optimisation procedures, which have been developed to maximise the rate of genetic gain at a predefined rate of inbreeding, were applied to determine is such procedures would be useful in a dairy cattle context. The results showed that the procedures were able to generate more genetic gain at current rates of inbreeding or alternatively to reduce the rate of inbreeding at the current rate of genetic gain. Many resources have been devoted to the mapping of quantitative trait loci (QTL) of economic importance in most domestic livestock species. In the thesis a method is described to assess the benefits of using DNA tests at the commercial herd level. This method can be used for a variety of situations and two case studies were examined to illustrate the usefulness of the method. The first study dealt with the situation in which a breeder chooses to use a sire that is a carrier for a deleterious allele. The second case dealt with the availability of a DNA test for the A2 variant of the casein milk protein for which a premium is paid. Through a stochastic simulation, it is shown that pleiotropic QTL can result in a QTL segregating at constant frequencies in a population when the estimated polygenic correlation is zero. This has important implications when, for example, the traits under consideration are production and disease-type traits. Various selection strategies were investigated to determine genetic gain and changes in allele frequency when the underlying genetic model for the QTL was different in both traits.
31
Boukha, Aziza. "Genetic aspects of beef quality in Piemontese cattle and relations with breeding goal traits". Doctoral thesis, Università degli studi di Padova, 2008. http://hdl.handle.net/11577/3425501.
Testo completoAbstract (sommario):
The Piemontese breed is highly specialized for beef production due to double muscling (DM) inherited condition induced by a specific mutation of Myostatin gene (mh) located on Chromosome 2. This phenotype is characterized by greater muscle mass with less fat deposition, reduced weight of the skeleton reduced feed intake, and improved feed conversion.
The current breeding goal of the Piemontese population includes traits related to quantitative beef production and maternal calving performance of animals.
This thesis is aimed to study the possibility to introduce, indirectly, meat quality traits among the selected traits. This implies that genetic parameters and heritabilities for all meat quality traits need to be estimated.
Chapter 3 deals with the development and applications of a calibration curve for Near-Infrared spectroscopy (NIRS) aimed to predict chemical and physical compositions of Piemontese beef cattle.
Chapter 4 deals with the estimation of genetic parameters and heritabilities for physical meat quality traits, measured in laboratory, on a dataset of 1,080 Piemontese young bulls using a mixed linear Animal model. Chapter 5 aimed to Predict the fatty acid profiles on a dataset of 733 fresh samples of Longissimus thoracis muscle of Piemontese young bulls using the same regression developed by the calibration curve obtained with near infrared reflectance Spectroscopy (NIRS) technique, and to estimate heritabilities and additive genetic variations for NIRS-predicted traits.
Chapter 6 aimed to estimate variance and covariance components and corresponding genetic parameter estimates, and to estimate genetic and phenotypic correlations among meat quality traits in Piemontese beef cattle. (Co)variance components were estimated using a bivariate mixed animal model and was accomplished using Bayesian methodology and the Gibbs sampling integrations. Chapter 7 deals with the estimation of genetic correlations among beef quality traits and performance traits for Piemontese beef cattle, and to evaluate the possibility to include, indirectly, meat quality traits in the selection objective.
32
Tauck, Shaun Austin. "Factors associated with the biostimulatory effect of bulls on resumption of ovarian cycling activity and breeding performance of first-calf suckled beef cows". Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/tauck/TauckS0505.pdf.
Testo completo
33
Brown, Christopher Mark. "The application of recently developed techniques to Welsh Black Cattle in a group breeding scheme". Thesis, Bangor University, 1990. https://research.bangor.ac.uk/portal/en/theses/the-application-of-recently-developed-techniques-to-welsh-black-cattle-in-a-group-breeding-scheme(01ac6838-eb2d-4b05-9927-01574b3b68e2).html.
Testo completoAbstract (sommario):
Methods of superovulation, embryo recovery and embryo transfer were adapted and developed for application to Welsh Black cattle in a Group Breeding scheme. Three methods of oestrus detection in early postpartum suckling beef cows were evaluated. None was entirely reliable although a probe for the measurement of the electrical resistance of vaginal mucus was the most effective and the least stressful. The postpartum interval to superovulation did not affect the responses to treatment. The effect of suckling on embryo quality from superovulated Welsh Black cows was investigated. Three groups of cows (one dry and two suckling) were superovulated and their embryos recovered in two seasons; summer and autumn. Significant effects of season (P=O.016) and suckling (P=O.015) on embryo quality were detected. Season significantly affected the number of viable embryos (P=O.004). There were no effects on ovarian responses or on the numbers of embryos recovered. Nutritional supplementation and the administration of heG failed to improve embryo quality. Examination of the data from three years of superovulation and embryo recovery revealed significant monthly variations in % viable embryos (P=O.006) and in the numbers of viable embryos (P=O.02) recovered. Embryo recovery was not affected by the catheter used or by the side of uterus being flushed. The number of pari ties of the donor affected the ovulation rate (P=O.009) and the numbers of embryos recovered (P=O.028) but not the embryo recovery rate (%). No differences were detected in the superovulatory responses of cows bred by 3 methods nor from the method of oestrus synchronisation. Embryo transfers were performed by surgical and nonsurgical methods. Fresh and frozen embryos were successfully transferred by the surgical technique but no embryos transferred nonsurgically continued development. A measurement of cervical diameter was successful in identifying animals which were unsuitable for non-surgical embryo transfer and recovery procedures. n-Alkanes as nutritional markers for intake estimation were applied'to cattl~ in a performance test and to cows at pasture. The results obtained indicate that the method may be useful in the future development of selection methodologies for beef cattle. The findings of both series of investigations are discussed in relation to beef cattle improvement through Group Breeding schemes.
34
Ouma, Emily Awuor [Verfasser]. "Economic valuation of phenotypic cattle trait preferences in trypanosomosis prevalent production systems of Eastern Africa : implications for sustainable cattle breeding programs / Emily Awuor Ouma". Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019631376/34.
Testo completo
35
Almeida, Rodrigo de. "Study of abnormal test-days in Quebec Holstein cows". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23995.
Testo completoAbstract (sommario):
The influences of some environmental and genetic factors on the incidence of abnormal test-days in milk-recorded cows enrolled in the Quebec Dairy Herd Analysis Service (QDHAS) was determined in this study. Conditions Affecting Records (CAR) codes, collected monthly by QDHAS's supervisors, are possible explanation for a reduced production in the day of test. For the purpose of this study, CAR codes were used to analyze the incidence of health problems under generalized linear models methodology. Poisson and logistic regression model analyses were able to model the number of cases of abnormal test-days and health problems per lactation. Herd, testing program, parity number, and stage of lactation were important systematic effects included in the analysis. However, calving year, season of calving, and herd production level were not statistically significant in most analysis. Sires significantly differed in the incidence of some health problems of their daughters. Low heritability values, between 0.02 and 0.05, were found showing that most variability was explained by non-genetic factors. Regardless of the low heritability, the genetic variability has been shown to be considerable, suggesting that a significant genetic improvement of the disease resistance is achievable if proper procedures are adopted.
36
Do, Changhee. "Improvement in accuracy using records lacking sire information in the animal model". Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/39430.
Testo completo
37
Ilatsia, Evans D. [Verfasser], e Zárate Anne [Akademischer Betreuer] Valle. "Breeding strategies for Sahiwal cattle genetic resources in Kenya / Evans D. Ilatsia. Betreuer: Anne Valle Zárate". Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2011. http://d-nb.info/1027291856/34.
Testo completo
38
Williams, Anwen. "The use of herd data to teach dairy cattle breeding in further and higher education contexts". Thesis, Bangor University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421675.
Testo completo
39
Ahmad, Sausan. "Application of BLUP in prediction of breeding values and estimation of SNP effects in dairy cattle". Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12006/.
Testo completoAbstract (sommario):
Genetic selection for higher milk production has unavoidably resulted in a decline in fertility of dairy cattle in the UK due to the antagonistic correlation existing between fertility and milk yield. This trend in fertility has necessitated broadening the breeding programme to include fertility traits. However, the heritability of fertility traits currently used in the UK are of low heritability (h2<0.05). Therefore, one approach is to use molecular markers in order to identify animals with the highest genetic merit for fertility. The first aim of this project was therefore to test single nucleotide polymorphisms (SNPs) in candidate genes for their possible associations with fertility PTAs. A group of 408 dairy cows and bulls were genotyped at different loci (GnRH receptor, FSH receptor, LH receptor, activin receptor, and neuropeptide Y receptor Y2 (NPYRY2)). Seven SNPs were identified in the GnRH receptor gene. These were in the promoter and coding regions at positions -331, -108, 206, 260, 341, 383 and 410 relative to the translation start site. Two groups of SNPs were found to be in linkage disequilibrium, the SNPs at positions 206 and 383 being inherited together, as were those at -108, 260, 341 and 410. An association study between these SNPs and fertility PTAs revealed that the -108 SNP group was associated with favourable effects on fertility, reducing PTA for DFS by about 0.4 day. However, when GnRHR gene function was evaluated by measuring circulating LH level after administration of GnRH in pre-pubertal animals, no significant associations of the SNPs with LH levels were detected. Furthermore, five SNPs were identified in the FSHR at residues 502, 669, 596, 658, and 685, four of which (at positions 502, 669, 658, and 685), had deleterious effects on fertility PTAs, increasing CI and DFS, while decreasing NR56. Inaccurate heat detection has been identified as a major contributor to low fertility in dairy cattle, and therefore the second aim of this project was to investigate oestrus expression traits for which BLUP breeding values were estimated. Electronic tags (Fullwood and Lily) were used to measure behavioural activities at oestrus in two separate groups of animals. The first group comprised 103 cows in their first parity. Oestrus behaviour traits were: the number of steps at oestrus (STEPS) and the percentage increase in the number of steps at oestrus (STEPS%) relative to the number of steps over the 10 days preceding oestrus (BASE). Cows in this group were genotyped at 10 genes (GnRHR, LHR, FSHR, oestrogen receptors α and β (ESR), activin receptor, leptin, ghrelin, neuropeptide Y (NPY) and NPYRY2 for SNP identification. Of these SNPs, only those located in the GnRHR, oestrogen receptor α and NPY were found to have statistically significant effects on oestrus traits. The second group consisted of 189 cows with 995 oestrus behaviour records. Oestrus traits were: the number of activity units (AU) at oestrus (ACTIVITY) and the percentage increase in the number of AU at oestrus (ACTIVITY%) over baseline activity (BASE) determined over a 4 day rolling average. In addition to the above mentioned 10 genes, these cows were genotyped at signal transducer and activator of transcription 1 and 5A (STAT1, STAT5A), growth hormone receptor (GHR), prolactin, and prolactin receptor genes. In this study SNPs in the GnRHR, LHR, FSHR, ESRα, GHR, activin receptor, STAT1, and STAT5 were found to have significant effects on oestrus expression. The genetic basis for oestrus behaviour was also investigated applying various animal models in this group. ACTIVITY, ACTIVITY% and BASE had moderate heritabilities of 0.19 to 0.24, 0.16, and 0.25 respectively. The breeding values of the cows were shown to be normally distributed, and ranged between -19 to 27, -18 to 20, and -20 to 28 for ACTIVITY, ACTIVITY%, and BASE respectively. These values are significant in terms of the ability of the stockman to reliably detect cows in heat. There have in the past been few genetic analyses of oestrus behaviour characteristics, and there are few studies of SNP associations with fertility traits of the kind described here. Therefore these studies make a significant contribution to our understanding of the genetics of fertility in dairy cattle, and can be used by breeders as a means to improving fertility in the national dairy herd.
40
Schierenbeck, Sven Verfasser], Henner [Akademischer Betreuer] [Simianer e Hermann [Akademischer Betreuer] Swalve. "Controlling of dairy cattle breeding programs / Sven Schierenbeck. Gutachter: Henner Simianer ; Hermann Swalve. Betreuer: Henner Simianer". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://d-nb.info/1043765387/34.
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41
Espigolan, Rafael [UNESP]. "Parametric and semi-parametric models for predicting genomic breeding values of complex traits in Nelore cattle". Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/149846.
Testo completoAbstract (sommario):
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O melhoramento genético animal visa melhorar a produtividade econômica das futuras gerações de espécies domésticas por meio da seleção. A maioria das características de interesse econômico na pecuária é de expressão quantitativa e complexa, isto é, são influenciadas por vários genes e afetadas por fatores ambientais. As análises estatísticas de informações de fenótipo e pedigree permite estimar os valores genéticos dos candidatos à seleção com base no modelo infinitesimal. Uma grande quantidade de dados genômicos está atualmente disponível para a identificação e seleção de indivíduos geneticamente superiores com o potencial de aumentar a acurácia de predição dos valores genéticos e, portanto, a eficiência dos programas de melhoramento genético animal. Vários estudos têm sido conduzidos com o objetivo de identificar metodologias apropriadas para raças e características específicas, o que resultará em estimativas de valores genéticos genômicos (GEBVs) mais acurados. Portanto, o objetivo deste estudo foi verificar a possibilidade de aplicação de modelos semiparamétricos para a seleção genômica e comparar a habilidade de predição com os modelos paramétricos para dados reais (características de carcaça, qualidade da carne, crescimento e reprodutiva) e simulados. As informações fenotípicas e de pedigree utilizadas foram fornecidas por onze fazendas pertencentes a quatro programas de melhoramento genético animal. Para as características de carcaça e qualidade da carne, o banco de dados continha 3.643 registros para área de olho de lombo (REA), 3.619 registros para espessura de gordura (BFT), 3.670 registros para maciez da carne (TEN) e 3.378 observações para peso de carcaça quente (HCW). Um total de 825.364 registros para peso ao sobreano (YW) e 166.398 para idade ao primeiro parto (AFC) foi utilizado para as características de crescimento e reprodutiva. Genótipos de 2.710, 2.656, 2.749, 2.495, 4.455 e 1.760 animais para REA, BFT, TEN, HCW, YW e AFC foram disponibilizados, respectivamente. Após o controle de qualidade, restaram dados de, aproximadamente, 450.000 polimorfismos de base única (SNP). Os modelos de análise utilizados foram BLUP genômico (GBLUP), single-step GBLUP (ssGBLUP), Bayesian LASSO (BL) e as abordagens semiparamétricas Reproducing Kernel Hilbert Spaces (RKHS) e Kernel Averaging (KA). Para cada característica foi realizada uma validação cruzada composta por cinco “folds” e replicada aleatoriamente trinta vezes. Os modelos estatísticos foram comparados em termos do erro do quadrado médio (MSE) e acurácia de predição (ACC). Os valores de ACC variaram de 0,39 a 0,40 (REA), 0,38 a 0,41 (BFT), 0,23 a 0,28 (TEN), 0,33 a 0,35 (HCW), 0,36 a 0,51 (YW) e 0,49 a 0,56 (AFC). Para todas as características, os modelos GBLUP e BL apresentaram acurácias de predição similares. Para REA, BFT e HCW, todos os modelos apresentaram ACC similares, entretanto a regressão RKHS obteve o melhor ajuste comparado ao KA. Para características com maior quantidade de registros fenotípicos comparada ao número de animais genotipados (YW e AFC) o modelo ssGBLUP é indicado. Considerando o desempenho geral, para todas as características estudadas, a regressão RKHS é, particularmente, uma alternativa interessante para a aplicação na seleção genômica, especialmente para características de baixa herdabilidade. No estudo de simulação, genótipos, pedigree e fenótipos para quatro características (A, B, C e D) foram simulados utilizando valores de herdabilidade baseados nos obtidos com os dados reais (0,09, 0,12, 0,36 e 0,39 para cada característica, respectivamente). O genoma simulado consistiu de 735.293 marcadores e 1.000 QTLs distribuídos aleatoriamente por 29 pares de autossomos, com comprimento variando de 40 a 146 centimorgans (cM), totalizando 2.333 cM. Assumiu-se que os QTLs explicavam 100% da variação genética. Considerando as frequências do alelo menor maiores ou iguais a 0,01, um total de 430.000 marcadores foram selecionados aleatoriamente. Os fenótipos foram obtidos pela soma dos resíduos (aleatoriamente amostrados de uma distribuição normal com média igual a zero) aos valores genéticos verdadeiros, e todo o processo de simulação foi replicado 10 vezes. A ACC foi calculada por meio da correlação entre o valor genético genômico estimado e o valor genético verdadeiro, simulados da 12a a 15a geração. A média do desequilíbrio de ligação, medido entre os pares de marcadores adjacentes para todas as características simuladas foi de 0,21 para as gerações recentes (12a, 13a e 14a), e 0,22 para a 15a geração. A ACC para as características simuladas A, B, C e D variou de 0,43 a 0,44, 0,47 a 0,48, 0,80 a 0,82 e 0,72 a 0,73, respectivamente. Diferentes metodologias de seleção genômica implementadas neste estudo mostraram valores similares de acurácia de predição, e o método mais adequado é dependente da característica explorada. Em geral, as regressões RKHS obtiveram melhor desempenho em termos de ACC com menor valor de MSE em comparação com os outros modelos.
Animal breeding aims to improve economic productivity of future generations of domestic species through selection. Most of the traits of economic interest in livestock have a complex and quantitative expression i.e. are influenced by a large number of genes and affected by environmental factors. Statistical analysis of phenotypes and pedigree information allows estimating the breeding values of the selection candidates based on infinitesimal model. A large amount of genomic data is now available for the identification and selection of genetically superior individuals with the potential to increase the accuracy of prediction of genetic values and thus, the efficiency of animal breeding programs. Numerous studies have been conducted in order to identify appropriate methodologies to specific breeds and traits, which will result in more accurate genomic estimated breeding values (GEBVs). Therefore, the objective of this study was to verify the possibility of applying semi-parametric models for genomic selection and to compare their ability of prediction with those of parametric models for real (carcass, meat quality, growth and reproductive traits) and simulated data. The phenotypic and pedigree information used were provided by farms belonging to four animal breeding programs which represent eleven farms. For carcass and meat quality traits, the data set contained 3,643 records for rib eye area (REA), 3,619 records for backfat thickness (BFT), 3,670 records for meat tenderness (TEN) and 3,378 observations for hot carcass weight (HCW). A total of 825,364 records for yearling weight (YW) and 166,398 for age at first calving (AFC) were used as growth and reproductive traits of Nelore cattle. Genotypes of 2,710, 2,656, 2,749, 2,495, 4,455 and 1,760 animals were available for REA, BFT, TEN, HCW, YW and AFC, respectively. After quality control, approximately 450,000 single nucleotide polymorphisms (SNP) remained. Methods of analysis were genomic BLUP (GBLUP), single-step GBLUP (ssGBLUP), Bayesian LASSO (BL) and the semi-parametric approaches Reproducing Kernel Hilbert Spaces (RKHS) regression and Kernel Averaging (KA). A five-fold cross-validation with thirty random replicates was carried out and models were compared in terms of their prediction mean squared error (MSE) and accuracy of prediction (ACC). The ACC ranged from 0.39 to 0.40 (REA), 0.38 to 0.41 (BFT), 0.23 to 0.28 (TEN), 0.33 to 0.35 (HCW), 0.36 to 0.51 (YW) and 0.49 to 0.56 (AFC). For all traits, the GBLUP and BL models showed very similar prediction accuracies. For REA, BFT and HCW, models provided similar prediction accuracies, however RKHS regression had the best fit across traits considering multiple-step models and compared to KA. For traits which have a higher number of animals with phenotypes compared to the number of those with genotypes (YW and AFC), the ssGBLUP is indicated. Judged by overall performance, across all traits, the RKHS regression is particularly appealing for application in genomic selection, especially for low heritability traits. Simulated genotypes, pedigree, and phenotypes for four traits A, B, C and D were obtained using heritabilities based on real data (0.09, 0.12, 0.36 and 0.39 for each trait, respectively). The simulated genome consisted of 735,293 markers and 1,000 QTLs randomly distributed over 29 pairs of autosomes, with length varying from 40 to 146 centimorgans (cM), totaling 2,333 cM. It was assumed that QTLs explained 100% of genetic variance. Considering Minor Allele Frequencies greater or equal to 0.01, a total of 430,000 markers were randomly selected. The phenotypes were generated by adding residuals, randomly drawn from a normal distribution with mean equal to zero, to the true breeding values and all simulation process was replicated 10 times. ACC was quantified using correlations between the predicted genomic breeding value and true breeding values simulated for the generations of 12 to 15. The average linkage disequilibrium, measured between pairs of adjacent markers for all simulated traits was 0.21 for recent generations (12, 13 and 14), and 0.22 for generation 15. The ACC for simulated traits A, B, C and D ranged from 0.43 to 0.44, 0.47 to 0.48, 0.80 to 0.82 and 0.72 to 0.73, respectively. Different genomic selection methodologies implemented in this study showed similar accuracies of prediction, and the optimal method was sometimes trait dependent. In general, RKHS regressions were preferable in terms of ACC and provided smallest MSE estimates compared to other models.
FAPESP: 2014/00779-0
FAPESP: 2015/13084-3
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Espigolan, Rafael. "Parametric and semi-parametric models for predicting genomic breeding values of complex traits in Nelore cattle /". Jaboticabal, 2017. http://hdl.handle.net/11449/149846.
Testo completoAbstract (sommario):
Orientador: Lucia Galvão de AlbuquerqueCoorientador: Daniel Gustavo Mansan Gordo
Banca: Lenira El Faro Zadra
Banca: Ricardo Vieira Ventura
Banca: Danisio Prado Munari
Banca: Gerardo Alves Fernandes Júnior
Resumo: O melhoramento genético animal visa melhorar a produtividade econômica das futuras gerações de espécies domésticas por meio da seleção. A maioria das características de interesse econômico na pecuária é de expressão quantitativa e complexa, isto é, são influenciadas por vários genes e afetadas por fatores ambientais. As análises estatísticas de informações de fenótipo e pedigree permite estimar os valores genéticos dos candidatos à seleção com base no modelo infinitesimal. Uma grande quantidade de dados genômicos está atualmente disponível para a identificação e seleção de indivíduos geneticamente superiores com o potencial de aumentar a acurácia de predição dos valores genéticos e, portanto, a eficiência dos programas de melhoramento genético animal. Vários estudos têm sido conduzidos com o objetivo de identificar metodologias apropriadas para raças e características específicas, o que resultará em estimativas de valores genéticos genômicos (GEBVs) mais acurados. Portanto, o objetivo deste estudo foi verificar a possibilidade de aplicação de modelos semiparamétricos para a seleção genômica e comparar a habilidade de predição com os modelos paramétricos para dados reais (características de carcaça, qualidade da carne, crescimento e reprodutiva) e simulados. As informações fenotípicas e de pedigree utilizadas foram fornecidas por onze fazendas pertencentes a quatro programas de melhoramento genético animal. Para as características de carcaça e qualidade da carne, o banco de da... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Animal breeding aims to improve economic productivity of future generations of domestic species through selection. Most of the traits of economic interest in livestock have a complex and quantitative expression i.e. are influenced by a large number of genes and affected by environmental factors. Statistical analysis of phenotypes and pedigree information allows estimating the breeding values of the selection candidates based on infinitesimal model. A large amount of genomic data is now available for the identification and selection of genetically superior individuals with the potential to increase the accuracy of prediction of genetic values and thus, the efficiency of animal breeding programs. Numerous studies have been conducted in order to identify appropriate methodologies to specific breeds and traits, which will result in more accurate genomic estimated breeding values (GEBVs). Therefore, the objective of this study was to verify the possibility of applying semi-parametric models for genomic selection and to compare their ability of prediction with those of parametric models for real (carcass, meat quality, growth and reproductive traits) and simulated data. The phenotypic and pedigree information used were provided by farms belonging to four animal breeding programs which represent eleven farms. For carcass and meat quality traits, the data set contained 3,643 records for rib eye area (REA), 3,619 records for backfat thickness (BFT), 3,670 records for meat tenderness (... (Complete abstract click electronic access below)
Doutor
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Rosati, Giulio. "Design, characterization and validation of an innovative biosensor for illegal hypertrophy treatments detection in cattle breeding". Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424204.
Testo completoAbstract (sommario):
The work done during this PhD program, and presented in this thesis had the goal to design, develop and characterize a system for the detection of illegal anabolic treatments in cattle breeding, independently from the particular anabolic substance used. The system is aimed to allow for faster and cheaper controls with respect to standard techniques such as mass spectrometry, gas chromatography, and histological exams. Moreover, the system allows for on-the-field controls, drastically reducing the costs related to sample transportation, analysis, and trained personnel.
The main strength of this system is the independence of the anabolic treatments detection, from the particular substance employed, which makes this system optimal as screening method. Then, once identified the animals which has been treated, further analysis can be performed by standard techniques for the anabolic substance identification and quantification.
The independence from the anabolic substance is achieved by adopting a novel paradigm for anabolic treatments detection, based on the identification of a common hypertrophic effect induced by the anabolic substance on an in-vitro culture of mouse myogenic cells. The cells provided with the anabolic substances receptors, are engineered to react to the hypertrophic stimulus with the over-production of lactate, which is then released in the cell medium. Then, the lactate concentration in the medium is detected by an electrochemical enzyme-based biosensor, which allows for a rapid and precise quantification by a cheap and miniaturizable device. The quantification of lactate produced by the engineered cells allows the detection of on-going hypertrophic effect and thus of the presence of anabolic substances in the biological sample collected from the cattle.Il lavoro svolto durante questo dottorato di ricerca e riassunto in questa tesi ha avuto l'obiettivo di progettare, realizzare e caratterizzare un sistema unificato per la rilevazione di trattamenti anabolizzanti sui capi di bestiame bovini da carne, indipendentemente dalla sostanza utilizzata per i trattamenti. La tecnologia ideata consente di effettuare gli esami in modo molto più rapido che con i sistemi tradizionali e direttamente sul campo, su campioni d'urina dell'animale. Il suo principale punto di forza è l'indipendenza dal tipo di sostanza utilizzata che la rende ottimale per essere utilizzata come tecnica di screening. Una volta individuati gli animali trattati mediante il sistema, sarà possibile andare ad identificare e quantificare la sostanza anabolizzante mediante le tecniche standard di analisi. Tale indipendenza è ottenuta cambiando il paradigma di rilevazione delle sostanze e basandolo sull'effetto ipertrofico che queste hanno in vitro su una coltura di cellule miogeniche. L'effetto ipertrofico attiva nella linea cellulare miogenica, dotata dei recettori per le sostanze anabolizzanti e geneticamente modificata allo scopo, la sovraproduzione di acido lattico, che viene rilasciato dalla cellula nel mezzo. Qui l'acido lattico viene quindi quantificato da un biosensore elettrochimico enzimatico, grazie al quale è possibile ottenerne una veloce e precisa quantificazione con un'apparato di misura economico e miniaturizzabile. La quantificazione della concentrazione di acido lattico prodotto dalle cellule consente, a ritroso, di individuare la presenza di sostanze anabolizzanti nel campione d'urina dell'animale.
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Holm, Dietmar Erik. "The economic effects of an oestrus synchronisation protocol using prostaglandin and reproductive tract scoring in beef heifers in South Africa". Electronic thesis, 2006. http://upetd.up.ac.za/thesis/available/etd-05042007-162414/.
Testo completo
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Yilmaz, Ahmet. "VARIANCE COMPONENT ESTIMATION FOR REPRODUCTIVE TRAITS AND ANALYSES OF MYOFIBRILLAR PROTEINS AND AGE AT PUBERTY IN ANGUS BEEF CATTLE DIVERGENTLY SELECTED FOR BLOOD SERUM INSULIN-LIKE GROWTH FACTOR I CONCENTRATION". The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1041608790.
Testo completo
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Strasser, Mark. "The development of a fuzzy decision-support system for dairy cattle culling decisions". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ29794.pdf.
Testo completo
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Archer, Alfred Ainsley. "A framework to integrate and analyse industry-wide information for on-farm decision making in dairy cattle breeding /". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36749.
Testo completoAbstract (sommario):
The goal of this thesis was to develop a framework that could integrate and analyse industry-wide information for the support of on-farm decision-making in dairy-cattle breeding. Specific objectives included (i) describing a dairy breeding information system (DBIS); (ii) examining how the Internet could be exploited to improve the DBIS and its functioning; (iii) describing a process for implementing a unified data model to facilitate integrated user access to information in the DBIS; and (iv) developing software to support decision-making by facilitating access to a unified data model when implemented as a database management software.The first objective was achieved by following a systems approach---defining a goal, boundary, functions, structure and performance---to describe multi-organisational information systems and, specifically, a DBIS in the Canadian dairy industry. Using this framework, the subsequent analysis of the DBIS looked at its overall effectiveness. The DBIS was also compared with other known systems, where the number of participants (as well as their roles) differs from the Canadian situation. Improvements were suggested for the Canadian DBIS by focussing on the decision-maker's ability to retrieve, integrate and consider required information through information technologies. The second objective involved using the systems approach to investigate the kinds of information (if any) provided on Web sites of the DBIS participants, and to see if the Internet could be exploited to improve this process, either in terms of improved transfer speed or data transformation. It was established that the Internet is being used for rapid, flexible access to support information by DBIS participants, but that it is being under-utilised, particularly where herd output information is concerned. Herd output information could be filtered, integrated and transformed to support specific user needs at appropriate levels of intelligence density. It was further postulated that these data could be exploited more effectively through the use of such information technologies as common data exchange mechanisms and decision-support systems. The third objective was achieved through applying information engineering methods to develop a data model to represent the DBIS. This unified model was described in conceptual, logical and physical terms, and facilitated transparent access for on-farm users to information from more than one source organisation. It was demonstrated that such a model could maintain the autonomy of participating organisations while simultaneously creating an amalgamated databank for decisio
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Mashiloane, Majela Lesley. "Effect of selection at weaning on genetic parameters of weight gain for centralized and on farm test for beef bulls". Thesis, University of Limpopo (Turfloop Campus), 2007. http://hdl.handle.net/10386/788.
Testo completoAbstract (sommario):
Thesis (M.Sc.) (Agriculture) --University of Limpopo, 2007The objectives of this study were to evaluate the effect of pre-weaning selection on estimates of genetic parameters for post-weaning average daily gain in Phases C (ADG-C) and D (ADG-D) and to estimate genetic relationships between average daily gain in the two phases. Performance records of the South African Angus cattle breed was used in the analysis. (Co)variance components and genetic parameters for weaning (WWT), AGD-C and ADG-D were estimated by REML procedures fitting three different models (Models 1, 2 and 3) that differed in how they integrated sequential selection in the analysis of post-weaning traits. Model 1 was a univariate model of WWT, ADG-C and ADG-D. Model 2 was a two trait model of WWT and either ADG-C or ADG-D. Model 3 was a three trait model of WWT, ADG-C and ADG-D. Estimates of heritability for ADG-C were 0.39±0.08, 0.42±0.06 and 0.44±0.01 from Model 1, 2 and 3 respectively. Corresponding estimates of heritability for ADG-D were 0.18±0.021, 0.19±0.021 and 0.21±0.02 respectively. An estimate of genetic correlation between ADG-C and ADG-D was 0.58± and it suggested that the two traits may not necessarily be under the same genetic control. Rank correlations for all bulls based on ADG-C estimated breeding values (EBV’s) were 0.92, 0.83 and 0.94 for Model 1 vs. Model 2, Model 1 vs. Model 3 and Model 2 vs. Model 3 respectively. Corresponding ADG-D EBV’s rank correlations were 0.88, 0.84 and 0.93. Rank correlations for top and bottom 1%, 5% and 10% were lower than those for all bulls in both ADG-C and ADG-D. Low rank correlations showed that the difference in magnitude of genetic parameters from different models was enough to alter bull rankings based on EBV’s of ADG-C and ADG-D. Hence it was concluded that inclusion of pre-weaning information in genetic analysis for post-weaning average daily gain is necessary to account for selection at weaning.
the THRIP (Technology and Human Resource for Industry Project) and NRF (National Research Foundation).
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Ernst, Robin Tracy. "Virginia feeder cattle basis by season, location, sex, breed, weight and USDA grade differentials". Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44632.
Testo completoAbstract (sommario):
Explanatory feeder cattle basis models were developed for 16 different Virginia markets by season, futures contract month, weight, lot size, sex, breed and USDA grade differentials. The models are more disaggregated and explain up to 80 percent more of feeder cattle basis variation than any previous research. Since the variables in these explanatory models are all known in advance, these basis models are also predictive. Basis estimates from these models make it possible for a Virginia feeder cattle forward pricing agency to offer forward price and minimum price contracts to small size operators.
Master of Science
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Pitt, Colin John. "Lowering Sperm Dose Rates in Frozen Semen for Bovine Artificial Breeding". The University of Waikato, 2007. http://hdl.handle.net/10289/2232.
Testo completoAbstract (sommario):
The New Zealand Dairy industry relies on artificial breeding to produce high genetic merit replacement stock. Proven bull semen is extended and preserved as either ambient temperature product or as frozen doses. High fertility is essential to maintain synchronicity of lactation with the spring surge of grass growth. To improve efficiency in the utilization of the very best bulls producers try to lower sperm dose rates without compromising fertility. Livestock Improvement Corporation's (LIC) Long Last Liquid ™ (LLL) is most commonly used during the peak season and is their most important product. However, shortfalls and specifically targeted matings are met with frozen semen. Lowering sperm dose rates in both liquid and frozen semen maximises the usage of elite sires increasing genetic gain, lowering overheads and garnering premium prices for the semen producer. A product for improving frozen semen technology was developed whereby a discrete quantity of pretreated semen was placed alongside a beneficial post-thawing redilution medium in a standard semen straw. This emulated a larger-scale process developed to freeze semen in times of low demand and redilution into the LLL form for use as an ambient temperature product. This rediluted product has been proved to enhance semen survival and to allow fertility to be maintained at sperm dose rates lower than the widely accepted standard for frozen semen. The physical packaging of the semen into the industry standard single dose straw in a configuration that separated incompatible components was novel. This configuration was essential to prevent damage to the sperm during the freezing process from low solubility components in the post-thaw redilution medium. Separation between the semen and diluent within the straw was achieved by the introduction of a gas partition or air bubble between the two liquids. A large-scale field trial showed that the new product could produce savings of up to 25% of the sperm needed for a semen dose to achieve equivalent fertility. Furthermore, the production cost per dose was lowered in comparison to the standard semen processing system used at LIC.