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1
Pine, A. P., N. S. Jessop, and J. D. Oldham. "Effect of Protein Realimentation on Lactational Performance in Rats:." Proceedings of the British Society of Animal Production (1972) 1992 (March 1992): 115. http://dx.doi.org/10.1017/s0308229600022261.
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Previous research in our laboratory has shown that lactating rats given low protein diets will readily mobilise approximately 20% of body protein to sustain lactational performance. However in such females lactational performance falls markedly around day 6 of lactation and remains at this low level for the remainder of lactation. The objective of this study was therefore to investigate whether this decline in lactational performance coincided with the exhaustion of labile protein reserves, and secondly whether such protein depleted females could reestablish effective lactation in mid lactation when given an increased supply of dietary protein.Sixty six multiparous Sprague-Dawley rats were mated individually with a proven male breeder, mating being confirmed through the presence of vaginal plugs, then transferred to solid bottomed plastic cages for the remainder of the experiment.
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Downing, J. A. "An opportunity to revolutionise sow management." Animal Production Science 55, no. 12 (2015): 1411. http://dx.doi.org/10.1071/an15270.
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Research in any area of animal production can provide the opportunity to change how the system operates and is managed. The reliance on having to wean lactating sows to re-mate them has limited the commercial options for sow management. The desire to limit lactation length to maximise the litters per sow per year concurrently creates major challenges for such-aged piglets weaned abruptly. These issues are discussed in the review. This management system also fails to recognise that sows have the potential to spontaneously ovulate in lactation even when housed in farrowing crates. Inhibition of luteinising hormone release is the basis of lactational anoestrus with the suckling stimulus providing the strongest afferent signal to this inhibitory system. Any management strategy that reduces this inhibition has the potential to trigger lactational oestrus. In this review, group housing of sows, boar exposure and intermittent suckling are identified as strong stimuli that can promote lactational oestrus. Removing the need to wean sows to mate them offers further opportunities to change the way lactating sows are managed. One option is a two-stage lactation system in which the sows are housed in farrowing crates for the first 10–14 days and then moved to group accommodation for the remainder of lactation. This system provides welfare benefits for the litter in the early stage of lactation and then the benefits of less confinement for the sows in later lactation. Group lactation would also lend itself to the implementation of stimuli to assist the mating of sows in lactation, such as piglet separation and/or boar exposure. It also accommodates the mating of sows that spontaneously ovulate in lactation. Removing the need to wean sows to re-mate them provides the opportunity to increase weaning age and implement a gradual weaning, helping to attenuate the post-weaning growth check and potentially limiting antimicrobial use in weaner pigs.
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COROIAN, Cristian Ovidiu, Vioara MIRESAN, Aurelia COROIAN, Camelia RADUCU, Luisa ANDRONIE, Zamfir MARCHIS, Sorin TERHES, and Mircea Valentin MUNTEAN. "Biochemical and Haematological Blood Parameters at Different Stages of Lactation in Cows." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Animal Science and Biotechnologies 74, no. 1 (May 18, 2017): 31. http://dx.doi.org/10.15835/buasvmcn-asb:12283.
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The health status of cows is evaluated and depending on haematological and biochemical profile of blood. Nutrition is the main technological factor that can produce profound changes in the metabolic profile in animals (Dhiman et al., 1991; Khaled et al., 1999; Ingvartsen, 2006). Blood parameters analyze can lead to identify if there are errors in nutrition of lactating cows (Payne et al., 1970). The aim of this study was the evaluation of metabolic and biochemical changes that occur during colostrum period and in terms of number of lactations in cows. The biological material was represented by a total of 60 heads of dairy cows from a family farm from Sălaj County, Romania. The cows are all from Holstein breed and presented no clinical signs of any specific pathology. Blood samples were collected from the jugular vein of each cow and analyzed. 10 individuals from each of the six lactations have been randomly selected. Haematological and biochemical parameters showed variations depending on factors analyzed here. In lactation 1 Hb was 7.55±3.05 (g/dl), while in lactation 6 the value was 12.5±2.10 (g/dl). RBC ranged as follows: in lactation 1 - 28.50±2.05 and in lactation 6 - 30.02±2.05. Lymphocytes varied within very wide limits under the influence of lactation: in lactation 1 - 2.8±1.56 and in lactation 6 - 7.55±1.80. The number of lactations and lactation rank have influenced blood biochemical and hematological parameters in dairy cows. Biochemical parameters are influenced by post-partum day, showing the lowest values in the early days of colostral period and the highest in the last few days of the same period.
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Johnson, M. S., S. C. Thomson, and J. R. Speakman. "Limits to sustained energy intake." Journal of Experimental Biology 204, no. 11 (June 1, 2001): 1947–56. http://dx.doi.org/10.1242/jeb.204.11.1947.
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SUMMARYTo determine whether mice were limited in their capacity to absorb energy during late lactation, we attempted to increase the energy burden experienced by a group of female mice during late lactation by mating them at the postpartum oestrus, hence combining the energy demands of pregnancy and lactation. These experimental mice were therefore concurrently pregnant and lactating in their first lactation, and were followed through a normal second lactation. In a control group, females also underwent two lactations but sequentially, with the second mating after the first litter had been weaned. Maternal mass and food intake were measured throughout the first lactation, second pregnancy and second lactation. Maternal resting metabolic rate (RMR) was measured prior to the first mating and then at the peak of both the first and second lactations. Litter size and litter mass were also measured throughout both lactations. In the first lactation, experimental mice had a lower mass-independent RMR (F1,88=5.15, P=0.026) and raised significantly heavier pups (t=2.77, d.f.=32, P=0.0093) than the control mice. Experimental mice delayed implantation at the start of the second pregnancy. The extent of the delay was positively related to litter size during the first lactation (F1,19=4.58, P=0.046) and negatively related to mean pup mass (F1,19=5.78, P=0.027) in the first lactation. In the second lactation, the experimental mice gave birth to more (t=2.75, d.f.=38, P=0.0092) and lighter (t=−5.01, d.f.=38, P<0.0001) pups than did the controls in their second lactation. Maternal asymptotic daily food intake of control mice in the second lactation was significantly higher (t=−4.39, d.f.=37, P=0.0001) than that of the experimental mice and higher than that of controls during their first lactation. Despite the added burden on the experimental females during their first lactation, there was no increase in their food intake, which suggested that they might be limited by their capacity to absorb energy. However, control females appeared to be capable of increasing their asymptotic food intake beyond the supposed limits estimated previously, suggesting that the previously established limit was not a fixed central limitation on food intake. As RMR increased in parallel with the increase in food intake during the second lactation of control mice, the sustained energy intake remained at around 7.0×RMR.
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Pine, A. P., N. S. Jessop, and J. D. Oldham. "Maternal protein reserves and their influence on lactational performance in rats." British Journal of Nutrition 71, no. 1 (January 1994): 13–27. http://dx.doi.org/10.1079/bjn19940107.
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To determine the contribution of tissue protein reserves to lactational performance, multiparous female Sprague-Dawley rats were mated, caged individually and offered a diet high in protein (215 g crude protein (N × 6·25; CP)/kg dry matter (DM);H) ad lib. until day 12 of gestation. Subsequently half the rats continued to receive diet H while the remainder were offered a diet low in protein (65 g CP/kg DM;L) until parturition. This treatment aimed to produce a difference in carcass protein at parturition. On day 1 of lactation females were allocated to either diet H or a low-protein diet (90 g CP/kg DM; L2) offered until day 13 of lactation, giving four lactation treatment groups HH, HL2, LH and LL2. Groups of females were slaughtered on days 2 and 12 of gestation and days 1 and 13 of lactation and carcass and major organs were analysed. Weight gain of standardized litters was used as an indicator of lactational performance. Maternal carcass protein contents at parturition were 43·5 (SE 1·2) and 38·7 (SE 0·8) g (P < 0·01) for diets H and L respectively. During lactation there was little change in carcass protein content of HH rats while LH rats appeared to replenish their depleted reserves. Food intake or lactational performance did not differ between these two groups. HL2 and LL2 rats lost carcass protein with HL2 rats losing more than LL2 rats (P < 0·05). Intake and lactational performance were reduced compared with that on diet H (P < 0.05) but for the first 6 d of lactation were both greater (P < 0·05) for diet HL2 than for diet LL2. All four groups showed a considerable loss of body fat during lactation which was not affected by diet. The ability of HL2 rats to catabolize more protein and consume more food allowed them to sustain a greater lactationai performance. Previous maternal protein depletion had no influence on lactationai performance as long as an adequate supply of dietary protein was provided.
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Guliński, Piotr, and Ewa Salamończyk. "EVALUATION OF LACTATIONAL EXCRETION OF UREA AND AMMONIA IN DAIRY CATTLE HERDS." ANIMAL SCIENCE AND GENETICS 19, no. 1 (March 31, 2023): 69–82. http://dx.doi.org/10.5604/01.3001.0053.4120.
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The aim of the study was to evaluate the lactational unit production of urea and ammonia emissions from cows kept in eastern Poland. The study covered 1089 lactations of Polish Holstein-Friesian cows born between 1992 and 2018 in 15 cattle herds located in the Mazovia and Podlasie voivodships. The amount of urea excreted in urine and nitrogen compounds in cow feces was calculated based on the following regression equations: (y = 15.46 urea concentration in milk (g/L) + 193.4); y = 11.42 urea concentration in milk (g/L) + 41.93); y = 4.05 urea concentration in milk (g/L) + 151.47). Several factors affecting the total production of urea were examined. Four groups of animals were distinguished according to their milk yield from a 305-day lactation (<6000; 6001-8000; 8001-10000; >10000 kg); three groups based on year of birth (1992-2000; 2001-2010; 2011-2018); four age groups (first lactation; second lactation; third lactation; fourth to twelfth lactation); and three groups according to urea content in milk (1-150; 151-250; >250 mg/L). The results of the study showed that the average concentration of urea in cow urine was 78.6 kg and the ammonia emission from a lactating cow was 44.6 kg. The study demonstrated a large variation in the amount of nitrogen compounds excreted in feces and the degree of ammonia emission risk among animals. The main factors differentiating the amount of nitrogen compounds in urine and feces and the level of ammonia emission into the atmosphere included the cow's production level, year of birth, and urea content in milk.
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Kostomakhin, N., O. Voronkova, M. Gabedava, and E. Ermoshyna. "Dynamics of milk productivity of cows of Black-and-White breed by lactations." Glavnyj zootehnik (Head of Animal Breeding), no. 6 (June 1, 2020): 35–42. http://dx.doi.org/10.33920/sel-03-2006-05.
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The age of cow use is of big importance for the practice of dairy farming, since earlier culling of cows leads to a lack of milk, and later culling leads to the decrease in genetic progress. The purpose of the researches was to determine the dynamics of milk productivity of cows of Black-and-White breed by lactations. The researches have been carried out in the OJSC Breeding Farm “Oktyabrsky” in the Ferzikovsky district in the Kaluga region, where cattle of Black-and-White breed are bred. The object of researches was the breeding stock of Black-and-White cattle that had been lactating for five lactations. It has been found that the increase in milk yield occurred from I to IV lactation. For example, first-calf heifers had 6154,9 kg of milk yield and were statistically significantly inferior to cows of II lactation by 242,8 kg (P < 0,001) or by 3,9 %. The superiority of cows of III lactation over first-calf heifers in milk yield was 466,2 kg (P < 0,001) or 7,6 %. The maximum differences in milk yield between first-calf heifers and cows IV lactation were 704,8 kg (P < 0,001) or 11,5 %. Cows of V lactation also significantly outperformed of fi rst-calf heifers in milk yield by 381,6 kg (P < 0,01) or 6,2 %, but their milk yield was lower than that of cows during III and IV lactation. It has been revealed in the course of research that cows of all the studied lactations were characterized by sufficiently high milk productivity for cattle of Black-and-White breed. There was the increase in milk yield with the age of animals. The increase in milk yields dynamically occurs till IV lactation, and then their decrease is observed.
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Cui, Jian-Guo, Gang-Bin Tang, De-Hua Wang, and John R. Speakman. "Effects of leptin infusion during peak lactation on food intake, body composition, litter growth, and maternal neuroendocrine status in female Brandt's voles (Lasiopodomys brandtii)." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 300, no. 2 (February 2011): R447—R459. http://dx.doi.org/10.1152/ajpregu.00121.2010.
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During lactation, female small mammals frequently reduce their fat reserves to very low levels. The function of this reduction is unclear, as calculations suggest that the contribution of the withdrawn energy from fat to the total energy balance of lactation is trivial. An alternative hypothesis is that reducing fat leads to a reduction in circulating adipokines, such as leptin, that play a role in stimulating the hyperphagia of lactation. We investigated the role of circulating leptin in lactation by repleting leptin levels using miniosmotic pumps during the last 7 days of lactation in Brandt's voles ( Lasiopodomys brandtii ), a model small wild mammal we have extensively studied in the context of lactation energy demands. Repletion of leptin resulted in a dose-dependent reduction of body mass and food intake in lactating voles. Comparisons to nonreproducing individuals suggests that the reduced leptin in lactation, due to reduced fat stores, may account for ∼16% of the lactational hyperphagia. Reduced leptin in lactation may, in part, cause lactational hyperphagia via stimulatory effects on hypothalamic orexigenic neuropeptides (neuropeptide Y and agouti-related peptide) and inhibition of the anorexigenic neuropeptide (proopiomelanocortin). These effects were reversed by the experimental repletion of leptin. There was no significant effect of leptin treatment on daily energy expenditure, milk production or pup growth, but leptin repletion did result in a reversal of the suppression of uncoupling protein-1 levels in brown adipose tissue, indicating an additional role for reducing body fat and leptin during peak lacation.
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STEFANON, BRUNO, MONICA COLITTI, GIANFRANCO GABAI, CHRISTOPHER H. KNIGHT, and COLIN J. WILDE. "Mammary apoptosis and lactation persistency in dairy animals." Journal of Dairy Research 69, no. 1 (February 2002): 37–52. http://dx.doi.org/10.1017/s0022029901005246.
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The decline in milk yield after peak lactation in dairy animals has long been a biological conundrum for the mammary biologist, as well as a cause of considerable lost income for the dairy farmer. Recent advances in understanding the control of the mammary cell population now offer new insights on the former, and a potential means of alleviating the latter. The weight of evidence now indicates that a change in mammary cell number, the result of an imbalance between cell proliferation and cell removal, is a principal cause of declining production. Further, it suggests that the persistency of lactation, the rate of decline in milk yield with stage of lactation, is strongly influenced by the rate of cell death by apoptosis in the lactating gland. Mammary apoptosis was first demonstrated during tissue involution after lactation, but has now been detected during lactation, in mammary tissue of lactating mice, goats and cattle. Those factors that determine the rate of cell death by apoptosis are as yet poorly characterized, but include the frequency of milking in lactating goats. Initial evidence suggests that nutrition also is likely to influence cell survival after peak lactation, an important factor being the degree of oxidative stress imposed by feed and the tissue's ability to deal with, and prevent damage by, reactive oxygen species. Comparison of cows in calf or not pregnant during declining lactation also indicates a likely influence of reproductive hormones, with oestradiol and progesterone acting to preserve mammary ductal and alveolar integrity during the dry period, while allowing a degree of apoptosis and cell replacement. In each case, the molecular mechanisms controlling mammary cell survival (or otherwise) are as yet poorly defined. On the other hand, more persistent lactations are likely to benefit animal welfare through fewer calvings and by placing less emphasis on maximal production at peak lactation, and modelling of persistent lactation with longer calving intervals indicates their likely economic benefits. In these circumstances, there is considerable incentive to elucidate the determinants of mammary apoptosis, and the factors controlling the dynamic balance between cell proliferation and cell death in the lactating mammary gland.
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Liu, X., R. S. E. Brown, A. E. Herbison, and D. R. Grattan. "Lactational Anovulation in Mice Results From a Selective Loss of Kisspeptin Input to GnRH Neurons." Endocrinology 155, no. 1 (January 1, 2014): 193–203. http://dx.doi.org/10.1210/en.2013-1621.
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In mammals, lactation is associated with a period of infertility characterized by the loss of pulsatile secretion of GnRH and cessation of ovulatory cycles. Despite the importance of lactational infertility in determining overall fecundity of a species, the mechanisms by which the suckling stimulus suppresses GnRH secretion remain unclear. Because kisspeptin neurons are critical for fertility, the aim of this study was to test the hypothesis that reduced kisspeptin expression might mediate the lactation-induced suppression of fertility, using mouse models. In the rostral periventricular area of the third ventricle (RP3V), a progressive decrease in RP3V Kiss1 mRNA levels was observed during pregnancy culminating in a 10-fold reduction during lactation compared with diestrous controls. This was associated with approximately 60% reduction in the numbers of kisspeptin-immunoreactive neurons in the RP3V detected during lactation. Similarly, in the arcuate nucleus there was also a significant decrease in Kiss1 mRNA levels during late pregnancy and midlactation, and a notable decrease in kisspeptin fiber density during lactation. The functional characteristics of the RP3V kisspeptin input to GnRH neurons were assessed using electrophysiological approaches in an acute brain slice preparation. Although endogenous RP3V kisspeptin neurons were found to activate GnRH neurons in diestrous mice, this was never observed during lactation. This did not result from an absence of kisspeptin receptors because GnRH neurons responded normally to 100 nM exogenous kisspeptin during lactation. The kisspeptin deficit in lactating mice was selective, because GnRH neurons responded normally to RP3V gamma aminobutryic acid inputs during lactation. These data demonstrate that a selective loss of RP3V kisspeptin inputs to GnRH neurons during lactation is the likely mechanism causing lactational anovulation in the mouse.
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Brotherstone, Susan, W. G. Hill, and R. Thompson. "Components of environmental variance of yields of cows in different lactations." Animal Science 48, no. 2 (April 1989): 283–91. http://dx.doi.org/10.1017/s0003356100040289.
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ABSTRACTWith a view to incorporating identifiable environmental factors such as month of calving as random effects in models for dairy sire and cow breeding value estimation, an analysis was undertaken of environmental components of variance for fat yield in lactations 1 to 5 of pedigree British Friesian-Holstein cattle. Records of fat yield and of log fat yield on daughters of widely used sires were first corrected for age and month of calving and for sire in each lactation on a national basis. Variance components for herd-year, herd-year × lactation, herd-year × month of calving, herd-year × month of calving × lactation and error were then estimated for pairs of lactations.The results were most consistent for log fat yield, where heterogeneity of variance was less. Correlations were, approximately, 0·45 and 0·42 for records in the same herd-year and lactation for lactation 1 or a later lactation, respectively, and approximately 0·40 for records in the same herd-year and different lactations. Within herd-year and lactation, correlations of records in the same month were approximately 0·10 for lactation 1 and 0·08 for later lactations, and for different lactations the correlations were 0·06 if lactation 1 was included and 0·08 otherwise. Thus, the effects appear to be similar for later lactations, which can be pooled, but effects for month and month × lactation 1 v. later should be fitted.
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Broster, William H., A. June Clements, Valerie J. Broster, Tim Smith, Jonathan W. Siviter, and Randolph E. Hill. "Effect of amount and composition of feed given over three lactations on the performance of the dairy cow." Journal of Dairy Research 56, no. 4 (August 1989): 561–77. http://dx.doi.org/10.1017/s0022029900029083.
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SummaryEighty-nine autumn-calving first calf and adult Friesian cows participated in an experiment on the effect of feeding over three lactations on milk production and live weight change. Fixed daily allowances of digestible energy (DE) formed two of the treatments (high, H; moderate, M). Diets of similar composition were used for both treatments and rations were weighed daily for each cow. The cows within these treatments were re-randomized to H or M at second and again at third parturition on experiment. A further treatment (ALF), applied continuously over three lactations, consisted of the M allowance of compound feed, weighed daily for each cow, plus ad lib. weighed, group-fed forages. The ALF animals were randomized for each lactation into two groups both of which received the same total compound feed allowance over the first 26 weeks of lactation. For one group (Flat) equal amounts were given daily whilst for the other group (Step) the daily amount was decreased monthly. After week 26 equal rations were fed. Hay, maize silage and grass silage formed the forages in winter. Grass, cut for the H and M groups but grazed for the ALF group, provided the summer forage. Energy intakes covered some 80–110% of requirements (Alderman et al. 1975)Yields of milk and of milk solids responded similarly for both parities. In the first experimental lactation, treatment H led to greater yields compared with M. H also led to smaller losses of live weight in early lactation, equal gains in mid lactation, and smaller gains in late lactation and the dry period, compared with M. Extension of H into a second lactation increased the advantage in milk and solids yields observed in the first lactation on experiment. Recovery of body reserves on treatment M continued. Treatment H in a second lactation on experiment after M in the first lactation led to even greater compensatory gains in live weight at the expense of milk production. There was no effect in the third lactation on experiment of treatments applied in the first lactation. Treatments H and M applied factorially over lactations 2 and 3 gave the same pattern of treatment effects as in lactations 1 and 2. Treatment ALF broadly supported the same milk yield and live weight change as treatment H but improved fat, protein and lactose yields. Within treatment ALF, Flat and Step distribution of compound led to equal performance. Multiple lactation effects of ALF equalled those of H. The effects on milk composition of H compared with M treatment were variable. In general an advantage accrued to ALF over M but without long term effects.The effect of variation in intake on performance of the dairy cow has been extensively documented for short periods within lactations (Broster, 1972), and more so for milk production than live weight change. However, the evidence on the size and development of effects of variation in feeding over protracted periods within the adult life span of the dairy cow, e.g. some four lactations in the UK, is extremely limited (Broster & Broster, 1984; Broster et al. 1984), both for plane of nutrition and for diet composition. The problem has added point with the introduction of simplified feeding systems which lead to the provision of less attention to the individual cow than hitherto (Johnson, 1982; Leaver, 1986). This dearth of information on the long term feeding of the adult contrasts with the widely gathered evidence on the effect of feeding during rearing on the performance of the mature cow, which is also an important long term relationship. More multi-lactation research is needed and in the present trial, with both young and adult lactating cows, the effects of amount and composition of feed allowance over three lactations were studied.
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Elvira, Laura, Fernando Hernandez, Pedro Cuesta, Santiago Cano, Juan-Vicente Gonzalez-Martin, and Susana Astiz. "Factors affecting the lactation curves of intensively managed sheep based on a clustering approach." Journal of Dairy Research 80, no. 4 (September 4, 2013): 439–47. http://dx.doi.org/10.1017/s0022029913000381.
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This study investigated factors affecting milk production and lactation curves from complete lactations of Lacaune dairy sheep. Animals were part of a single flock under intensive management and were milked twice daily starting at lambing. The results of the analyses of 7788 complete lactations showed an average total milk yield of 434±183 l from lactations 234±63 d long, with an average lambing interval of 302±65 d. A Pollott additive mathematical model was used to estimate complete lactation curves. Clustering analysis identified four lactation types among Lacaune dairy sheep differing mainly in productivity i.e. milk yield per lactation (MY) and length of lactation (DIM). The so-called SL type involved short, less productive lactations (n=2137; 27·4%; MY=222±75·5 l and DIM=182±52·9 d). The SN type involved short lactations of normal productivity (n=2039; 26·2%; MY=396±73·7 l and DIM=205±33·1 d). The LP type involved long and productive lactations (n=2169; 27·9%; MY=487±70·5 l and DIM=265±40·7 d), while the LVP type included long and extremely productive lactations (n=1443; 18·5%; MY=694±114·0 l and DIM=295±54·7 d). Sheep showing the best lactation curves were usually younger than other sheep, and they had higher yield during the previous lactation, a shorter previous dry period (55±50·4 for LP and 61±55·0 d for LVP types) and longer lambing intervals. In addition, they tended to be born in September and to lamb in March, October and December. Sheep were remarkably stable in their lactation curve behaviour: the curve type observed for the first lactation was highly likely to persist in subsequent lactations (P<0·0001). These results suggest that farmers can use the shape of the first lactation curve to guide their selection of ewes for breeding and retention on the farm, thereby improving flock productivity.
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Sawa, A., and M. Bogucki. "Effect of extended lactations on cow milk and reproductive performance." Archives Animal Breeding 52, no. 3 (October 10, 2009): 219–29. http://dx.doi.org/10.5194/aab-52-219-2009.
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Abstract. Frequency of extended lactations and their effect on milk and reproductive performance of cows from the active population of 11 891 Black and White cows with different proportions of Holstein Fresian inheritance were analysed. It was found that lactations longer than a 305-day standard lactation were quite common in the analysed population of Black-and-White cows improved with the Holstein-Friesian breed. The age of cows, the level of yield in a standard lactation and season of the year had a significant effect on the proportion of extended lactations. Lactation extension had a beneficial effect on milk yield in full lactation but was detrimental to fertility. The efficiency of lactation extension was found to increase with the increasing level of yield in the standard lactation.
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Wijkstra, S., H. Moes, and T. R. Koiter. "Metabolism of pregnant-lactating rats is adapted to pregnancy rather than to lactation." American Journal of Physiology-Endocrinology and Metabolism 263, no. 4 (October 1, 1992): E766—E771. http://dx.doi.org/10.1152/ajpendo.1992.263.4.e766.
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In pregnant-lactating rats implantation was induced on day 4 of lactation so that, as an exception, lactation coincided with the period of high fetal growth. The already present suckling litters of these animals lagged behind in growth, but the "second" litters were at birth normal in size and weight. Such pregnant-lactating rats were tested in vivo with intravenous glucose loads and compared with cyclic and lactating rats. Glucose tolerance was unaffected by the reproductive state. Pregnant-lactating rats showed, just as during their first pregnancy, low basal glucose levels. Their basal insulin levels and insulin responses, however, were decreased in comparison with the first pregnancy and resembled those of lactating rats. This may be due to an increased insulin turnover, because in vitro insulin responsiveness and insulin content of both "pregnant-lactating" and "pregnant" islets were increased in comparison with "cyclic" and "lactating" islets. It was concluded that the metabolism of pregnant-lactating rats is adapted to the pregnant rather than to the lactational state.
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Knight, Christopher H., and Colin J. Wilde. "Milk production in concurrently pregnant and lactating goats mated out of season." Journal of Dairy Research 55, no. 4 (November 1988): 487–93. http://dx.doi.org/10.1017/s0022029900033252.
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SummaryFive lactating goats which had kidded normally in March were mated during seasonal anoestrus in May, at the time of peak milk production, after ovulation had been induced using gonadotrophin-releasing hormone (Knight et al. 1988). Milk yield was unaffected by the hormone treatment, and decreased at the same rate as that of control (non-pregnant) goats for the first 8 weeks of the pregnancy. Thereafter yield declined more quickly in the test goats and just before parturition (in October) was 57% of the control value. Following parturition in the test animals, yield rose rapidly as the second lactation was established. None became ‘dry’ at any stage. Yield continued to decline with advancing lactation in the controls, which were mated normally in October or November and dried-off in December. During their second (‘extra’) lactation in the winter the test animals produced 12% less than in a normal second lactation in summertime; during the year the extra lactation meant that the test animals produced 73% more milk than the controls. In some, a second concurrent pregnancy was established during the extra lactation, with the resuit that three lactations were obtained in the time normally taken for two. Mammary cell number and proliferation rate were both higher in the pregnant animals than in the controls in week 23 of the first lactation.
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van der Schoot, P., and W. J. de Greef. "Development of ovarian follicles during lactation in rats." Acta Endocrinologica 112, no. 2 (June 1986): 247–52. http://dx.doi.org/10.1530/acta.0.1120247.
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Abstract. Ovarian follicular development was studied during lactation in rats. At an early stage of lactation (day 7) the ovaries showed only small follicles in agreement with the expected 'follicular quiescence' during lactation. However, at a more advanced stage of lactation (day 14), there were large follicles which were capable of ovulation in response to exogenous gonadotropins. Unilateral ovariectomy early during lactation (day 2) resulted in compensatory follicular development in the remaining ovary. However, doubling of the number of large follicles per ovary had not yet occurred by day 13. Unilateral ovariectomy caused a significant prolongation of the delay of embryonic implantation in pregnant lactating rats: this probably reflected delay of the development of sufficiently large numbers of oestrogen-producing follicles for this process. Unilateral ovariectomy did not affect the length of lactational pseudopregnancy. The findings indicate that 'follicular quiescence' during lactation in rats is limited to the very first period after parturition. This limitation may result from the relative ineffectiveness of suckling to suppress the secretion of FSH. In this respect, ovarian follicular development in rats differs from that in many other species, including primates and man.
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Banos, G., G. Arsenos, Z. Abas, and Z. Basdagianni. "Population parameter estimation of daily milk yield of the Chios sheep using test-day random regression models and Gibbs sampling." Animal Science 81, no. 2 (October 2005): 233–38. http://dx.doi.org/10.1079/asc50030233.
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AbstractParameters of daily milk yield during the first three lactations of Chios ewes were estimated with random regression models. Data consisted of 42 675 test-day records of 7121 ewes from 75 flocks that had lambed between 1998 and 2000. Models fitted fourth order fixed regressions on Legendre polynomials of the number of days post partum and fourth order random regressions on the individual animal. (Co)variance components were estimated with Gibbs sampling. Lactations were analysed separately. The four eigen values accounted for 0·80 to 0·84, 0·11 to 0·15, 0·04 to 0·05 and about 0·01 of the animal variance, respectively, depending on lactation number. Animal variance estimates, including genetic and, partly, permanent environment effects, were high at the beginning of each lactation and decreased as lactation progressed, suggesting that the animal effect is most important to early daily records. Residual variance was highest in the middle of lactation, suggesting that non-systematic environmental factors play a bigger at that time. Animal correlation estimates between daily yield records ranged from 0·26 to 0·99, were highest for adjacent days and decreased for days further apart. The decline had a different shape in the three lactations and was more evident in the first, suggesting that the three lactations may be biologically distinct traits. Animal correlation estimates between daily and total lactation milk yield ranged from 0·61 to 0·98 and were highest in the middle and lowest towards the end of lactation. Early lactation daily yield had an animal correlation of 0·70 to 0·80 with total lactation milk yield, in all three lactations. Results of this study suggest that daily milk yield records in the early stages of lactation may be useful for selection of ewes with high producing ability and accurate prediction of total lactation milk yield.
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Kurilova, Anastasiia A., Alesya A. Bakhta, Larisa Y. Karpenko, Kirill Plemyashov, Anna I. Kozitcyna, Anna B. Balykina, Abram I. Enukashvili, Polina A. Polistovskaia, Olga N. Ershova, and Olga A. Dushenina. "PSX-2 Antioxidant system characteristics in Saanen goats depending on lactation period." Journal of Animal Science 98, Supplement_4 (November 3, 2020): 460–61. http://dx.doi.org/10.1093/jas/skaa278.803.
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Abstract Dairy goats require attention and high-quality feeding during the lactation due to metabolism intensity. The metabolic rate during different lactation periods in order to better understanding production physiology in Saanen goats is the case of interest. The aim of this research was to evaluate antioxidant system characteristics in Saanen goats depending on lactation period. The experiment was conducted in the north-western region of Russian Federation, in the laboratory of the biochemistry and physiology department, FSBEI of Higher Education «SPbSAVM». The experimental group included 30 Saanen goats, 2nd–3rd lactations, selected using matched pairs method. The blood samples were taken 3 times: at the start of the lactation (2 days after parturition), at peak lactation performance (45 days after parturition) and before the interlactation period (4 months after parturition). Control group included 30 non-lactating Saanen goats, same age. The blood samples in control group animal were taken once. The blood levels of lipid peroxygenation markers (malondialdehyde, dienketone and conjugated dienes) and superoxide dismutase and catalase activity were assessed by standard methods. Results presented as mean±standard error of the mean. Student’s t-test was used after proving normal distribution. Level of significance is labeled as P < 0.05. The results are displayed in table 1 and 2. After analyzing the received data of antioxidant system characteristics the free radical oxidation highest intensity were revealed at the start of the lactation and at peak lactation performance, which indicates the development of oxidative stress in this periods. Also antioxidant enzymes’ activity was reduced during the peak lactation performance and remained at the control group level at the start of the lactation. This indicates free radical oxidation processes decompensation during the peak lactation performance. Thus, due to the development of decompensated oxidative stress in high milk producing ability animals during peak lactation, exogenous use of anti-oxidants is recommended.
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Andersen, Fredrik, Olav Østerås, Olav Reksen, and Yrjo T. Gröhn. "Mastitis and the shape of the lactation curve in Norwegian dairy cows." Journal of Dairy Research 78, no. 1 (December 1, 2010): 23–31. http://dx.doi.org/10.1017/s0022029910000749.
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An investigation of the shape of the lactation curve and the mastitis incidence was conducted to identify whether management interventions of the lactation curve constitute a potential for reducing incidence of mastitis at herd level. Lactation curves were estimated to describe the variation of daily milk yield during the 305-d lactation period in Norwegian Red cows. Associations between mastitis incidence at herd level and lactation curve characteristics such as production level at onset of lactation, magnitude and time of peak milk yield, and increase and decrease of milk yield rates were studied. Data from 250 303 lactations occurring during 2005 and 2006 from 14 766 herds were obtained from the Norwegian Dairy Herd Recording System. Besides veterinary treatments, the records included information on monthly test-day milk yields. The shapes of the lactation curves at herd level were parameterized using a modified Wilmink model in two separate mixed model analyses. In the first analysis a subset of lactations with no records of veterinary treatments was used. Lactation curves from herds with high (>0·31 cases/305-d lactation) and low (<0·07 cases/305-d lactation) herd mastitis incidence rate were parameterized and compared for three separate strata of parity. The result showed that high herd mastitis incidence rate was associated with a low intercept (P<0·05), a steep slope before peak milk yield (P<0·01) and a rapid decline after peak milk yield (P<0·01). In the second analysis a subset of high-yielding lactations with veterinary treatments of mastitis only and lactations with no records of veterinary treatment were compared. This was done to investigate whether the findings at herd level were also reflected at cow level. These results showed that lactation curves from lactations with mastitis cases were associated with a steep slope before peak milk yield (P<0·05) in second and later parities and a rapid decline after peak milk yield (P<0·01) in all three parity groups.
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WÓJCIK, Piotr, Marzena CWYNAR, and Mateusz PANKOWSKI. "THE USE OF LACTATION PERSISTENCE AS AN INDICATOR IN THE SELECTION OF THE MATERNAL LINES OF HF COWS." Folia Pomeranae Universitatis Technologiae Stetinensis Agricultura, Alimentaria, Piscaria et Zootechnica 365, no. 64 (December 15, 2022): 76–85. http://dx.doi.org/10.21005/aapz2022.64.4.9.
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The research material for this study consisted of a group of 163 Polish Holstein Friesian cows (PHF). For the study, the cows were assigned to 14 maternal lineages covering three genera- tions. The aim of this study was to indicate possibilities for selecting cows with the goal of maintaining lineages on the farm which are characterised high productive qualities based on lactation persistency index. Basic milk parameters were analysed over a 305-day lactation cycle and information on somatic cell content was also gathered based on sample milkings. A characterisation of lactation persistency for a given lactation was generated as a percent difference between milk yield in the 2nd and 10th month of lactation, and a lactation persistency curve was developed for particular lineages in succes- sive lactations, representing changes in the productivity of the cows. It was determined that together with increasing numbers of lactations among the cows studied, the average lactation persistency index also increased. For younger cows, this index did not exceed 30%, while in the older group this index amounted to 70%. Cows with the highest lactation persistency values 70.1–80% were also char- acterised by the highest milk production in average daily milk yields during peak lactation, amount- ing to 56.14 kg at values of for the index. Cows which began their milk production stage with a high persistency index in the 1st and 2nd lactations, in successive lactations saw a significant decrease in this index. Breeding cattle within maternal lines characterized by a high and stable level of lactation persistence index can ensure a high level of milk production in this line of cows.
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Rodionov, G., N. Kostomakhin, L. Tabakova, G. Tabakov, A. Olesyuk, and A. Sokolovskaya. "Milk productivity of cows of different ages under the conditions of the dairy complex «Ryzhovo»." Glavnyj zootehnik (Head of Animal Breeding), no. 2 (February 1, 2020): 3–13. http://dx.doi.org/10.33920/sel-03-2002-01.
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When production of milk in industrial volumes it is necessary to monitor all processes aff ecting its quantity and quality: animal feeding, breeding, mode and method of milking, herd reproduction, labour organization in the dairy complex, creating favorable conditions for cows that correspond to physiological characteristics. The dairy industry continues to impose higher and higher demands on milk, so in addition to improving the milk productivity of cows, we must not forget about the quality of the product. The issues of milk yield of cows, fat and protein, yield of milk fat and protein, somatic cells in milk of cows of Black-and-White breed for a number of lactations in terms of the dairy complex “Ryzhovo” have been considered in the article. It has been noted be researches that in the 1st and 2nd lactations milk yield of animals was 10 621 and 10 553 kg, respectively. The highest productivity of the cows has reached in the 3rd and 4th lactations 11 365 and 11 655 kg, respectively, after which, in the 5th lactation there was a decrease in milk yield to 10 592 kg. When considering fat content for diff erent lactations, positive dynamics up to the 4th lactation inclusive has been revealed. Thus, the fat content in milk for the 1st lactation was 3,61 %, for 2nd – 3,68 %, for 3rd – 3,93 % and 4th – 4,00 %. In the 5th lactation fat content decreased to 3,78 %. It has been found when calculating the yield of milk fat in experimental cows for lactation that up to the 4th lactation inclusive the indicator increases: for the 1st lactation received 383 kg of milk fat, 2nd – 388 kg, 3rd – 447 kg, 4th – 466 kg, and for the 5th lactation, the decrease in the index to 400 kg. At the same time the yield of milk fat for the 5th lactation exceeds the 1st and 2nd. The protein content in the milk of cows of diff erent ages during the fi rst four lactations increases from 3,18 to 3,43 %. Then, in the 5th lactation there is the decrease in protein content to 3,35 %, however, this fi gure is second only to the highest the 4th lactation. It has been established that before the 3rd lactation the number of somatic cells in milk increases, then in the 4th lactation this indicator decreases (151,25 thousand/cm3 ) and in the 5th lactation reaches a maximum (242,27 thousand/cm3).
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KHAN, T. A., A. K. S. TOMAR, and TRIVENI DUTT. "Prediction of lifetime milk production in synthetic crossbred cattle strain Vrindavani of North India." Indian Journal of Animal Sciences 82, no. 11 (November 20, 2012): 1367–71. http://dx.doi.org/10.56093/ijans.v82i11.25156.
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Ten-year data records on growth (birth weight-BWt), five initially reproductive traits (age at first calving-AFC, first dry period-FSP, first dry period-FDP, first calving interval-FCI and first lactation length-FLL) along with the part lactation records of 100, 170 and 240days of first lactation (my100_1, my170_1 and my240_1) and second lactation (my100_2, my170_2 and my240_2) and their respective total milk yields (total lactation milk yield of first lactation- TLMY1 and total lactation milk yield of second lactation-TLMY2) were used to predict LTMY5 (lifetime milk yield as total milk yield up to 5 lactations) and LTMY4 (lifetime milk yield as total milk yield up to 4 lactations). It was observed that first calving interval (FCI) happens to be important predictor (out of initially expressed growth – birth weight(BWt), reproductive traits- AFC, FSP, FDP, FCI, FLL and first lactation milk traits- my100_1, my170_1, my240_1 and TLMY1) for lifetime prediction (both LTMY4 and LTMY5). Prediction of LTMY4 and LTMY5 with respect to initial growth (birth weight), reproductive traits (AFC, FSP, FDP, FCI, FLL) and first 2 lactations (my100_1, my170_1 my240_1, TLMY1, my100_2, my170_2 my240_2 and TLMY2) indicated the contribution of my240_2 followed by TLMY1 and my170_2. They jointly explained 40.32% variation in estimated value of LTMY4. However, prediction of LTMY5, with respect to these predictors showed my240_2 together with FLL jointly explained 26.71% variation in estimated value.
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Wagner, Brooklyn K., Alejandro E. Relling, Justin D. Kieffer, and Anthony J. Parker. "Brief communication: Plasma cortisol concentration is affected by lactation, but not intra-nasal oxytocin treatment, in beef cows." PLOS ONE 16, no. 7 (July 30, 2021): e0249323. http://dx.doi.org/10.1371/journal.pone.0249323.
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In mammals, including sheep and mice, lactation attenuates the hypothalamo-pituitary-adrenal axis and plasma cortisol concentration. Oxytocin, one neuropeptide present in the blood during lactation, may contribute to such stress attenuation. Providing oxytocin intra-nasally increases plasma oxytocin concentration in cattle and can be used in non-lactating cows to mirror plasma oxytocin concentration of lactating cows. Therefore, our hypothesis was that there would be no difference in plasma cortisol between non-lactating beef cows intra-nasally administered oxytocin and lactating beef cows intra-nasally treated with saline. Twenty Bos taurus cows were randomly allocated by lactational status to one of four treatments, in a 2×2 factorial arrangement: 1) Non-lactating, saline (NL-S; n = 5); 2) Non-lactating, oxytocin (NL-OXT; n = 5); 3) Lactating, saline (L-S; n = 5); and 4) Lactating, oxytocin (L-OXT; n = 5). Two hours pre-treatment, cows were catheterized, moved to their appropriate chute and baseline blood samples were collected at -60, -45, -30, and 0 minutes before treatments were administered. Directly following the 0-minute sample, cows were administered their intra-nasal treatment via a mucosal atomization device. Subsequently, blood was collected at 2, 4, 6, 8, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 minutes. Non-lactating cows had greater (P = 0.02) plasma cortisol concentration compared with lactating cows. There was no lactation by treatment interactions for either plasma cortisol (P = 0.55) or oxytocin (P = 0.89) concentration. Although a treatment by time interaction was identified for oxytocin (P < 0.0001), there was no main effect of lactation on plasma oxytocin concentration (P = 0.34). Similar oxytocin and dissimilar cortisol concentration in lactating and non-lactating cows indicate that oxytocin alone cannot be responsible for reduced plasma cortisol in lactating ruminants. Further investigations are needed to elucidate alternative mechanisms that may be involved in the stress hypo-responsive condition of lactating mammals.
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COULON, J. B., F. DAUVER, and J. P. GAREL. "Facteurs de variation de la numération cellulaire du lait chez des vaches laitières indemnes de mammites cliniques." INRAE Productions Animales 9, no. 2 (April 17, 1996): 133–39. http://dx.doi.org/10.20870/productions-animales.1996.9.2.4042.
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Les variations de la numération cellulaire du lait ont été analysées sur 404 lactations de 208 vaches laitières conduites sur un domaine expérimental de l’INRA et indemnes de mammites cliniques au cours des lactations considérées. En moyenne, la numération cellulaire a été minimale en 2ème mois de lactation (50 000 cellules/ml) et maximale en fin de lactation (200 000 cellules/ml). Les vaches primipares ont présenté des numérations plus élevées que les multipares en début de lactation et plus faibles en fin de lactation. Les vaches Holstein ont présenté des numérations cellulaires constamment supérieures à celles des vaches Montbéliardes et Tarentaises. En fin de lactation, l’écart entre ces 2 groupes d’animaux atteint environ 120 000 cellules/ml. Cet effet de la race n’est pas dû à un effet du niveau de production. Chez les vaches multipares, la présence de plus d’une mammite au cours des lactations précédentes a conduit à des numérations cellulaires significativement plus élevées (d’environ 40 000 cellules/ml à l’échelle de la lactation) que chez les vaches ayant présenté une mammite ou pas du tout au cours des lactations précédentes. La numération cellulaire augmente légèrement, indépendamment de l’effet du stade de lactation, au cours des mois d’août et septembre. L’ensemble de ces facteurs de variations ne permettent cependant pas d’expliquer des numérations cellulaires supérieures à 300 000 cellules/ml dans un lait de mélange.
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Cobuci, Jaime Araújo, Claudio Napolis Costa, José Braccini Neto, and Ary Ferreira de Freitas. "Genetic parameters for milk production by using random regression models with different alternatives of fixed regression modeling." Revista Brasileira de Zootecnia 40, no. 3 (March 2011): 557–67. http://dx.doi.org/10.1590/s1516-35982011000300013.
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Records of test-day milk yields of the first three lactations of 25,500 Holstein cows were used to estimate genetic parameters for milk yield by using two alternatives of definition of fixed regression of the random regression models (RRM). Legendre polynomials of fourth and fifth orders were used to model regression of fixed curve (defined based on averages of the populations or multiple sub-populations formed by grouping animals which calved at the same age and in the same season of the year) or random lactation curves (additive genetic and permanent enviroment). Akaike information criterion (AIC) and Bayesian information criterion (BIC) indicated that the models which used multiple regression of fixed lactation curves of lactation multiple regression model with fixed lactation curves had the best fit for the first lactation test-day milk yields and the models which used a single regression of fixed curve had the best fit for the second and third lactations. Heritability for milk yield during lactation estimates did not vary among models but ranged from 0.22 to 0.34, from 0.11 to 0.21, and from 0.10 to 0.20, respectively, in the first three lactations. Similarly to heridability estimates of genetic correlations did not vary among models. The use of single or multiple fixed regressions for fixed lactation curves by RRM does not influence the estimates of genetic parameters for test-day milk yield across lactations.
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Satoła, Alicja, and Ewa Ptak. "The eff ect of selected factors on urea concentration in the milk of Polish Holstein-Friesian cows." Roczniki Naukowe Polskiego Towarzystwa Zootechnicznego 12, no. 3 (September 29, 2016): 21–32. http://dx.doi.org/10.5604/01.3001.0013.5422.
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The objective of the study was to determine the relationships between milk urea concentration and factors such as lactation number, stage of lactation, month and season of the test day, age at calving, milk yield and protein percentage. Data for the calculations consisted of 7,731 test-day records from 1,078 Polish Holstein-Friesian cows. Test-day milking was performed for first, second and third lactations during the period from December 2010 to December 2011. Calculations were performed using the MIXED procedure in SAS/STAT. A mixed linear model using was applied in which parameters were estimated by the restricted maximum likelihood (REML) method. Least squares means for fixed eff ects in the model were compared by the Tukey-Kramer test. The first lactation diff ered significantly (p<0.05) from the second and third in terms of mean urea concentration, but there were no significant diff erences between the second and third lactations. For primiparous cows the milk urea concentration increased throughout lactation, but for older cows it increased only up to 7–8 months of lactation. Urea concentrations did not diff er significantly in the same stages of consecutive lactations, i.e. the first and second or second and third. Statistically significant diff erences were noted between the first and third lactations only in months 9 and 10 of lactation. Seasonal changes in milk urea content varied depending on the lactation number. In the first lactation the milk urea concentration was lowest in spring and highest in autumn. This tendency was not observed in the second and third lactation. Milk urea concentration was positively associated with both milk yield and protein percentage
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Curlewis, J. D., A. S. White, A. S. I. Loudon, and A. S. McNeilly. "Effects of lactation and season on plasma prolactin concentrations and response to bromocriptine during lactation in the Bennett's wallaby (Macropus rufogriseus rufogriseus)." Journal of Endocrinology 110, no. 1 (July 1986): 59–66. http://dx.doi.org/10.1677/joe.0.1100059.
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ABSTRACT Prolactin concentration was measured in plasma collected each week for 13 months from lactating and non-lactating Bennett's wallabies (Macropus rufogriseus rufogriseus). In non-lactating animals, prolactin concentrations decreased towards the end of the study but such changes did not appear to fit a seasonal pattern. Prolactin concentrations were low during early lactation and at a similar level to non-lactating animals, increased significantly during late pouch life (February–May), and then returned to non-lactating levels at a time coincident with permanent exit of the joey from the pouch. Temporary removal of joeys from their mothers in April was followed by a rapid decline in prolactin concentrations which remained low for 24 h until the joey was returned to its mother, whereupon prolactin concentrations increased significantly within 2 h. The effect of a single injection of bromocriptine (5 mg/kg) on lactation, embryonic diapause and plasma prolactin concentrations was examined at two stages of lactation. In November (lactational diapause), bromocriptine had no effect on prolactin concentrations but two out of four suckling joeys died on days 13 and 14 after treatment, and three out of four females gave birth on days 27, 27 and 28. Bromocriptine treatment in April (seasonal diapause) was followed by a significant reduction in prolactin concentrations and reduced growth rate of joeys belonging to treated females. New births were not observed. In view of the effect of bromocriptine on plasma prolactin concentrations in late lactation and the demonstration that domperidone (a dopamine antagonist) significantly increases plasma prolactin concentrations, it would seem that dopamine can act as a prolactin inhibitory hormone in this as in other mammalian species. J. Endocr. (1986) 110, 59–66
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Chaudhari, Pravin Nagibhai, Pratik Sanjaybhai Kapadiya, Mahesh Ramnivas Gadariya, Pranav Mayankbhai Gamit, and Bhagavanji Dayabhai Savaliya. "Test-day and other milk recording options for prediction of lactation milk yield in Jaffarabadi (Bubalus bubalis) buffaloes." Buffalo Bulletin 42, no. 3 (September 30, 2023): 397. http://dx.doi.org/10.56825/bufbu.2023.4234646.
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Generally, standard lactation milk yield is predicted based on test-day records collected at monthly intervals. Test-day milk production at different time intervals other than monthly intervals can be used to predict lactation milk yield of field bovines in field conditions. With the same possibility, this study was carried out to predict lactation milk yield in Jaffarabadi buffaloes from various test-day milk yield data retrieved for different time intervals. A total of 1,15,339 daily milk yield records in 176 lactations of 1st to 6th parity of 30 Jaffarabadi buffaloes lactating at the Cattle Breeding Farm, Kamdhenu University, Junagadh, Gujarat over a period of 28 years (1991 to 2018) were used for the study. Single monthly test-day milk yield recorded on 125th, 155th or 185th day i.e., 5th, 6th and 7th monthly test day yield alone provided only 50% reliability in determining the standard lactation milk yield. Daily peak yield alone was also found to be a poor predictor for lactation yield. Prediction equations using combination of consecutive two monthly test day yields from 4th to 10th monthly test day were found reliable source for prediction of lactation milk yield providing accuracy up to 82.19% whereas, daily peak yield in combination with single monthly test day yield at mid and late lactation was also predicted lactation milk yield with accuracies up to 72.23%. Milk production recorded at weekly interval could also be used to approximate milk production using the equation 15.35+6.91 × Sum of all weekly test-day yields, with precision of 98.93% or milk production recorded at fortnightly interval by the equation 18.04+14.65 × Sum of fortnightly test-day yields, with precision of 97.14%.
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Raducu, Camelia, Vioara Miresan, Aurelia Coroian, Ciprian Pop, Cristian Ovidiu Coroian, Daniel Cocan, and Luisa Andronie. "STUDY ON THE MILK QUALITY PARAMETERS IN THREE FARMS FROM SĂLAJ COUNTY." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Animal Science and Biotechnologies 73, no. 2 (November 28, 2016): 256. http://dx.doi.org/10.15835/buasvmcn-asb:12257.
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Milk quality is influenced by many factors including rank lactation. This study aims to present the evolution of the main quality parameters of milk as the fat, protein, lactose, dry matter and the number of somatic cells for the first five lactations in Bălţată Românească breed during twelve official controls, starting in June 2015 until the month of April 2016. The biological material studied was represented by herds of dairy cows in three farms from Sălaj County (Crasna, Marin and Bodia villages). Analyzing qualitative parameters of milk obtained from the herd in lactation 1 during the 12 controls, there was a percent of 3.50% fat, 3.05% protein, 4.49% lactose and 8.48% dry substance in farm from Crasna. These parameters varied over the five lactations, the highest values being ranked in lactation five. Herd from Marin farm presented a fat content of 4.44% in lactation 2, while the lowest percentage of fat was recorded in lactation 3 (3.66%). Regarding the protein, the highest percentage was obtained in lactation 2 (3.70%) and the lowest in lactation 1 (3.39%). Lactation rank affects milk quality, so in lactation 1 there were recorded the lowest values of quality parameters of milk.
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Memisi, N., M. Zujovic, Z. Tomic, and M. P. Petrovic. "Influence of lactation order and live weight on milk yield and fertility traits in domestic Balkan goat." Biotehnologija u stocarstvu 26, no. 3-4 (2010): 179–85. http://dx.doi.org/10.2298/bah1004179m.
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The goal of investigation in the domestic Balkan goat was to establish the effect of body weight and lactation number on milk yield and fertility. Research was done in herds belonging to private farmers, during a one-year period, on a total of 578 goats. Investigated herds were monitored also by lactation number, i.e. kidding number (lactations 1,2 and 3 individually, lactation 4 and following lactations investigated together). Body weight and milk yield were measured, while fertility was determined as the number of live born kids per 100 goats. Goats were also sorted into groups by age and body weight, while the interval within groups and between groups was 5 kg. Average total milk yield in the investigated population of the domestic Balkan goat was 177.5 kg. A statististically significant difference (P<0,01) was established for milk yield depending on body weight and age, except for goats in lactation 1 (P<0,05). In lactation 3 and 4, goats with body weights over 45 kg, comprising 30.23% of the total number in these groups, had the highest milk yields (over 200 kg). Pertaining to lactation number, i.e. kidding number, as well as body weight in both years of investigation, lowest fertility was found in lactations 1 and 2 (112%), and in goats with lowest body weight (25-30 kg), while this considerably increased lactation 4 and later lactations (136%), and body weights of over 40 kg (140%).
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Valdez, Susana R., Alicia B. Penissi, Ricardo P. Deis, and Graciela A. Jahn. "Hormonal profile and reproductive performance in lactation deficient (OFA hr/hr) and normal (Sprague–Dawley) female rats." Reproduction 133, no. 4 (April 2007): 827–40. http://dx.doi.org/10.1530/rep-06-0032.
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Lactation deficiency may have important consequences on infant health, particularly in populations of low socioeconomic status. The OFAhr/hr(OFA) strain of rats, derived from Sprague–Dawley (SD) rats, has deficient lactation and is a good model of lactation failure. We examined the reproductive performance and hormonal profiles in OFA and SD strains to determine the cause(s) of the lactation failure of the OFA strain. We measured hormonal (PRL, GH, gonadotropins, oxytocin, and progesterone) levels by RIA in cycling, pregnant, and lactating rats and in response to suckling. Dopaminergic metabolism was assessed by determination of mediobasal hypothalamic dopamine and dihydroxyphenylacetic acid (DOPAC) concentrations by HPLC and tyrosine hydroxylase expression by immunocytochemistry and western blot. OFA rats have normal fertility but 50% of the litters die of malnutrition on early lactation; only 6% of the mothers show normal lactation. The OFA rats showed lower circulating PRL during lactation, increased hypothalamic dopamine and DOPAC, and impaired milk ejection with decreased PRL and oxytocin response to suckling. Before parturition, PRL release and lactogenesis were normal, but dopaminergic metabolism was altered, suggesting activation of the dopaminergic system in OFA but not in SD rats. The number of arcuate and periventricular neurons expressing tyrosine hydroxylase was higher in SD rats, but hypothalamic expression of TH was higher in OFA rats at the end of pregnancy and early lactation. These results suggest that the OFA rats have impaired PRL release linked with an augmented dopaminergic tone which could be partially responsible for the lactational failure.
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Gootwine, E., and G. E. Pollott. "Factors affecting milk production in Improved Awassi dairy ewes." Animal Science 71, no. 3 (December 2000): 607–15. http://dx.doi.org/10.1017/s1357729800055387.
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AbstractThis study investigated the factors affecting milk production and lactation curve parameters from the complete lactations of Awassi dairy sheep. The animals were kept in a single flock under intensive management and milked twice daily starting at lambing. Lambs were removed from the ewes at birth into an artificial rearing unit. The results of the analyses of 3740 complete lactations showed a mean litter size of 1·28 lambs born per ewe lambing and average total milk yield of 506 l from lactations 214 days in length and with an average lambing interval of 330 days. Mean lactation number was 3·71 and ewes conceived on average in the 6th month of the lactation. The lactations peaked on day 45 at a yield of 3·44 l. The maximum milk secretion potential of the ewes was 3·9 l/day, with milk yield increasing at 62 g/day mid way between lambing and peak yield and declining at 16·5 g/day mid way between peak and the end of lactation. Age at first lambing, lactation number, litter size, month of lambing and month of conception during the lactation had significant effects (P < 0·05) on some or all of the lactation parameters investigated. Relatively high milk yield was obtained in lactations starting in the January to March period. The monthly effect on milk production was explained by significant (P < 0·05) heat load and photoperiod effects. High milk production was found to have a significant (P < 0·05) adverse effect on reproductive performance. Conception followed a significant (P < 0·05) short term variation in milk production.
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Horne, David S., Thomas G. Parker, William J. Donnelly, and D. Thomas Davies. "Factors affecting the ethanol stability of bovine skim milk." Journal of Dairy Research 53, no. 3 (August 1986): 407–17. http://dx.doi.org/10.1017/s0022029900025024.
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SUMMARYMilk samples from three groups of cows were taken at frequent intervals throughout lactation following autumn-, winter- or spring-calving. The ethanol (EtOH) stability/pH profile was determined for each sample and its characteristic parameters calculated. The lactational trends in these parameters were examined. Asymptotic maximum EtOH stability (Smax) was low in early lactation but rose rapidly to a value which showed no further lactational trends. Asymptotic minimum stability (Smin) for samples from autumn- and winter-calving cows showed a decrease which could be associated with the transition to summer grazing but no obvious lactational effects. The slope parameter increased slowly during lactation. The profile pK value decreased in early lactation, but thereafter increased throughout lactation giving the most obvious effect observed in direct measurement, namely an alkaline shift in the profile as lactation progressed. The EtOH stability calculated at a fixed pH of 6·6 passed through a maximum, characteristic for each cow, in the first weeks of lactation but declined steadily thereafter. This behaviour mirrors the lactational behaviour of the soluble salt balance ratio calculated from the original data of White & Davies (1958).
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CHEGINI, Arash, Navid GHAVI HOSSEIN-ZADEH, Hossein HOSSEINI-MOGHADAM, and Abdol Ahad SHADPARVAR. "Effect of somatic cell count on milk fat and protein in different parities and stages of lactation in Holstein cows." Acta agriculturae Slovenica 110, no. 1 (December 21, 2017): 37. http://dx.doi.org/10.14720/aas.2017.110.1.5.
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<p>The objective of this study was to investigate the effect of somatic cell score (SCS) on milk fat and protein in different parities and stages of lactation in Iranian Holstein cows. Records between June 2003 and January 2014 from 208,478 cows in lactations one to nine in 845 herds, comprising 2,456,303 monthly test-day (TD) records were used. The MIXED procedure of the SAS software with repeated measurements was used. The fixed effects of the model were herd, year-season of calving, month of TD, weeks of lactation, previous dry period length and somatic cell score (SCS) and covariate was calving age. Lactations were divided into six stages and analyses were performed within each stage. Also, different lactations were analyzed separately. Increase of SCS led to increase of milk fat and protein percentage and the increase of milk fat and protein associated with SCS was higher in early stages of lactation relative to later stages of lactation. Also, increase of milk fat and protein associated with SCS was higher in the first lactation rather than later lactations and decreased with increase of parity.</p>
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Reimer, A. B., and M. A. Hindell. "Variation in Body Condition and Diet of The Eastern Barred Bandicoot (Perameles gunnii) During the Breeding Season." Australian Mammalogy 19, no. 1 (1996): 47. http://dx.doi.org/10.1071/am96047.
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Body condition and diet of eastern barred bandicoots (Perameles gunnii) in southern Tasmania were quantified to investigate lactational strategies of a marsupial with medium-duration lactation and high reproductive output. There was no significant seasonal change in body condition, assessed using isotope dilution, or weight for either females or males. Further, body condition and weight of lactating females did not change with age of the pouch young, suggesting that female P. gunnii are able to cope with the energy demands of lactation without storing and utilising stored body fat. Analysis of faecal samples from April to October 1992 revealed a change of the frequency of occurrence of some prey items.
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Hodnett, D. W., H. F. DeLuca, and N. A. Jorgensen. "Bone mineral loss during lactation occurs in absence of parathyroid tissue." American Journal of Physiology-Endocrinology and Metabolism 262, no. 2 (February 1, 1992): E230—E233. http://dx.doi.org/10.1152/ajpendo.1992.262.2.e230.
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The requirement of parathyroid tissue for bone mineral loss during lactation was investigated. Lactating rats parathyroidectomized (PTX) at day 2 of lactation and consuming a 2% calcium diet are hypercalcemic and hypophosphatemic at day 13 of lactation. The high-calcium diet supports normal growth of pups nursing PTX mothers. PTX lactating rats mobilize bone mineral to the same extent as euparathyroid lactating rats consuming the same diet. Non-lactating PTX rats lose no bone mineral over a similar time period, indicating lactation-specific bone mineral mobilization in the absence of parathyroid tissue. PTX rats were verified to have physiologically insignificant amounts of parathyroid tissue, as evidenced by severe hypocalcemia and/or death in each rat after a shift from a 2% calcium to a 0.02% calcium diet. These results conclusively demonstrate that lactation-associated bone mineral mobilization does not require parathyroid hormone or parathyroid tissue.
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Ralević, R., T. Papović, I. Pihler, D. Kučević, M. Ivković, S. Dragin, K. Čobanović, C. Mekić, and M. Polovinski-Horvatović. "Influence of lactation number and parity on milk yield of Saanen goat’s breed." Arquivo Brasileiro de Medicina Veterinária e Zootecnia 73, no. 4 (August 2021): 923–28. http://dx.doi.org/10.1590/1678-4162-12283.
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ABSTRACT The aim of this research was to determine the influence of lactation number and parity on milk yield of Saanen goat’s breed. It has been concluded that milk yield was higher for goats that had given birth to twins and three kids than for goats that had given birth to a single kid (P<0.05). The longevity has a great positive impact on production, given that goats in the fifth lactation produced more milk than goats in first or second lactation (P<0.05), while goats in the sixth lactation still produced more milk than goats in first lactation (P<0.05). During the period from 2014- 2019, the research was conducted on a farm of multiparous Saanen goats in Vojvodina (northern part of Serbia). In the observed period, the farm had between 350 and 400 goats per milking, and the research included a total of 1,628 concluded lactations, within which the first lactations were the most 484, then the second 381. According to the number of lactations, goats were grouped into classes from one to seven and from one to three for parity. By comparing each individual lactation, it was determined that in first lactation goats produced significantly lower milk than goats in the rest lactations(P<0.05), except the seventh. Research has shown that lactation number has a significant influence on milk yield (P=0.00). Increasing the fertility of goats significantly affects the production capacity of dairy goats, since does with a larger number of kids in the litter had a significantly higher milk production (P<0.05). Due to the larger number of kids in the litter, milk production also increases. Likewise, it is assumed that the increase in milk yield of goats with two and three kids is a consequence of a larger placenta, i.e. stronger lactogenic activity during pregnancy.
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Walker, C.-D., J. B. Mitchell, and B. C. Woodside. "Suppression of LH secretion in food-restricted lactating females: effects of ovariectomy and bromocryptine treatment." Journal of Endocrinology 146, no. 1 (July 1995): 95–104. http://dx.doi.org/10.1677/joe.0.1460095.
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Abstract It has been shown that restricting food in lactating rats for the first 2 weeks postpartum at a level of 60% of the ad-libitum daily ration increases the length of lactational dioestrus by about 7 days but little is known about correlated changes in hormone levels. In the first experiment we report changes in LH, prolactin (PRL) and ACTH secretion in food-restricted and ad-libitum fed lactating rats at various stages of lactation. Our results demonstrate that food restriction during the first 2 weeks of lactation did not affect PRL or ACTH secretion, but decreased plasma LH levels despite comparable GnRH receptor density between food-restricted and ad-libitum fed females. In the second experiments we investigated a possible causal relationship between the increased secretion of progesterone seen in food-restricted females and the suppression of plasma LH levels, by determining the effects of bromocryptine treatment and ovariectomy on LH secretion in both ad-libitum fed and food-restricted lactating females. LH suppression in food-restricted lactating females was not affected by ovariectomy or bromocryptine treatment, although the latter treatment significantly increased GnRH receptor number. These data suggest that factors other than ovarian steroids, PRL or increased adrenocortical activity modulate LH secretion and the length of lactational dioestrus in food-restricted lactating females. Journal of Endocrinology (1995) 146, 95–104
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Madad, M., N. G. Hossein-Zadeh, and A. A. Shadparvar. "Genetic and phenotypic parameters for productive traits in the first three lactations of Khuzestan buffaloes in Iran." Archives Animal Breeding 56, no. 1 (October 10, 2013): 423–29. http://dx.doi.org/10.7482/0003-9438-56-041.
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Abstract. The objective of this study was to estimate genetic parameters for milk and fat yields in Khuzestan buffaloes of Iran. A total of 5 258 production records of the first three lactations of the Khuzestan buffaloes obtained from the Animal Breeding Centre of Iran between 1993 and 2009 were used for the analysis. Genetic parameters were estimated by the multivariate restricted maximum-likelihood (REML) procedure in the Wombat program. The averages of milk and fat production were 2 220.0 kg and 137.6 kg for first lactation; 2 236.8 kg and 137.9 kg for second lactation; and 2 303.6 kg and 143.3 kg for third lactation, respectively. Heritability estimates for milk and fat yields were 0.06 and 0.24 for the first; 0.06 and 0.28 for the second and 0.26 and 0.47 for the third lactation, respectively. Genetic correlation estimates between first and second, first and third, and second and third lactations were 0.77, 0.67 and 0.79 for milk and −0.61, −0.21 and −0.25 for fat yields. These estimates for milk yield are consistent with previous estimates obtained from animal models. Milk production of different lactations is essentially the same trait genetically and combining all lactation records as a single trait is appropriate. On the other hand, negative genetic correlations for fat yield in different lactations indicated that fat yields in all lactations were determined by different genes.
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Ignat'eva, Larisa, and A. Sermyagin. "BREEDING VALUE EVALUATION OF SIMMENTAL COWS BY LIFETIME PRODUCTIVITY DEPENDING ON AGE OF RETIREMENT AND ORIGIN." Bulletin of KSAU, no. 3 (March 5, 2024): 122–30. http://dx.doi.org/10.36718/1819-4036-2024-3-122-130.
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The purpose of research is to study the variability of genetic assessments of cows of different origins for traits of lifelong milk production when varying the age of retirement in the population of Simmental cattle in Russia. The analyzed database included breeding cows of the Simmental breed that were retired in the pe¬riod 2001–2020; the total number of livestock was 47,868 head. Calculation of the breeding value of productive longevity was carried out using the BLUPF90 program based on the BLUP Animal Model methodology. The share of Simmental cows of foreign selection that were eliminated after the 1st and 2nd lactations was 61.2 %, and those lactating longer than 6 lactations was only 4.0 %, while cows of Russian selection were 12.3 % less eliminated during the first two lactation and are able to produce longer. Phenotypic values of lifetime productivity in Simmental cows for an equal number of lactations are significantly higher in animals of foreign selection: from 824 kg of milk when leaving after the 1st lactation to 4,210 kg when leaving after the 10th lactation, from 35.3 to 188.5 kg by lifetime amount of fat and from 27.3 to 190.9 kg by lifetime amount of protein, respectively. The maximum estimates of breeding value for the lifetime productivity of a cow of fo¬reign selection reach +115.7 kg of milk fat and +91.3 kg of milk protein for a productive life by the 7th lactation.In cows of Russian selection, the predicted maximum breeding value estimates are achieved by the 9th lactation with indicators of +111.0 kg of milk fat and +88.4 kg of milk protein during the period of productive use. Lifetime milk productivity is significantly higher in Simmental cows of imported origin (by +824...+4210 kg), as well as estimates of breeding value (by +27.5...+35.9 kg), however, domestic Simmentals had a longer use period – on average for 2 lactations.
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Wilding, J. P. H., M. O. Ajala, P. D. Lambert, and S. R. Bloom. "Additive effects of lactation and food restriction to increase hypothalamic neuropeptide Y mRNA in rats." Journal of Endocrinology 152, no. 3 (March 1997): 365–69. http://dx.doi.org/10.1677/joe.0.1520365.
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Neuropeptide Y (NPY) is the most powerful appetite stimulant known, and rates of synthesis and release in the hypothalamus correlate closely with nutritional status. Pregnancy and lactation provide an excellent model of physiological hyperphagia. In this study the authors measured food intake, plasma glucose, insulin and luteinizing hormone (LH) and hypothalamic NPY mRNA in rats during pregnancy and in early and late lactation. The effect of food restriction (to 80% of control) during lactation was also studied. Pregnancy resulted in a modest increase in daily food intake over non-lactating controls (controls: 15·6±0·6 g, pregnant: 19·8±1·1 g, P<0·01) During lactation food intake increased dramatically to 355% of non-lactating levels by the 12th day. Insulin and glucose levels were unchanged in lactation, except in the food-restricted animals, when insulin levels were reduced to 49·5±18·4 pmol/l compared with 215±55 pmol/l (P<0·01) in lactating, non-restricted animals, and glucose was reduced to 3·7±0·2 mmol/l compared with 5·1 ± 0·2 mmol/l in non-restricted lactating animals. Hypothalamic NPY mRNA was unchanged in pregnancy, moderately increased after 5 days lactation (130±6·2% of control, P<0·01) and increased further at 14 days lactation (179 ± 14%, P<0·001). The greatest changes occurred in the animals who were food-deprived during lactation, when hypothalamic NPY mRNA levels reached 324 ± 44% (P<0·001) of non-lactating levels. Increases in hypothalamic NPY synthesis may be partly responsible for the increase in food intake seen in lactation, but unlike in food deprivation, the increase is not related to circulating insulin, suggesting involvement of other regulatory factors. Journal of Endocrinology (1997) 152, 365–369
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Podobed, Leonid, Yevgeniy Chigrinov, Mykola Kosov, and O. Bezaltychna. "DEPENDING OF RUMINATION DYNAMICS IN MILK COWS ON AGE IN LACTATION." Scientific and Technical Bulletin of the Institute of Animal Science NAAS of Ukraine, no. 129 (2023): 149–54. http://dx.doi.org/10.32900/2312-8402-2023-129-149-154.
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Rumination (duration of cud in cows per day) becomes an effective and reliable test that characterizes the general state of metabolism in their body, the process of digestion and the predicted level of productivity. In an experiment on an array of dairy cows at Petrodolinsky LLC, using a remote electronic control system with a SCR Heatime HR-IR feeding behavior monitoring function, the nature of rumination was observed depending on age in lactations. Studies have found that the average duration of rumination in cows in the herd changes during the lactation period depending on the age in lactations. The array of cows of the first lactation at the time of calving has the lowest rumination value, and its maximum is recorded in cows of the third lactation. By the 30th day of calving, the indicator of rumination activity in cows of all ages levels off, however, it remains the highest in animals of the second lactation. Only by 200 days of the lactation period, the difference in rumination of cows of all ages practically disappears. By the time of lactation cessation before calving, the intensity of rumination in cows of the first lactation again becomes lower than in older animals. It has been established that the first 30 days after calving in cows there is a close correlation between the increase in the amount of rumination and the level of milk yield. At the same time, the correlation coefficient for cows of the first lactation was 0.78, the second - 0.65 and the third - 0.63. When the maximum milk yield is reached (100–120 days of lactation), the correlation coefficient between the nature of rumination and the level of milk yield drops sharply, however, it remains the highest in cows of the first lactation (0.57) versus 0.48 and 0.42 in animals of the second and third lactations . However, in the phase of the second third of lactation, the corresponding indicator remains significant for characterizing the relationship between rumination and milk yield. The connection is significant and direct. After 200 days of lactation, the dependence of milk yield on the nature of rumination decreases even more and the correlation coefficient that determines this indicator is at the level of 0.28 (first lactation), 0.24 - second lactation and 0.23 - third lactation. The results of the research are of significant scientific and practical interest for determining changes in the nature of rumination in cows depending on age in lactation, assessing the age dynamics of the digestion process and establishing the relationship between the nature of rumination and the duration of economic use of animals and productivity. Keywords: cows, rumination, rumination activity, lactation, milk yield.
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Koçak, Ö., and B. Ekiz. "Comparison of different lactation curve models in Holstein cows raised on a farm in the south-eastern Anatolia region." Archives Animal Breeding 51, no. 4 (October 10, 2008): 329–37. http://dx.doi.org/10.5194/aab-51-329-2008.
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Abstract. The objective of this study was to compare the goodness of fit of seven mathematical models (including the gamma function, the exponential model, the mixed log model, the inverse quadratic polynomial model and their various modifications) on daily milk yield records. The criteria used to compare models were mean R2, root mean squared errors (RMSE) and difference between actual and predicted lactation milk yields. The effect of lactation number on curve parameters was significant for models with three parameters. Third lactation cows had the highest intercept post-calving, greatest incline between calving and peak milk yield and greatest decline between peak milk yield and end of lactation. Latest peak production occurred in first lactation for all models, while third lactation cows had the earliest day of peak production. The R2 values ranged between 0.590 and 0.650 for first lactation, between 0.703 and 0.773 for second lactation and between 0.686 and 0.824 for third lactation, depending on the model fitted. The root mean squared error values of different models varied between 1.748 kg and 2.556 kg for first parity cows, between 2.133 kg and 3.284 kg for second parity cows and between 2.342 kg and 7.898 kg for third parity cows. Lactation milk yield deviations of Ali and Schaeffer, Wilmink and Guo and Swalve Models were close to zero for all lactations. Ali and Schaeffer Model had the highest R2 for all lactations and also yielded smallest RMSE and actual and predicted lactation milk yield differences. Wilmink and Guo and Swalve Models gave better fit than other three parameter models.
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Krajinovic, M., I. Pihler, V. Simin, A. Jocic, S. Nicin, and M. Zujovic. "The influence of number of lactation on milk yield parameters in German fawn goats." Biotehnologija u stocarstvu 27, no. 4 (2011): 1469–75. http://dx.doi.org/10.2298/bah1104469k.
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Goat breeding is one of the least developed agricultural sectors in Serbia. This is reflected in the fact that the total number of goats in Serbia is less than 200,000, as well as the fact that no goat milk production has been recorded by the statistics. Over the last decade, there has been great interest of breeders for intensive breeding of highly productive goats, which resulted in imports of breeding goats. In the same period, several herds of the Alpine breed and German fawn goats were formed, while their production results in the growing conditions in our country have not been fully studied yet. During the first three lactations in the period 2003-2009, the following parameters of milk yield were studied: length of lactation, milk yield in one lactation, percentage and the milk fat yield, and percentage and the total protein yield. The average lactation period was 247 days for the first, 260.6 days for the second and 266.8 days for the third lactation. The average of milk yielded was constantly increasing from the first (594.51 kg) towards the third lactation (761.96 kg), showing statistically highly significant differences (P<0,001). What was also observed is that the order of lactation has not significantly affected the percentage of proteins in milk, whereas the total protein yield in lactations was influenced by the order of lactation due to the differences in average milk yield in lactations.
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Mizoguchi, Junji, and Tomonori Imamichi. "Decrease in amylase (EC 3.4.21.4) synthesis in lactating rats." British Journal of Nutrition 57, no. 2 (March 1987): 291–99. http://dx.doi.org/10.1079/bjn19870034.
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1. The amylase (EC 3.4.21.4) and trypsin (EC 3.2.1.1) activities in the pancreas in rats during pregnancy, lactation and after the weaning period, and the secretory responses to a secretagogue (caerulein) in the exocrine pancreas of lactating rats were measured.2. Trypsin activity increased as lactation progressed and reached twice that of unmated rats in the second half of the lactation period. The amylase activity fell before parturition and failed to recover even after the start of lactation and was significantly decreased throughout the lactation period.3. The total amount of pancreatic juice produced in the lactating rats was significantly greater than that of unmated rats; the amylase output was significantly less than that of unmated rats.4. When the pups were removed, amylase activity in the pancreas returned to the value in unmated rats. Furthermore, the amylase activity in lactating rats receiving a daily injection of insulin significantly exceeded that of normal lactating rats.5 These results indicate that the decrease in amylase activity in lactating rats is due to the reduction of amylase synthesis and there is a possibility that insulin is required for normal or elevated rates of amylase synthesis in lactating rats.
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Erskine, Ronald J., Paul C. Bartlett, Todd M. Byrem, Chelsea L. Render, Catherine Febvay, and Jessica T. Houseman. "Using a Herd Profile to Determine Age-Specific Prevalence of Bovine Leukemia Virus in Michigan Dairy Herds." Veterinary Medicine International 2012 (2012): 1–5. http://dx.doi.org/10.1155/2012/350374.
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Enzootic bovine leukosis is a contagious disease of cattle caused by the retrovirus, bovine leukemia virus (BLV) and is the most common cause of malignant neoplasm in cattle. In order to facilitate surveillance of this disease in dairy herds, we developed a method to combine ELISA of milk collected during routine production testing with a prescribed sampling of cows that is independent of the proportion of cows within each lactation. In 113 Michigan dairy herds, milk samples from ten cows in each of the 1st, 2nd, 3rd, and ≥4th lactations were analyzed for anti-Bovine Leukemia Virus (BLV) antibodies by milk ELISA. For each herd, a BLV herd profile (BHP) was calculated as the simple average of the percent of BLV-positive cows within each of the four lactation groups. The mean BHP for all herds was 32.8%, with means of 18.5, 28.8, 39.2, and 44.8% of 1st, 2nd, 3rd, and ≥4th lactation animals infected, respectively. In eight herds, we determined the correlation between the BHP, and true herd prevalence by testing the entire lactating herd (r=0.988, P<0.0001). The BHP allows discrimination of lactation-specific BLV prevalence within a dairy herd, to help identify risk factors and management plans that may be important in transmission of BLV.
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THAKUR, SWATI, R. HUOZHA, S. RAMANARAYANAN, S. DHARA, A. MAITI, and S. K. RASTOGI. "Influence of lactation stages on erythrocyte osmotic fragility of indigenous Badri cattle of Uttarakhand." Indian Journal of Animal Sciences 94, no. 3 (March 11, 2024): 280–82. http://dx.doi.org/10.56093/ijans.v94i3.141549.
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The aim of this study was to evaluate the influence of lactation stages on erythrocyte osmotic fragility. The study was carried out using forty healthy Badri cows divided into five groups with eight animals in each group during different stages of lactation, viz. 1 (0 to 60 days), 2 (61 to 120 days), 3 (121 to 180 days), 4 (181 to 240 days) and 5 (non-lactating animals) as control animals. The per cent haemolysis of erythrocytes among different lactation groups was found significant at 0.9% during mid and early late lactation i.e. 2 and 3 group and 0.5% saline concentration during all stages of lactation as well as non- lactating animals.
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Dyck, Hugo Richard, João Henrique Perotta, Taís Casonato Rodrigues, Julia Arantes Galvão, Juliana Sperotto Brum, and Ivan Roque de Barros Filho. "Occurrence of abomasal displacement in dairy cows from High-yielding dairy farms of Paraná State, Southern Brazil." Semina: Ciências Agrárias 44, no. 1 (February 6, 2023): 9–18. http://dx.doi.org/10.5433/1679-0359.2023v44n1p9.
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The present study aimed to verify the occurrence of displacement of the abomasum (DA) in dairy herds from a high-yielding dairy region of Southern Brazil. Data on breed, age, lactation number, days after calving, breeding system, number of animals, and number of lactating cows in the herd were obtained from 135 cases of DA. A total of 39 herds, and 6,454 cows, including 2,987 lactating cows from the municipality of Palmeira, Paraná State, were included in this study. The overall prevalence of DA was 2.09%, and occurrence of DA during lactation was 4.42%. Left displacement was more prevalent, with 94.07% of the cases. The mean number of lactations and age of the cows were 2.5±1.16 lactations and 50.9±18.5 months, respectively. DA occurred predominantly in the semi-intensive breeding system (68.1% of cases), during the first 4 weeks postpartum (84.4% of cases), in Black and White Holstein-Friesian cows (94.07% of cases), and during the winter (31.1% of cases). Cows with DA in high-yielding dairy farms in Southern Brazil were similar to cows from herds of high-milk-yielding regions of North America and Europe. Multiparous Black and White Holstein-Friesian cows showed the highest prevalence of DA during the transition period, mostly on the left side.
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Piccardi, Monica, Raúl Macchiavelli, Ariel Capitaine Funes, Gabriel A. Bó, and Mónica Balzarini. "Fitting milk production curves through nonlinear mixed models." Journal of Dairy Research 84, no. 2 (March 28, 2017): 146–53. http://dx.doi.org/10.1017/s0022029917000085.
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The aim of this work was to fit and compare three non-linear models (Wood, Milkbot and diphasic) to model lactation curves from two approaches: with and without cow random effect. Knowing the behaviour of lactation curves is critical for decision-making in a dairy farm. Knowledge of the model of milk production progress along each lactation is necessary not only at the mean population level (dairy farm), but also at individual level (cow-lactation). The fits were made in a group of high production and reproduction dairy farms; in first and third lactations in cool seasons. A total of 2167 complete lactations were involved, of which 984 were first-lactations and the remaining ones, third lactations (19 382 milk yield tests). PROC NLMIXED in SAS was used to make the fits and estimate the model parameters. The diphasic model resulted to be computationally complex and barely practical. Regarding the classical Wood and MilkBot models, although the information criteria suggest the selection of MilkBot, the differences in the estimation of production indicators did not show a significant improvement. The Wood model was found to be a good option for fitting the expected value of lactation curves. Furthermore, the three models fitted better when the subject (cow) random effect was considered, which is related to magnitude of production. The random effect improved the predictive potential of the models, but it did not have a significant effect on the production indicators derived from the lactation curves, such as milk yield and days in milk to peak.