Milk Yield In Dairy Cattle Research Articles

Factor analysis models for structuring covariance matrices of additive genetic effects: a Bayesian implementation

Multivariate linear models are increasingly important in quantitative genetics. In high dimensional specifications, factor analysis (FA) may provide an avenue for structuring (co)variance matrices, thus reducing the number of parameters needed for describing (co)dispersion. We describe how FA can be used to model genetic effects in the context of a multivariate linear mixed model. An orthogonal common factor structure is used to model genetic effects under Gaussian assumption, so that the marginal likelihood is multivariate normal with a structured genetic (co)variance matrix. Under standard prior assumptions, all fully conditional distributions have closed form, and samples from the joint posterior distribution can be obtained via Gibbs sampling. The model and the algorithm developed for its Bayesian implementation were used to describe five repeated records of milk yield in dairy cattle, and a one common FA model was compared with a standard multiple trait model. The Bayesian Information Criterion favored the FA model.

Genetic relationships among calving ease, calving interval, birth weight, and weaning weight in the Asturiana de los Valles beef cattle breed1

The aim of this paper was to estimate direct and maternal genetic parameters for calving ease (CE), birth weight (BrW), weaning weight (WW), and calving interval (CI) to assess the possibility of including this information in beef cattle improvement programs. Field data, including a total of 59,813 animals (1,390 sires and 1,147 maternal grand sires) from the Asturiana de los Valles beef cattle breed, were analyzed with a multivariate linear model. Estimates of heritability for direct genetic effects (CED, CID, BrWD, and WWD) were 0.191 +/- 0.019, 0.121 +/- 0.013, 0.390 +/- 0.030, and 0.453 +/- 0.035, respectively, whereas those for maternal genetic effects (CEM, BrWM, and WWM) were 0.140 +/- 0.015, 0.208 +/- 0.020, and 0.138 +/- 0.022, respectively. Genetic correlations between direct or maternal genetic effects across traits were, in general, positive and moderate to low. However, genetic correlation for the pair CED-BrWD was positive and high (0.604 +/- 0.064). Genetic correlations between the direct and maternal genetic effects within a trait were negative and moderate (-0.219 +/- 0.097 for CE, -0.337 +/- 0.080 for BrW, and -0.440 +/- 0.102 for WW). Genetic correlations for CED-BrWM and CED-WWM were -0.121 +/- 0.090 and -0.097 +/- 0.113, respectively. The genetic correlation for CEM-CID was unfavorable (0.485 +/- 0.078), and those for CEM-BrWD (-0.094 +/- 0.079) and CEM-WWD (-0.125 +/- 0.082) were low and negative. The genetic correlation between CID and WWM was favorable (-0.148 +/- 0.106). Overall, the data presented here support the hypothesis that maternal effects for CE and BrW are not the same and that the genetic relationships between CI and maternal effects for WW in beef cattle follow a similar pattern to that reported between CI and milk yield in dairy cattle. Moreover, the need to include direct and maternal breeding values in beef cattle selection programs is suggested.

Fit of different functions to the individual deviations in random regression test day models for milk yield in dairy cattle

The shape of individual deviations of milk yield for dairy cattle from the fixed part of a random regression test day model (RRTDM) was investigated. Data were 53,217 TD records for milk yield of 6,229 first lactation Canadian Holsteins in Ontario. Data were fitted with a model that included the fixed effects of herd-testdate, DIM interval nested within age and season of calving. Residuals of the model were then fitted with the following functions: Ali and Schaeffer 5 parameter model, fourth-order Legendre Polynomials, and cubic spline with three, four or five knots. Result confirm the great variability of shape that can be found when individual lactation are modeled. Cubic splines gave better fitting pe4rformances although together with a marked tendency to yield aberrant estimates at the edge of the lactation trajectory.

Leptin promoter mutations affect leptin levels and performance traits in dairy cows1

Leptin concentrations in body fluids and tissues undergo dynamic changes during the periparturient period. Polymorphisms in the leptin gene have been shown to be associated with differences in leptin concentration during late pregnancy but not during lactation. As the promoter of leptin regulates the expression of leptin, polymorphisms in this region could play an important role in the differences in leptin expression observed during the periparturient period. We sequenced the leptin promoter and discovered 20 SNP in a 1.6-kbp region of the bovine leptin promoter. Fourteen of these SNP were genotyped for all animals and these were found to be associated with leptin concentrations during late pregnancy but not during lactation. Three of these SNP are located in a 135-bp promoter region and together explained 14.3% of the variance in prepartum leptin concentrations which indicates that this region might be important for pregnancy-induced leptin synthesis. In the association study of the 14 SNP with dairy traits three were separately found to be associated with fertility, energy balance and protein yield. These might serve as markers for future breeding programmes for better fertility and energy balance without significantly influencing milk yield in dairy cattle.

Detection of Different Shapes of Lactation Curve for Milk Yield in Dairy Cattle by Empirical Mathematical Models

The study of relationships between mathematical properties of functions used to model lactation curves is usually limited to the evaluation of the goodness of fit. Problems related to the existence of different lactation curve shapes are usually neglected or solved drastically by considering shapes markedly different from the standard as biologically atypical. A deeper investigation could yield useful indications for developing technical tools aimed at modifying the lactation curve in a desirable fashion. Relationships between mathematical properties and lactation curve shapes were analyzed by fitting several common functions (Wood incomplete gamma, Wilmink's exponential, Ali and Schaeffer's polynomial regression, and fifth-order Legendre polynomials) to 229,518 test-day records belonging to 27,837 lactations of Italian Simmental cows. Among the best fits (adjusted r2 higher than 0.75), the 3-parameter models (Wood and Wilmink) were able to detect 2 main groups of curve shape: standard and atypical. Five-parameter models (Ali and Schaeffer function and the Legendre polynomials) were able to recognize a larger number of curve shapes. The higher flexibility of 5-parameter models was accompanied by increased sensitivity to local random variation as evidenced by the bias in estimated test-day yields at the beginning and end of lactation (border effect). Meaning of parameters, range of their values and of their (co) variances are clearly different among groups of curves. Our results suggest that analysis based on comparisons between parameter values and (co)variances should be done carefully. Comparisons among parameter values and (co)variances could yield more robust, reliable, and easy to interpret results if performed within groups based on curve shape.

Effects of a non-starch polysaccharidase enzyme preparation from Thermomyces lanuginosus on energy and protein metabolism and milk yield of dairy cattle

Non-starch polysaccharides (NSPs) form an integral part of the cell walls in plants and represent considerable available energy when degraded into absorbable mono-, di-, tri- and oligosaccharides. The ruminal microflora hydrolyses a good part of NSPs, however, recently there have been attempts to enhance the rate of utilisation by using external polysaccharidase enzymes. In the present study the effects of an enzyme preparation (Rumino-Zyme) high in xylanase activity were studied on ruminal volatile fatty acid (VFA) concentration, parameters of energy and protein metabolism, milk yield, feed conversion ratio (FCR) and body condition score of high-yielding dairy cows. A lignolytic enzyme preparation produced by the thermophilic fungus Thermomyces lanuginosus was applied in the present experiment and fed to dairy cows at 34 g/day dosage in the period between calving and the 110th day of lactation. This preparation increased VFA concentration in the rumen from about 32 days after calving and onward. Increased VFA concentration was followed by an about 5 to 10% increase in milk production and an almost 0.1% increase in butterfat production. Increased VFA concentration produced more balanced energy metabolism in the experimental cows as indicated by the lower incidence rate of hyperketonaemia, and lower acetoacetic acid and non-esterified fatty acid (NEFA) concentration in the blood of the experimental cows. Aspartate aminotransferase (AST) activity was tendentiously higher in the control group and the proportion of cows that had AST activity higher than 100 U/l was also higher in the control group. Both control and experimental cows showed balanced protein and acid-base metabolism throughout the experiment. Enhanced VFA concentration contributed to an improvement in energy balance in the experimental cows with a resultant improvement of feed intake and feed utilisation. Due to the more balanced energy metabolism postparturient body condition loss of the treated cows was reduced.

Selection indexes using calving interval, condition score and milk yield in dairy cattle

Increasing genetic merit for production has been associated with a decline in dairy cow fertility. In order to sustain lactation it appears that appreciable amounts of body condition are being mobilised, which may impinge on fertility. Body condition score (BCS) of first lactation heifers is recorded by Holstein UK and Ireland (HUKI) as part of its national type classification scheme. BCS may be a useful selection criterion for improving fertility. Calving dates and hence calving interval (CI) are generally very reliably recorded, but the usefulness of CI as a selection criterion is hampered for a number of reasons, one being that only the most fertile cows have two consecutive calving dates. This is a serious issue that still needs to be addressed. Our aim here was to investigate if there is genetic covariation between BCS and CI after adjustment for milk yield and to investigate selection responses in all three traits when selection is for each trait in turn and how responses are affected by restrictions imposing no genetic change in one of the traits. Restricting a trait to no change when it is correlated to a trait under selection may be important in developing customised indexes to satisfy specific requirements.

Influence of Trypanosoma evansi infection on milk yield of dairy cattle in northeast Thailand

Effect of subclinical Trypanosoma evansi infection on the milk yield of newly introduced Holstein Friesian dairy cattle were investigated. Five hundred pregnant heifers were introduced in Loei Province, northeast Thailand and a total of 168 blood samples were collected at 20 farms during 6 visits over 2 years. Trypanosomes were found in cattle in June and November 1996, after which the parasite was rarely seen. On the other hand, the infection prevalences by antigen-detection ELISA (Ag-ELISA) were around 40% from the first sampling through October 1997; then, antigenemic cattle decreased to 20% by June 1998. Milk yields of the cattle with detectable parasitaemia in June and November 1996 were significantly lower than those of the non-infected cattle by Student's t-test. Similarly, the milk yields of Ag-ELISA positive cattle were lower than those of negative cattle at every sampling and significant differences were observed during the first year and in February, 1998 (tested by 2-way ANOVA; T. evansi status and herd as factors). This study suggested that subclinical trypanosomosis caused decrease in milk yield of newly introduced dairy.

Runoff, Erosion, and Forage Production from Established Alfalfa and Smooth Bromegrass

AbstractSurface sealing of soils in established alfalfa (Medicago sativa L.) may produce runoff during intensive rainstorms, resulting in soil loss and reduced yield. We hypothesized that smooth bromegrass (Bromus inermus Leyss.) grown in mixture with alfalfa would reduce on‐site runoff and soil loss, and that this should offset any negative effect on forage quality. Alfalfa, smooth bromegrass, and an alfalfa‐smooth bromegrass mixture were established in 1992 on Rozetta silt loam (moderately well drained, fine‐silty, mixed, mesic Typic Hapludalfs) near Lancaster, WI. A 72‐mm h−1 simulated rainfall was applied for 1 h during the growing seasons of 1993 and 1994 to forage regrowth at 4 and 6 wk after first harvest and immediately after second harvest. The addition of smooth bromegrass to alfalfa did not significantly reduce runoff volume, sediment concentration, or total soil loss at any rainfall event at any stage of regrowth in either year. Furthermore, forage yield and concentrations of acid‐detergent fiber and crude protein in the forage were not affected. Averaged over both years and the three sward types, runoff at 6 wk was significantly less than at 0 wk, which was significantly less than at 4 wk. Total soil loss from all sward types summed over six simulated rainstorms was between 0.19 and 0.61 Mg ha−1, much less than the 11.2 Mg ha−1 yr−1 considered tolerable for this soil. Neutraldetergent fiber (NDF) concentration of bromegrass (534 g kg−1) was greater than either the mixture (441 g kg−1) or alfalfa (404 g kg−1). Soil loss and forage quality results do not support adding smooth bromegrass to alfalfa, especially since increased NDF results in lower forage intake by ruminants and reduced milk yield in dairy cattle (Bos taurus); however, livestock operations that could efficiently utilize smooth bromegrass monocultures could reduce soil loss and runoff by doing so.

Bovine respiratory syncytial virus reinfections and decreased milk yield in dairy cattle

The influence of Bovine Respiratory Syncytial Virus (BRSV) reinfections on the daily milk yield was studied by evaluating the milk production of 32 BRSV reinfected cows. For the estimation of milk production losses, four lactation curve models were used, including a gamma function, a second degree polynomial, and both of these models with a lag variable. Bovine respiratory syncytial virus reinfections seemed to have only a small effect on the daily milk production. Comparison of the true production with an estimated production according to the gamma function showed that the production for first lactation cows dropped 0.14 kg on average and for cows in their second or later lactation 0.56 kg on average, during 5 consecutive days in the infection period. For the second-degree polynomial model these values were respectively 0.42 kg and 0.80 kg. All calculated average production losses were relatively small and not significant (P > 0.15). The models without lag variable were more suitable than the models with the lag variable to estimate small production losses caused by BRSV reinfections. The power of this study was sufficient to detect a decrease in production of approximately 1-1.5 kg milk per cow per day. It was therefore concluded that BRSV reinfections were not associated with an important loss of milk production.

Response of Health Care to Selection for Milk Yield of Dairy Cattle

A selection experiment began during 1964 to measure long-term responses to selection of dairy cattle based only on milk yield. An unselected control group of cows was maintained as part of the experimental design. The four highest sires for PTA milk that were available from active AI were mated each year to cows of all generations in the selection group. Expenses for veterinary treatment, health supplies, drugs, and labor of animal attendants were recorded for each cow and categorized as mastitis, udder, edema, locomotion, digestion, ketosis, milk fever, reproduction, respiration, and other. Cows studied were born from 1975 to 1990. Over the 16-yr period, 236 selection and 227 control cows were observed while lactating. Cows in the selection group had greater health expenses as a correlated response to increased milk yield than did unselected controls. Lactational difference for genetic groups was $28.22 from an analysis of only first lactations and $49.44 from an analysis across parities. Expenses for mastitis accounted for most of the difference between genetic groups. Most health expense occurred during the first 20 d postpartum and increased for cows with successive lactations. During the 16-yr period, expense for selection cows increased more than for controls for reproduction, digestion, and ketosis, but not mastitis, udder (nonmastitis), edema, locomotion, milk fever, respiration, and other categories. Separate analyses of heifers from birth to initial calving and of dry cows provided little evidence of differences for genetic groups during nonlactating stages of life.

New Concepts in Carbohydrate Nutrition for High-Producing Cows

Structural carbohydrates: acid detergent fiber (ADF) and neutral detergent fiber (NDF) are utilized in dairy ration formulations as negative indicators of energy density. NDF has been identified as a predictor of dry matter intake, and ADF related more to digestibility. However, predictability of intake and digestibility from chemical parameters varies widely with forage type. Nonstructural carbohydrates (NSC) are a major energy source in high- producing-cow diets. Starch comprises the major portion of the total ration NSC fraction. Processing can influence rumen degradability of starch. Enzymatic methods and difference equations have been developed to quantitate NSC. Production studies have shown an optimal level of NSC to maximize milk yield. Rumen degradable carbohydrate/starch are emerging as qualitative measures in formulating dairy rations. Their usefulness in fine-tuning nutrient availability to the dairy cow for production purposes will be enhanced as larger data bases are developed and more production studies are conducted. The synergism between protein and carbohydrate use at the ruminai, pos- truminal, and mammary gland level will ultimately be key in maximizing efficiency of milk yield in dairy cattle.

The bovine pituitary‐adrenocortical axis and milk yield

A review is given of the available literature concerning the relationship between the bovine pituitary-adrenocortical axis and milk yield in dairy cattle. A severe drop in milk yield (more than 50%) can be induced by a single or repeated intramuscular injection of at least 200 IU ACTH or by a single intramuscular injection of 14.6 mg dexamethasone. Sixty minutes after an intravenous injection, both 200 IU ACTH and 100 mg cortisol are equivalent to a plasma cortisol concentration of at least 31 ng/ml. Thus the decrease in milk yield after an intramuscular injection of more than 200 IU ACTH can hardly be induced by cortisol only. The fact that bovine plasma hardly binds any dexamethasone, in sharp contrast with bovine mammary epithelial tissue, is a possible explanation of the special part which dexamethasone plays in milk yield.

Expected early genetic gain from selection for milk yield in dairy cattle

A matrix program to predict short term genetic gain from single trait selection for milk yield was developed. Rate of genetic gain was calculated as the annual change in the mean breeding value of all producing females. Several parameters sets representing various selection policies were used to examine situations pertinent to dairy populations of the United States. Approach to the asymptotic rates of genetic gain within the model varied with the choice of parameters, but even with consistent selection policies, predicted total genetic gain in the first 10 years was only half of the expected from classical theory. Considerable year to year variation in the rate of gain occurred. Early gains were more dependent on female selection decisions than gains during the steady state. In a two-phase model, the approach to the linear rate of gain in the second phase was accelerated by starting with an ongoing improvement program, but considerable delays still existed. Selection for sex- limited traits such as milk yield, which require pedigree selection and a waiting time for progeny test results reached asymptotic rates more slowly than previously assumed.

Selecting for Lactation Curve and Milk Yield in Dairy Cattle

Knowledge of genetic relationships between characteristics of lactation curves and lactation yields is essential for joint selection for both. An equation, yt = atbexp(−ct), was chosen to depict individual lactation curves for 5,927 first lactations by Holsteins in 557 herds in Michigan Dairy Herd Improvement where yt is daily milk yield at day t in lactation, a is yield at time zero, b is ascent to peak, and c is decline after peak. Genetic correlations for 305-day milk yield with initial production (a), ascent to peak (b), descent after peak (c), and peak yield were −.37, .40, 0, and .91.From empirical results from applied selection indexes, selecting for both increase of ascent to peak and peak yield did not decrease 305-day milk substantially. Rankings of sires on these indexes were similar to their rankings on milk yield alone. Attempts to decrease peak yield and increase persistency decreased milk yield greatly.

Induction of Lactation: Comparison of Injections of Estradiol—17β and Progesterone for 7 or 21 Days on Prolactin Response to Thyrotropin Releasing Hormone and Milk Yield in Dairy Cattle

Subcutaneous injections of estradiol-17β and progesterone (.10 and .25mg/kg of body weight) for 7 (group I) or 21 (II) days were used. Dexamethasone (.028mg/kg of body weight per day) or adrenocorticotropin (200 IU per day) was injected into cows in each group on days 18 to 20 (I) or 32 to 34 (II). Additionally, 100μg of thyrotropin releasing hormone was injected intravenously on days 1, 7, 17 (I) or 1, 7, and 31 (II). Milking was initiated on days 21 (I) or 35 (II). Overall 13 of 14 cows had mean daily yields of milk greater than 5kg; 12 had 305-day lactations. Yields of milk in cows injected for 21 days were greater on day 1 and increased more rapidly until peak was reached at 10 wk; daily mean production throughout lactation was greater (14.3 versus 10.1kg) than for cows injected for 7 days. Lactation curves pooled within cow within treatment differed. Concentrations of estradiol, estrone and progesterone increased during steroid injections and were 2- to 3-fold higher on day 21 in II than on day 7 (I or II), but concentrations of prolactin and total glucocorticoids in plasma did not differ during this time. The quantity of prolactin released in response to injection of thyrotropin releasing hormone was greater 10 days after steroid injections than before or during steroid injections. Preinjection concentrations of prolactin were correlated with magnitude of postinjection response to thyrotropin releasing hormone, but response was not correlated with concentrations of steroids in plasma on day of injection.

Estimation of the Effects of Season and Parity on Cumulative and Part-Lactation Milk Yield of Dairy Cattle in East Africa

Estimation of the Effects of Season and Parity on Cumulative and Part-Lactation Milk Yield of Dairy Cattle in East Africa

Genetic parameters for test-day milk yield in tropical Holstein Friesian cattle fitting a multiple-lactation random regression animal model

Accurate estimates of genetic parameters are essential for genetic improvement of milk yield in dairy cattle and for setting up breeding programmes. Estimates of genetic parameters from test-day models, particularly for Holstein Friesian cattle maintained in tropical environments, are scant in the literature. The objective of this study was therefore to estimate genetic parameters for milk yield by fitting a multiple-lactation random regression animal model (RRM) based on data from Ethiopian Holstein Friesian herds. Data were used from the first three lactations of cows that calved between 1997 and 2013. The data comprised 13 421 test-day milk yield records from 800 cows from two large dairy herds. Variance components were estimated using the average information restricted maximum likelihood method fitting an RRM. Heritability estimates for first, second, and third lactations ranged from 0.20 to 0.26, 0.15 to 0.27, and 0.17 to 0.28, respectively. Heritability estimates ranging from 0.15 to 0.28 indicate that effective genetic improvement should be accompanied by a corresponding improvement of the production environment. Across-lactation genetic correlations between first and second, second and third, and first and third lactations, expressed on a 305-day yield basis, were 0.88, 0.83, and 0.70, respectively. These genetic correlations, less than or equal to 0.88, indicate that different lactations are different traits. For an accurate evaluation of the genetic merit of animals for milk yield, lactations should be treated as different, but correlated traits in a multiple-lactation analysis.Keywords: Genetic correlation, heritability, Legendre polynomial, test-day model

Section G. General. Nonnutritional factors affecting milk yield in dairy cattle

Section G. General. Nonnutritional factors affecting milk yield in dairy cattle

The Maintenance of Milk Yield in Dairy Cattle in Kenya

The Maintenance of Milk Yield in Dairy Cattle in Kenya