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PubMed1985

Sire X environment interactions in beef cattle weaning weight field data.

Weaning weight field records, supplied by the American Polled Hereford Association, were used to examine sire X environment interactions. Sire X herd/region and sire X contemporary group/herd interactions were evaluated from a data set containing 19,503 records. Sire X region interaction was evaluated from a data set containing 8,659 records. The genetic correlations of sire progeny performance across contemporary groups/herd were .59 and .37 across herds and contemporary groups/region. The average genetic correlation of sire progeny performance across regions was .64. Heritability of weaning weight was .11 across regions, .17 within region and .28 within herd. Mixed-model sire analyses of Polled Hereford weaning weight field records should include sire X herd/region and sire X contemporary group/herd random effects to reduce the sire X environment effects particular to any herd or contemporary group, and to account for the distribution of sire progeny across herds and contemporary groups in the estimation of prediction error variance. It may be necessary to perform separate sire analyses for some regions to evaluate the breeding values of sires in regions where rank changes are likely to occur.

Animals↗

PubMed1988

Aggressive behavior of sows at parturition.

Sows, especially primiparous, may show aggressive behavior at parturition against their own piglets, resulting in wounding or death of the piglets. Frequency, environmental influences and heritability of aggressive behavior were studied in two data sets. The first (923 first litters) was collected at an experimental farm and the other (925 first litters) came from a pig breeding organization. Frequency of aggressiveness ranged, depending on its definition, from 7 to 12%. Fixed effects of year, season and feeding level of the gilt during the rearing period did not affect the frequency of aggressiveness. A regression of aggression on postpartum sow weight was found, suggesting that low weight at first farrowing might predispose sows to aggressive behavior. Coefficients for backfat and litter size were positive but nonsignificant. Heritability of aggressiveness on the underlying normal scale, estimated from the paternal half-sib component of variance, averaged .12 for the first data set, and .25 for data set II. Estimates from daughter-dam regression were .49 and .87 for the two data sets, respectively. A simulation study indicated that this difference might be due to maternal effects. A simple application would be to select boars and gilts from non-aggressive sows only. Response to selection would be rather slow if the frequency of aggressive behavior is low. At frequencies that are too high from an economic point of view, estimation of breeding values, combining own performance and(or) data from relatives, is required.

Aggression↗

PubMed2026

Effects of replacing sulfate with hydroxychloride sources of trace minerals on mineral status and production performance in dairy cows.

The objectives were to determine the effects of replacing sulfate with hydroxychloride sources of Cu, Mn, and Zn on mineral status and production performance in dairy cows. One hundred forty-one Holstein cows were stratified by parity group prepartum as nulliparous (lactation 0) or parous cows (lactation >0) and, within parity, cows were blocked by genomic breeding value for ECM yield (nulliparous cows) or recently completed lactation 305-d ECM (parous cows) and then randomly assigned to 1 of 2 treatments. Treatments were supplemental sources of Cu, Mn, and Zn as sulfate trace minerals (STM) or hydroxychloride trace minerals (HTM). Diets were formulated to contain approximately 16, 60, and 60 mg/kg of Cu, Mn, and Zn, respectively, and treatments were fed from 246 d of gestation to 105 d of lactation. Cows were weighed twice weekly prepartum and intake of DM, milk yield, and postpartum BW were measured daily, and composition of milk was analyzed twice weekly. Blood was sampled pre- and postpartum and hepatic tissue collected at 10 (50 STM and 52 HTM cows) and at 50 d postpartum (17 STM and 18 HTM cows) and analyzed for concentrations of minerals. Treatment did not affect intake or measures of energy balance prepartum. Numerical results between parentheses are presented following the sequence of STM and HTM. Concentrations of trace minerals in serum differed between treatments only prepartum and those of Cu (1.291 vs. 1.183 ± 0.031 mg/L) and Zn (1.307 vs. 1.211 ± 0.031 mg/L) were greater for cows fed STM compared with cows fed HTM; however, the opposite response was observed for serum Mn (1.628 vs. 1.754 ± 0.038 µg/L). Treatment did not affect liver Mn or Zn concentration, but for Cu, cows fed STM had greater concentration in the liver on d 10 postpartum compared with cows fed HTM (310 vs. 296 ± 7 mg/kg DM); however, the opposite response was observed on d 50 and cows fed STM had smaller concentration of Cu in liver than those fed HTM (287 vs. 318 ± 9 mg/kg DM). Cows fed HTM produced an additional 1.0 kg colostrum than STM cows (5.21 vs. 6.22 ± 0.63 kg), thus resulting in increased yield of colostrum solids. Treatment did not affect the content or yield of IgG in colostrum. Cows fed HTM produced 1.3 kg/d more milk (41.7 vs. 43.0 ± 0.5 kg/d) and 1.5 kg/d more energy-corrected milk (42.5 vs. 44.0 ± 0.6 kg/d) in the first 15 wk of lactation compared with cows fed STM. The estimated NEL content of the postpartum diet consumed by cows, after accounting for the different energy sinks and DMI, was 3.4% greater for HTM than STM (1.68 vs. 1.74 ± 0.02 Mcal/kg). Replacing sulfate with hydroxychloride sources of Cu, Mn, and Zn had small effects on the concentrations of those minerals in tissues and improved production performance in the first 15 wk of lactation.

Animals↗

PubMed2000

Whole genome scan to detect quantitative trait loci for conformation and functional traits in dairy cattle.

A granddaughter design was used to locate quantitative trait loci determining conformation and functional traits in dairy cattle. In this granddaughter design, consisting of 20 Holstein Friesian grandsires and 833 sons, genotypes were determined for 277 microsatellite markers covering the whole genome. Breeding values for 27 traits, regarding conformation (18), fertility (2), birth (4), workability (2), and udder health (1), were evaluated in an across-family analysis using multimarker regression. Significance thresholds were determined using a permutation test. The across-family analysis suggested the presence of 61 quantitative trait loci when 27 (i.e., one for each trait) were expected by chance. The test statistic exceeded the genomewise significance threshold for the following traits and chromosomes: chest width on chromosome 2; gestation length on chromosome 4; stature, body capacity, and size on chromosome 5; dairy character on chromosome 6; angularity on chromosome 12; fore udder attachment on chromosome 13; and fore udder attachment and front teat placement on chromosome 19. The quantitative trait loci for size traits on chromosomes 2, 5, and 6 may also have an effect on calving ease. The quantitative trait loci for udder traits on chromosomes 13 and 19 may also affect somatic cell score and mastitis resistance. If there are no negative effects on other economically important traits, marker assisted selection using markers associated with these quantitative trait loci can be applied.

Animals↗

PubMed2001

Genetic evaluation of dairy cattle using test-day models.

Recently there has been considerable interest in modeling individual test-day records (TDR) for genetic evaluation of dairy cattle as a replacement for the traditional use of estimated accumulated 305-d yields. Some advantages of test-day models (TDM) include the ability to account for environmental effects of each test day, the ability to model the trajectory of the lactation for individual genotypes or groups of animals, and the possibility of genetic evaluations for persistency of production. Also, the use of test-day models avoids the necessity of extending short lactations on culled animals and animals with records in progress. The disadvantages of TDM include computational difficulties associated with analyzing much larger datasets and the need to estimate many more parameters than in a traditional 305-d lactation model. Several different models have been proposed to model the trajectory of the lactation, including so-called "biological functions," various polynomials and character process models. At present, there is not universal agreement on which models to use in routine prediction of breeding values and better methods to compare models are desirable. Obtaining accurate estimates of the dispersion parameters to use in TDM remains a challenge. Methods used include a two-step procedure in which the dispersion parameters are estimated in a series of multivariate models followed by a reduction in order of fit using covariance functions, and a one-step procedure in which the parameters of TDM are estimated using restricted maximum likelihood or Bayesian methods in a random regression model. Further research should focus on including multiple lactation data and accounting for heterogeneity variance.

Algorithms↗

PubMed2002

Genetic parameter estimation for milk yield over multiple parities and various lengths of lactation in Danish Jerseys by random regression models.

The objectives of this study were to test for heterogeneity of genetic and environmental variance among completed and extended records from different lactations or different days in milk (DIM) and to build a model that accounts for this heterogeneity. A total of 147,457 305-d milk yield records from Danish Jersey cows calving between 1984 and early 1999 from two regions of Denmark were used in this study. Results showed that DIM and parity influenced parameters estimated from an animal model with repeated records. Therefore, the data were analyzed using random-regression models that allow the covariance between measurements to change gradually with DIM and parity. Random regressions were fitted for additive genetic effects and permanent environmental effects using second- or third-order normalized Legendre polynomials for DIM and parity. Variances of random-regression coefficients associated with all orders of the polynomials were significant. Based on these parameter estimates, a covariance function (CF) was defined. The CF showed that the heritability decreases over parities, but within each parity heritability increases with DIM, whereas variance of permanent environmental effects increases over parities and decreases with DIM. Generally, genetic correlations were higher between records with similar DIM and parity. The results indicate that there are problems with the extension procedure used to predict 305-d milk yields. Using the covariance functions estimated in this study, breeding values could be predicted that take into account the covariance structure between records from different parities and different DIM.

Analysis of Variance↗

PubMed2003

Quantitative trait loci mapping of functional traits in the German Holstein cattle population.

A whole-genome scan to detect quantitative trait loci (QTL) for functional traits was performed in the German Holstein cattle population. For this purpose, 263 genetic markers across all autosomes and the pseudoautosomal region of the sex chromosomes were genotyped in 16 granddaughter-design families with 872 sons. The traits investigated were deregressed breedingvalues for maternal and direct effects on dystocia (DYSm, DYSd) and stillbirth (STIm, STId) as well as maternal and paternal effects on nonreturn rates of 90 d (NR90m, NR90p). Furthermore, deregressed breeding values for functional herd life (FHL) and daughter yield deviation for somatic cell count (SCC) were investigated. Weighted multimarker regression analyses across families and permutation tests were applied for the detection of QTL and the calculation of statistical significance. A ten percent genomewise significant QTL was localized for DYSm on chromosome 8 and for SCC on chromosome 18. A further 24 putative QTL exceeding the 5% chromosomewise threshold were detected. On chromosomes 7, 8, 10, 18, and X/Yps, coincidence of QTL for several traits was observed. Our results suggest that loci with influence on udder health may also contribute to genetic variance of longevity. Prior to implementation of these QTL in marker assisted selection programs for functional traits, information about direct and correlated effects of these QTL as well as fine mapping of their chromosomal positions is required.

Animals↗

PubMed2003

Bayesian estimation of parameters of a structural model for genetic covariances between milk yield in five regions of the United States.

Inference about genetic covariance matrices using multiple-trait models is often hindered by lack of information. This leads to imprecise estimates of genetic parameters and of breeding values. Patterns in a genetic covariance matrix can be exploited to reduce the number of parameters and to increase quality of inferences. A structural model for genetic covariances was developed and fitted to milk yield data in five regions of the United States. This was compared with a standard multiple-trait analysis using a deviance information criterion, a measure of quality of fit. Data consisted of 3,465,334 Holstein first-lactation records from daughters of 43,755 sires in five regions of the United States (Midwest, Northeast, Northwest, Southeast, Southwest). Parameters of the structural model included an intercept and effects of measures of genetic and of management similarity on genetic covariances. Genetic similarity depended on the number of records contributed by sires that were common to a pair of regions. Management similarity was a function of the quantity of concentrate used to produce 1000 kg of milk in each pair of regions. The structural and the multiple-trait models gave similar estimates of genetic covariances, but the number of parameters was 8 in the former vs. 15 in the latter. Hence, estimates of genetic covariances were more precise with the structural model. A deviance information criterion suggested a slight superiority of the multiple-trait model, although probably within sampling error. For both models, genetic correlations between milk yield in five regions of the United States were larger than 0.93.

Analysis of Variance↗

PubMed2003

Genetic effects on stillbirth and calving difficulty in Swedish Holsteins at first and second calving.

In Swedish Holstein dairy cattle, genetic effects on stillbirth and calving difficulty were studied in 411,409 first- and 281,193 second-calvers. A linear single-trait sire-maternal grandsire model and a threshold model using a Gibbs sampling technique were used to analyse calving data from 1985 to 1996. In first calving when using the linear model, the heritability of stillbirth on the visible scale was 4% for the direct effect and 3% for the maternal effect. For calving difficulty it was 6% and 5% for direct and maternal effects, respectively. In second calving the corresponding heritabilities for the two traits were considerably lower, less than 1%. Adjusting for calving difficulty in linear analysis of stillbirth halved the heritabilities for the direct and maternal effects in first calving. When using a threshold model, heritabilities for stillbirth in first-calvers were 12% and 8% for direct and maternal effects, respectively, and for calving difficulty they were 17% and 12%. At second calving corresponding heritabilities were 2 to 4% for stillbirth and 4 to 7% for calving difficulty. The correlation between direct and maternal effects was around -0.1, irrespective of whether the linear or the threshold model was used for first-calvers. The genetic correlations between bulls' EBV from first and second calving were 0.4 to 0.5 for direct and maternal effects in stillbirth, whereas they were 0.6 to 0.7 for calving difficulty. In first-calvers there was a substantial genetic variation in both traits, expressed by differences between breeding values of bulls, despite fairly low heritability. The results obtained in this study suggest that first-parity records should preferably be used for genetic evaluation of bulls for calving performance. In such routine evaluations both stillbirth and calving difficulty, and both direct and maternal effects, should be included.

Animals↗

PubMed2003

Effect of incomplete pedigrees on estimates of inbreeding and inbreeding depression for days to first service and summit milk yield in Holsteins and Jerseys.

A method to measure completeness of pedigree information is applied to populations of Holstein (registered and grade) and Jersey (largely registered) cows. Inbreeding coefficients where missing ancestors make no contribution were compared to a method using average relationships for missing ancestors. Estimated inbreeding depression was from an animal model that simultaneously adjusted for breeding values. Inbreeding and its standard deviation increased with more information, from 0.04 +/- 0.84 to 1.65 +/- 2.05 and 2.06 +/- 2.22 for grade Holsteins with <31%, 31 to 70%, and 71 to 100% complete five-generation pedigrees. Inbreeding from the method of average relationships for missing ancestors was 2.75 +/- 1.06, 3.10 +/- 2.21, and 2.89 +/- 2.37 for the same groups. Pedigrees of registered Holsteins and Jerseys were over 97% and over 89% complete, respectively. Inbreeding depression in days to first service and summit milk yield was estimated from both methods. Inbreeding depression for days to first service was not consistently significant for grade Holsteins and ranged from -0.37 d/1% increase in inbreeding (grade Holstein pedigrees <31% complete) to 0.15 d for grade Holstein pedigrees >70% complete. Estimates were similar for both methods. Inbreeding depression for registered Holsteins and Jerseys were positive (undesirable) but not significant for days to first service. Inbreeding depressed summit milk yield significantly in all groups by both methods. Summit milk yield declined by -0.12 to -0.06 kg/d per 1% increase in inbreeding in Holsteins and by -0.08 kg/1% increase in inbreeding in Jerseys. Pedigrees of grade animals are frequently incomplete and can yield misleading estimates of inbreeding depression. This problem is not overcome by inserting average relationships for missing ancestors in calculation of inbreeding coefficients.

Animals↗

PubMed2004

Genetic and phenotypic correlations between milk coagulation properties, milk production traits, somatic cell count, casein content, and pH of milk.

Genetic and phenotypic correlations between milk coagulation properties (MCP: coagulation time and curd firmness), milk yield, fat content, protein content, ln(somatic cell count) (SCS), casein content, and pH of milk and heritability of these traits were estimated from data consisting of milk samples of 4664 Finnish Ayrshire cows sired by 91 bulls. In addition, differences in average estimated breeding values (EBV) for the above traits between the cows with noncoagulating (NC) milk and those with milk that coagulated (CO samples) were examined. The estimations were carried out to study the possibilities of indirect genetic improvement of MCP by use of the above characteristics. The genetic and phenotypic correlations between MCP and the milk production traits were low or negligible. The genetic associations between desirable MCP and low SCS were rather strong (-0.45 to 0.29). Desirable MCP correlated both genetically and phenotypically with low pH of milk (-0.51 to 0.50). The rather high heritability estimates for curd firmness in different forms (0.22 to 0.39), and the wide variation in the proportion of daughters producing NC milk between the sires (0 to 47%) suggested that noncoagulation of milk is partly caused by additive genetic factors. Based on the genetic correlations between curd firmness and SCS and the high EBV for SCS obtained for the cows with NC-milk, it is possible that the loci causing noncoagulation of milk and increasing somatic cell count of milk are closely linked or partly the same. One means to genetically improve MCP and to reduce the occurrence of NC milk could thus be selection for low somatic cell count of milk.

Animals↗

PubMed1981

Periparturient endocrine changes of conceptus and maternal units in Jersey cows bred for milk yield.

Control cows, sired by and bred to bulls with assumed zero estimated breeding values, and selected cows, sired by and bred to bulls of high predicted difference for milk yield, were used. Blood samples were collected via jugular venipuncture on alternate days from 35 to 14 days prepartum, from 14 to 28 days postpartum, and daily from 14 days prepartum to 14 days postpartum. We examined blood hematocrit, and concentrations in plasma of protein, estrone, estradiol, estrone sulfate, progestins, glucocorticoids, luteinizing hormone, and prolactin. Total plasma volume was measured on days -21, -7, and +11. Weekly body weights, prepartum and postpartum, were recorded. All data were analyzed by least squares analysis of variance with day and hematocrit as continuous independent variables. Hematocrit was higher for selected cows throughout the sampling period. Prepartum concentrations of progesterone were higher in selected cows, but concentrations of estrone, luteinizing hormone, and prolactin were lower than in control cows. Hormonal and physiological responses indicated that selection for milk yield influenced both the conceptus and maternal units as measured by prepartum endocrine function.

Animals↗

PubMed1981

Periparturient and postpartum endocrine changes of conceptus and maternal units in Jersey cows bred for milk yield.

Control cows, sired and bred by bulls of zero estimated breeding value, and selected cows, sired by and bred to bulls of high predicted differences for milk yield, were used to evaluate maternal endocrine changes from 14 days prepartum to 28 days postpartum. Examined were concentrations in plasma of 13, 14 dihydro-15 keto-prostaglandinF2 alpha, progesterone, estrone sulfate, estrone, luteinizing hormone, and prolactin. Ability of cows to release prolactin and luteinizing hormone on day 10 postpartum was evaluated after a simultaneous injection of thyrotropin releasing hormone (100 microgram) and gonadotropin releasing hormone (100 microgram). Changes in progesterone and estrogens prepartum lead to peak concentrations of prolactin and prostaglandin at parturition and 3 days postpartum, respectively. Higher basal concentrations of prolactin for control cows prepartum were associated with a higher prolactin release by thyrotropin releasing hormone at 10 days postpartum. Although release of luteinizing hormone in response to gonadotropin releasing hormone did not differ between groups on day 10 postpartum, a subsequent increase in progesterone to above 1 ng/ml was earlier and more precisely synchronized among control cows (16 +/- .43 versus 23 +/- 2.33 days). Within cow concentrations of F2 alpha 13, 14 dihydro-15-keto-prostaglandin-F2 alpha were correlated with size of previous gravid uterine horn (.67) and milk yield (-.39). Selection for milk yield influenced postpartum endocrine function.

Animals↗

PubMed1983

Factors affecting performance of Nili-Ravi buffaloes in Pakistan.

Effects of herd, year, age, season, and lactation length on milk yield and reproductive efficiency for the Nili-Ravi breed of buffalo were determined by analysis of variance of 5,716 lactation records from two herds in Pakistan. Herds differed in all traits. Herd average milk yields were 1,702 and 2,064 kg. Year, season, herd, parity number, days in milk, days open, age, and sire all influenced milk yield. Herd, year, season, and parity number also had significant effects on days open and calving interval. Month of calving was important for time until return to estrus. Percentages of variance in milk yield attributed to herd, year, sire, cow, and residual were 20.3, 11.4, 4.3, 17.0, and 47.0. Classification of lactation length (greater than 60, greater than 250, or at least 305 days) markedly influenced the sire component of variance suggesting some interdependence of milk yield and lactation length. Total variance for milk yield was 466,911 kg2. Within herd heritability for milk yield was .25, and repeatability was low (.31). Predicted breeding values for sires for 250 to 305-day milk ranged from -172 kg to +260. Cows in Herd 1 completed 5.58 lactations with an average herd life of 12.3 yr; Herd 2 cows completed 4.52 lactations with culling at 10.6 yr. Frequency of termination of lactations because of mastitis, reproductive problems, or health was similar to frequencies for cattle. Factors affecting milk yield in buffaloes are similar to those of cattle.

Age Factors↗

PubMed1988

Factors affecting length of herdlife in purebred and crossbred dairy cattle.

The proportional hazards model with censoring was used to assess the effects of breeding value, disease, calving, size, and udder and lactation traits on length of herdlife of 3881 heifers in five herds. Data were recorded over 10 yr from three lines: a Holstein line, an Ayrshire-based line, and a crossbred line. Influences on survival were assessed from data collected at birth, 34, 50, and 82 wk, first freshening, and at 112 and 308 d postpartum. Median estimated herdlife (age at 50% culling) was 3.9 yr for animals alive at first freshening and increased to 4.3 yr for those that completed a first lactation (308 d postpartum). Herds differed greatly in the pattern of culling after freshening. Crossbred females had 21 wk longer median estimated herdlife than the mean of the purelines at 308 d postpartum. Individual milk yield was positively associated with longevity and had the greatest impact on length of herdlife. Abortion and fertility measured as days to last insemination were negatively associated with length of herdlife. Large heifers tended to have increased longevity. High feed intake postpartum was associated with reduced length of herdlife. Objective measures of conformation, which included measurements of the udder, were not important in determining herdlife.

Animals↗

PubMed1991

Method and effect of adjustment for heterogeneous variance.

Lactation records were standardized for differing genetic and error variances across herds and over time based on phenotypic variance for each herd-year-parity group. Each herd-year-parity phenotypic variance estimate was combined with those of adjacent years and regressed toward a region-year-parity variance. Heritability was assumed to be .25 at mean variance within year and to range from .2 for herds with smallest phenotypic SD to .3 for herds with largest phenotypic SD. Lactation deviations from management group mean were adjusted by ratio of base genetic SD to genetic SD estimated from heritability and phenotypic SD. The base was defined as 1987 calvings for first parity and 1988 calvings for later parities. Records were weighted according to heritability by multiplying lactation length weight by herd error weight defined as ratio of base error variance to error variance in the adjusted record. Estimated genetic trend for milk increased by nearly 5 kg/yr for Holsteins with this adjustment, which caused predicted breeding values of oldest animals to be lower by about 100 kg. Most correlations of parent and progeny information were slightly higher with adjusted data. Cows in high variance herds were most likely to have large reductions in their evaluations. Adjustment for heterogeneous variance was implemented in July 1991 for national evaluations for yield traits.

Animals↗

PubMed1992

Analysis of levels of inbreeding and inbreeding depression in Jersey cattle.

A pedigree file of 157,015 male and female Jersey cattle (born after 1955) from the Canadian herdbooks was investigated for the occurrence of inbreeding. A large proportion of Jersey bulls and cows were inbred (32.4 and 36.3% for bulls and cows, respectively). However, average inbreeding coefficients of these inbred cows and of all cows were low. First lactation milk, fat, and fat percentage records for 53,592 Jersey cows were analyzed. Inbreeding was included in the animal model as a linear covariate. The regression coefficients of milk, fat, and fat percentage on inbreeding were -9.84 kg, -.55 kg, and -.0011% per 1% increase of inbreeding. Inbreeding depression was not enough to cause large reductions of milk and fat yield of a cow with average inbreeding. However, when the inbreeding coefficient was greater than 12.5%, the inbreeding depression was significantly higher than expected and such that intentional inbreeding is not justified unless the mating is to an animal with exceptionally high breeding value.

Algorithms↗

PubMed1992

Estimation of heterogeneous within-herd variance components using empirical Bayes methods: a simulation study.

Genetic evaluation using BLUP can accommodate heterogeneous variances if the necessary variance components are known; this may require estimation of variance components within each heterogeneous subclass. Properties of sire and residual variance estimates obtained by an empirical Bayes approach, which combines within-herd and prior estimates, were examined via simulation. Prior estimates were obtained using REML across herds, as if variances were homogeneous. Convergence was improved by incorporation of prior information such that variance component estimates could be obtained in within-herd situations for which a REML algorithm failed to converge. Accuracy of sire variance estimates was greatest when both within-herd and prior information were used, but improvement in accuracy of residual variance estimates associated with incorporation of prior information was minimal. Correlations between sires' standardized true transmitting abilities and PTA that used empirical Bayes variance estimates were larger than those obtained when heterogeneity was ignored. Proportions of sires selected, based on standardized PTA, from environments with differing genetic and residual variances became more uniform as the relative weight placed on within-herd data in variance estimation increased. Thus, useful variance component estimates can be obtained within individual herds by using empirical Bayes methods with across-herd estimates as prior information; this may allow prediction of breeding values that are less influenced by heterogeneous variances.

Algorithms↗