Breeding Values For Milk Yield Research Articles

Estimação de parâmetros genéticos utilizando-se a produção de leite no dia do controle em primeiras lactações de vacas da raça Jersey

Registros da produção de leite de 3.531 controles de 620 primíparas da raça Jersey foram utilizados para a estimação dos componentes de covariância e dos parâmetros genéticos para a produção de leite por meio dos modelos de repetibilidade e de regressão aleatória. O modelo de repetibilidade (MR) incluiu os efeitos fixos de rebanho-ano-mês do controle, estação do parto e idade da vaca ao parto como covariável, com termos linear e quadrático, e os efeitos aleatórios de animal, de ambiente permanente e residual. O modelo de regressão aleatória incluiu os mesmos efeitos do MR, com o uso da função de Wilmink para a modelagem dos efeitos fixo (estação de parto) e aleatórios (genético de animal e de ambiente permanente). As estimativas de variância genética aditiva, de ambiente permanente, residual e fenotípica, e de herdabilidade e repetibilidade para a produção de leite usando-se o MR foram, respectivamente, 7,08; 1,88; 7,79 e 16,76 kg² e 0,42 e 0,50. Pelo modelo de regressão aleatória, os valores de herdabilidade para a produção de leite decresceram de 0,81 a 0,20 ao longo da lactação. As estimativas de variância genética aditiva mantiveram-se praticamente constantes durante a lactação, com maiores valores no início e final da lactação. As correlações genéticas foram próximas à unidade para as produções de leite da fase intermediária da lactação e diminuíram com o aumento do período entre os controles leiteiros. O modelo de repetibilidade não é a melhor alternativa para a modelagem das produções de leite no dia do controle da primeira lactação de vacas Jersey no Brasil.

Milk protein genes CSN1S1, CSN2, CSN3, LGB and their relation to genetic values of milk production parameters in Czech Fleckvieh

Genotypes of milk protein genes, alpha<sub>S1</sub>-casein (CSN1S1), beta-casein (CSN2), kappa-casein (CSN3) and beta-lactoglobulin (LGB), were detected in 440 individuals of Czech Fleckvieh breed using a PCR-RFLP method. Breeding values of genotyped animals were obtained from the Official Database of Progeny Testing. A granddaughter design including 5 grandsires, 33 sons and 402 granddaughters was used for evaluation. Statistical analysis was carried out in SAS program using a restricted maximum likelihood method (REML). The aim of this study was to determine allele and genotype frequencies of observed genes and to find the relation between genotypes of genes and milk production parameters expressed by the breeding values of animals. The positive findings of frequencies of CSN3 allele B (0.38) and genotype BB (13%) were detected in the observed population. Significant differences were found between genotypes of loci CSN1S1, CSN2 and CSN3 and breeding values for milk production parameters. Genotypes of LGB locus were not significantly related to any of the milk production parameters. Significant effects were found between CSN1S1 locus and average breeding value for milk yield, CSN2 locus and breeding values for all parameters except for protein content and CSN3 locus and breeding values for protein content and protein yield. These findings contribute to a better understanding of the genetic constitution of Czech Fleckvieh breed and help with the application of the information to breeding.    

Avaliação genética de caprinos da raça Alpina utilizando-se a produção de leite no dia do controle

Com os objetivos de estimar os parâmetros genéticos e predizer os valores genéticos para produção de leite no dia do controle (PLDC) e para produção acumulada (PAC), utilizaram-se dados de 356 cabras da raça Alpina, com 825 lactações e 26.389 controles semanais efetuados entre os anos de 1997 e 2004. A PLDC foi analisada considerando-se o efeito fixo de grupo contemporâneo (ano-mês de controle), a idade da cabra ao parto, como covariável, e os efeitos aleatórios genético aditivo e de ambiente permanente. Para PAC, o modelo incluiu os mesmos efeitos aleatórios, o efeito fixo de grupo contemporâneo (ano-mês de parto) e as covariáveis idade da cabra ao parto e duração da lactação. Em geral, as herdabilidades estimadas foram de maiores magnitudes na primeira lactação, nos controles intermediários, indicando possibilidade de resposta à seleção. As correlações de ordem entre os valores genéticos para a produção até 305 dias de lactação e as PLDC intermediárias foram maiores que as do início e do final da lactação. Apesar de a correlação de ordem ter sido alta, houve alterações na classificação dos reprodutores para produção até 305 dias de lactação quando a seleção foi praticada com base na PLDC aos 90 dias. A seleção pela PLDC e PAC no meio da lactação pode ser indicada como critério de seleção, em substituição à produção até 305 dias.

Relation between Holstein bulls’ proofs for milk in USA and the milk yield, age at first calving, calving interval and survival to third calving of their F1 zebu progeny in Venezuela

SummaryTo determine the effect of USA Holstein bulls’ breeding value for milk yield on the performance of their female F1 progeny in the lowland tropics of Venezuela, semen was chosen from 39 sires, representing bulls with the highest (class H, n = 21) or average (class A, n = 18) proofs for milk, available locally. The mean proofs of the H and A sires were 937 and 237 kg milk, respectively, when semen was purchased in 1989–93, and 212 and −386 kg when updated in 2001. Progeny from commercial zebu dams were kept grazing on three dual purpose farms, where herd average milk yields were 735, 1113 and 3524 kg per lactation. Records on milk yield, lactation length, calving interval, age at first calving and survival rate to first, second and third calving from 222 progeny (476 lactations) were analysed using mixed linear models. The effect of sire class approached significance (p = 0.07) for milk yield and survival rate to second calving, with H daughters superior to A progeny by 41 and 46%, respectively, and no significant disadvantage for any trait. Class × farm interaction was only significant for age at first calving. Rank correlations using USA proofs for milk and the adjusted mean values for bulls with =15 F1 records were 0.72 (p < 0.01, milk yield) and −0.07 (calving interval). Differences between sires, within classes, were highly significant for age at first calving and calving interval. It was concluded that the use of Holstein bulls with high USA milk proofs is probably justified for producing F1 daughters, but that evaluation for growth rate and daughter fertility under tropical grazing conditions may be advisable.

Single and multitrait estimates of breeding values for survival using sire and animal models

AbstractSurvival data were simulated under the Weibull model in a half-sib family design, and about 50% of the records were censored. The data were analysed using the proportional hazard model (PHM) and, after transformation to survival scores, using a linear and a binary (logit) model (LIN and BIN, respectively), where the survival scores are indicators of survival during time period t given survival up to period t – 1. Correlations between estimated and true breeding values of sires (accuracies of selection) were very similar for all three models (differences were smaller than 0·3%). Daughter effects were however less accurately predicted by the LIN model, i.e.taking proper account of the distribution of the survival data yields more accurate predictions of daughter effects. The estimated variance components and regressions of true on estimated breeding values were difficult to compare for the LIN models, because estimated breeding values were expressed as additive effects on survival scores while the simulated true breeding values were expressed on the underlying scale. Also the differences in accuracy of selection between sire and animal model breeding value estimates were small, probably due to the half-sib family design of the data. To estimate breeding values for functional survival, i.e. the component of survival that is genetically independent of production (here milk yield), two methods were compared: (i) breeding values were predicted by a single-trait linear model with a phenotypic regression on milk yield; and (ii) breeding values were predicted by a two-trait linear model for survival and milk yield, and breeding values for survival corrected for milk yield were obtained by a genetic regression on the milk yield breeding value estimates. Both methods yielded very similar accuracies of selection for functional survival, and are expected to be equivalent.

The relationship between Holstein bull breeding values for milk yield derived in both the UK and Kenya

The international trade in semen has resulted in the widespread use of Holstein genes for dairy production in tropical countries. Breeders in the tropics have access to bull breeding values derived in the exporting countries but rarely to those derived in their own country. This study was designed to investigate the relationship between bull breeding values in both Kenya and UK for milk production and to estimate the magnitude of any genotype by environment interaction for milk production that may exist between the two countries. Milk production data from 3185 Kenyan and 43 056 UK lactations were analysed, the UK data being selected from herds containing daughters of bulls also used in Kenya. There was a difference in genetic variance for milk yield between the two countries, with the heritability for first lactation 305-day milk yield being 0.45±0.02 in UK and 0.26±0.06 in Kenya. The genetic correlation between first lactation milk yield in the two countries was 0.49±0.06, implying a genotype by environment interaction in milk yield. The relative rate of response in Kenyan milk yield based on UK breeding values was estimated to be 44% of the rate expected in the UK. Although the use of UK breeding values will lead to an improvement in milk yield in Kenya there are some bulls whose daughters produce better in Kenya than their UK breeding values would imply. From the present study breeding values (BV) derived in the UK could be converted for use in Kenya using the formula −68.8+0.887(UK BV).

Genetics of milk yield and fertility traits in Holstein-Friesian cattle on large-scale Kenyan farms.

Purebred Holstein-Friesian cows are the main exotic breed used for milk production on large, medium, and small farms in Kenya. A study was undertaken on seven large-scale farms to investigate the genetic trends for milk production and fertility traits between 1986 and 1997 and the genetic relationships between the traits. This involved 3,185 records from 1,614 cows, the daughters of 253 sires. There was a positive trend in breeding value for 305-d milk yield of 12.9 kg/ yr and a drop in calving interval of 0.9 d/yr over the 11-yr period. Bulls from the United States (U.S.) had an average total milk yield breeding value 230 kg higher than the mean of all bulls used; Canada (+121 kg), Holland (+15 kg), the United Kingdom (U.K., 0 kg), and Kenya (-71 kg) were the other major suppliers of bulls. Average breeding values of bulls for calving interval by country of origin were -1.31 (Canada), -1.27 (Holland), -0.83 (U.S.), -0.63 (Kenya), and 0.68 d (U.K.). The genetic parameters for 305-d milk yield were 0.29 (heritability), 0.05 (permanent environment effect as proportion of phenotypic variance) resulting in an estimated repeatability of 0.34. Using complete lactation data rather than 305-d milk yield resulted in similar estimates of the genetic parameters. However, when lactation length was used as a covariate heritability was reduced to 0.25 and the permanent environment effect proportion increased to 0.09. There was little genetic control of either lactation length (heritability, 0.09) or calving interval (heritability, 0.05); however, there were strong genetic correlations between first lactation milk yield, calving interval, and age at first calving.

Relationships of growth hormone gene and milk protein polymorphisms to milk production traits in Simmental cattle.

The importance of milk proteins and the positive effect of administration of growth hormone (GH) on milk production, and the presence in some dairy cattle lines of greater GH concentrations prompted us to examine the presence of restriction fragment length polymorphism at the GH gene using the restriction enzyme TaqI and to investigate associations between this polymorphism in Simmental cows and bulls, as well as milk protein variants in Simmental cows, and milk production traits. Blood and milk were sampled from 279 Italian Simmental cows and semen was collected from 148 bulls of the same breed. Two fragment bands, denoted A and B, of 6200 and 5200 bp respectively, were examined and three patterns, AA, AB and BB, were found in both animal samples. All variants previously reported in other studies, for kappa, beta, and alpha s1-caseins, and beta-lactoglobulin, were found in the cows' samples. For the cows' samples, a BLUP (Best Linear Unbiased Predictor) analysis of results was performed using a REML (Restricted Maximum Likelihood) program and known heritabilities, whereas for bulls we have performed a General Linear Model analysis. The effect of GH gene polymorphism, using TaqI restriction enzyme, on milk production traits was not significant, but bulls of BB pattern had a higher breeding value for milk yield than AA bulls (P < 0.05). For the kappa-casein genotypic effects, cows of AB genotype gave milk with 1.53 +/- 0.70 g/kg less fat than cows of AA genotype. In addition, breeding values for milk protein content were significantly higher in BB bulls, with 0.87 +/- 0.32 and 0.71 +/- 0.34 g/kg more milk protein than AA and AB bulls respectively. Thus, our results revealed a GH gene polymorphism and indicated significant effects of milk protein polymorphisms on milk production traits in the Italian Simmental breed.

Associations of Bovine Lymphocyte Antigens with Milk and Meat Production Traits of Norwegian Cattle

Bovine lymphocyte antigens of class I were defined for 434 AI bulls of Norwegian Cattle, which is a dual purpose breed. The antigens w16, A2, and A8 occurred at highest frequencies. A gene substitution model was used to compare bovine lymphocyte antigens with total breeding value and breeding values for milk yield, milk fat percentage, milk protein percentage, and meat production. Several bovine lymphocyte antigens were significantly associated with the traits in question: low fat percentage was associated with A8, A10(w50), and A11; high milk protein percentage with A13; and low meat production with the rare antigen w1. Associations of the bovine lymphocyte antigens and milk yield were not significant.

A note on relations between oral stereotypies in dairy cows and milk production, health and age

The relationships of oral stereotypies to milk production and health were investigated in 95 dairy cows that had completed between one and five lactations. Forty cows in the herd performed stereotypies, mainly tongue-rolling and to a lesser extent bar-biting. A significant positive relation was found between the dependent variable milk production and stereotypies (P &lt; 0·05) according to a GLM-model also containing lactation group (age; P &lt; 0·01), sire (breeding value for milk yield; P &lt; 0·01), and health I ailments (P &gt; 0·05). There was no correlation between different phases in lactation and the frequency of stereotypies (Spearman correlation coefficient = 0·124; no. = 0·40; P &gt; 0·05).

Physiological attributes of male and juvenile cattle differing in genetic merit for milk yield: A review

Experiments to identify physiological attributes of immature cattle that are correlated with breeding value for milk yield have been reviewed. From the results, the measurement of growth hormone and its secretion when challenged with secretagogues currently appear most promising. Although measurements of kinetic parameters associated with thyroid hormones have given positive results, further study has been inhibited by the need to use radioisotopes and by perceived associations with metabolic rate. Measurements of metabolites and insulin under a range of conditions have, in general, not been of significance or, where initial results were encouraging, have proven not to be repeatable. It was concluded that future experimentation must be on a larger scale than has previously been the case and this would best be achieved through international collaboration.

Associations between blood groups, blood protein polymorphisms and breeding values for production traits in Swedish Red and White Dairy bulls

The relationships of nine blood group systems and two blood protein polymorphisms with breeding values for several production traits were examined in dairy cattle of the Swedish Red and White (SRB) breed. The material consisted of 2212 bulls; the bulls were performance tested for growth rate and their breeding values for milk yield, fat and protein content in milk were estimated from progeny tests. The direct effect of marker alleles or marker phenotypes was analysed in a multiple regression model. Several significant associations were found; many supported earlier findings. However, the contribution of the markers to the total variation of the breeding values was very small. Linkage between marker loci and production loci was studied in offspring from heterozygous sires by estimating the interactions between sire and marker alle using a model eliminating the direct effects of sire and marker alle. There were strong indications of linkage between some marker loci (e.g. B, J and Am-1 loci) and loci with large effects on production traits.

Genetic Relationships and Additive Genetic Variation of Productive and Reproductive Traits in Guernsey Dairy Cattle ,

Data were first lactation production and reproduction records initiated from 1958 to 1981 in two experiment station Guernsey herds. Heritability estimates using paternal half sib groups were .24±.12 for milk yield, .27±.12 for fat yield, and .77±.15 for fat percentage. Heritability estimates for reproductive traits ranged from .01 to .04 for number of services, service period, conception rate, and days open, but were higher for days in milk at first breeding (.12) and age at first calving (.13). Except for age at first calving, coefficients of additive genetic variation were larger for reproductive traits than for productive traits. Genetic correlations between measures of production and reproduction were moderate to large and antagonistic, except that the relationship between production and age at first calving was favorable. Breeding value estimates for milk yield and reproduction were negatively correlated for sires with above average breeding values for milk yield. Huge phenotypic variances for reproductive traits masked substantial additive genetic variation for these traits. When all things are considered it seems unwise to ignore reproductive performance in selection programs for dairy cattle.

Relationship between blood attributes and predicted breeding value for milk yield in calves

Relationship between blood attributes and predicted breeding value for milk yield in calves

Effects of Sire of Fetus upon Subsequent Production and Days Open of the Dam

To quantify effects of the fetal-placental unit upon postpartum performance of the dairy cow, Dairy Herd Improvement Association records from Florida, Georgia, North Carolina, and South Carolina (27,200 lactations of 11,935 Holsteins and 3,731 of 1788 Jerseys) were studied by method of least squares. The final model included herd-year-season, sire of fetus, and sire of cow. Sire of fetus accounted for 8.2 and 11.8% of the total variability in mature equivalent milk yield (Holsteins and Jerseys), 9.8 and 14.3% in fat yield, and 1.9 to 3.2% in days open. Interactions of sire of fetus with sire of cow accounted for none of the variability in yields (negative estimates of variance) but 4.4 and 4.8% of the variability in days open. Correlations between effects of sire of fetus on milk and fat yields were .96; for yields and days open they were .02 and −.02 for Jerseys and −.12 and −.13 for Holsteins. Correlation between sire of fetus constants and estimated breeding values for milk yield in a sample of 50 Jersey sires was −.04. Future consideration of sire of fetus effects could lead to increased repeatability of sire proofs and rate of genetic change. Hypothesized mechanism is that effects of the fetal-placental unit, possibly hormonal and at least partly genetically determined, influence development of the dam's mammary gland and its subsequent performance.