Evaluation of Breeding Values and Variance Components of Birth and Weaning Weights in the Holstein Cows Herd Based on...

Birth weights, weaning, and daily weight gain of calves before weaning vary according to farm animals' environment, production, and breeding systems. It is expected that these traits will be affected by direct genetic influences and the genetic effects of the mother. Therefore, this study was designed and conducted on 50 Holstein cows herds to estimate breeding value (after estimating the mean of allele effect and the mean of allele replacement effect of the DRB3 gene), as well as the variance components of the birth and weaning weight traits, depending on the variance resulting from the inherited polymorphism of the DBR3 gene. The results of this study showed a preference for the wild allele A based on its mutant counterpart B was the mean allele-effect value and the mean allele substitution value, corresponding to the preference for the A allele in both traits, the individuals with the AA genotype outperformed the homozygotes and mutants in the educational value (a value that is estimated based on what the individuals carry from the genotypes). The genetic variance of weaning weight was higher than the genetic variance of birth weight, and this may be due to the preference of allele A and the AA structure over the other two components in positively affecting birth and weaning weights, indicating the importance of this genetic structure of the DBR3 gene in selection within the genetic improvement programs for the color characteristic of Holstein cows.