GENETIC IMPROVEMENT STRATEGIES FOR ENHANCING MILK PRODUCTION IN DAIRY CATTLE

Abstract

The current experiment was carried out to assess the effectiveness of genomic selection in maximizing milk output and functional characteristics in milk-producing cows, particularly the dilemma of the size of the reference population, the heritability of a trait, and the cost of genotyping. A 4,500- Holstein and Jersey cows population was stratified into a reference and a validation population, high-density genotyping of the reference population and low-density genotyping of the validation population followed by high-density coverage imputation. GBLUP and Bayesian mixture models estimated the breeding values genomic and compared them with the traditional pedigree-based BLUP. Genomic selection enhanced prediction accuracy by about forty to sixty-five percent, with the biggest improvements noted in low-heritability traits like daughter pregnancy rate and longevity. The annual genetic gain increased more than twice on production traits and thrice on fertility traits with the highest rates obtained when functional annotations were included. Low-density chip imputation was found to have concordance rates of 0.96 with a reference population of 3,000 animals, approximately eighty percent of the genotyping costs. The average generation intervals decreased by nearly sixty-nine percent to 1.9 years. Significant quantitative trait loci such as DGAT1, which accounted more than eighteen percent of the fat yield variance, GHR, and CSN1S1 were confirmed as key contributors to production traits. Imputation concordance of 10,000 animals in multi-breed panels reached over 0.98 in common single nucleotide polymorphisms with 0.81 in rare ones. The economic analysis showed net growth of more than four hundred and fifty eight thousand dollars per 1000 cows/year and payback period of more than two thousand four hundred percent in five years. These results prove that genomic selection is a revolutionary technology that will greatly accelerate the genetic advancement, decrease expenses, and boost the economic viability of the dairy breeding programs.