Danai Jattawa, Praew Thiengpimol, Thanathip Suwanasopee, Mauricio A Elzo, Skorn Koonawootrittriron
These findings underscore an urgent need for improved mastitis management, including routine bacterial screening, judicious antibiotic use and public health measures to mitigate transmission of resistant S. aureus to humans.
Improving the accuracy of genetic evaluation in smallholder dairy systems is essential for sustainable productivity. However, traditional polygenic models (PM) are often constrained by incomplete pedigree, heterogeneous management, and limited genotyping resources. This study evaluated a genomic-polygenic model (GPM) relative to a PM using data from a multibreed dairy population raised under Thai tropical smallholder conditions. Phenotypic records for 305-day milk yield (MY), fat percentage (FP), protein percentage (PP), and somatic cell count (SCC) from 14,417 first-lactation cows across 1,321 farms were analyzed together with genotypes from 5,479 animals generated using GeneSeek Genomic Profiler (GGP) arrays ranging from 9 K to 150 K SNPs. Both models included herd-year-season of calving, age at first calving, and heterosis as fixed effects, and additive genetic and residual components treated as random. The GPM yielded higher additive genetic variances and heritability estimates and produced more biologically consistent antagonistic correlations among traits than the PM. Prediction accuracy was improved for all animal groups under the GPM, with the largest gain observed in genotyped young sires (18.36%). Pedigree connectedness analysis indicated that genotyping animals with low to moderate relationships enhances accuracy cost-effectively. Despite persistent challenges associated with heterogeneous management and limited pedigree depth, the results demonstrate the practical value of genomic-polygenic evaluation for smallholder multibreed dairy populations in tropical environments.