Dairy Cattle Reproduction, Production, and Disease Resistance in the Omics Era: Genome-Wide Selection Signatures Identify Candidate Genes in Sahiwal Cattle.

Climate emergency and ecological sustainability call for new ways of thinking livestock health, including the dairy cattle. This study unpacks the genetic diversity and selection sweeps of Sahiwal cattle in relation to adaptability, production, and disease resistance. Using nucleotide diversity (π) calculated from 10 kb windows across the genome with VCFtools, 716 regions of genetic diversity were identified across 29 chromosomes, and importantly, with chromosome 15 showing the highest density. A total of 92 quantitative trait loci (QTL) linked genes were analyzed, with chromosome 1 harboring the highest number. Trait association analysis using the Cattle QTL database showed that 14 genes were linked to production traits, 10 to reproduction traits, and 8 to disease susceptibility. Notable genes included and , which influence milk production traits such as fat percentage and yield, and and , which affect reproductive traits. Additionally, the genes and were associated with disease traits such as bovine respiratory disease and sole ulcers. Selection sweeps, identified using Tajima's D, revealed 728 sweeps across the genome, with chromosomes 6 and 8 showing the highest frequencies. These sweeps indicate regions under strong selective pressure, likely due to the breed's adaptation to arid environments and specific trait selection. The present study highlights how genetic diversity and selection sweeps contribute to Sahiwal cattle's adaptability, production efficiency, and disease resistance. The insights reported here provide a foundation for livestock health and targeted breeding strategies in the case of Sahiwal cattle under diverse ecological conditions such as tropical climate.