GWAS analysis for tolerance to heat stress and milk production, in subtropical Egyptian goats

The conservation of local Egyptian goat genotypes has been a national program since 2009. Our study investigated different subtropical Egyptian goat populations (367 does) from different harsh ecological zones(hot Upper Egypt, Coastal Zone of Western Desert, and Wahati Desert Oasis) to identify genes associated with heat stress. We examined the physiological response of animals that were exposed to simulated summer grazing conditions, and physiological parameters including respiration rate, gas volume, rectal temperature, and skin temperature. Temperature Humidity Index ranged from 98.6 to 109.3, indicating that the animals were under severe heat stress. Results showed significant differences between the populations in their tolerance to heat stress, with Saidi goats being the most adapted to hot-dry conditions. Respiration rate was found to be the most reliable physiological trait for differentiating between animals in their tolerance to heat stress. The GWAS analysis involved 157 genotypes and 54,032 marker-SNPs, revealing 90 SNPs associated with heat stress and 70 SNPs associated with milk production. Chromosome 1 had the highest number of SNPs associated with heat-stress traits, while chromosome 4 exhibited the largest number of significant SNPs associated with milk production. Several genes were associated with heat stress response and tolerance in goats. These genes were categorized into three main groups: heat stress response, stress response, and reproduction, and feed intake. The first group includes USP54, KDM6A, and ETNPPL, which have multiple functions, such as steroid biosynthesis, metabolism, and stress response, and are also involved in key biological processes such as reproduction, immune response, and metabolism. The second group, which is mostly associated with immune response, includes GLTSCR2 and NAALADL2. Finally, a group of genes that may control animal feed intakes, including TRPM3 and ZBTB8A. Additionally, several genes, such as FHIT, GALNT18, RAPGEF5, and RBFOX1, linked to milk production, are known to be linked fertility, and fatty acid composition. These findings provide insights into the potential roles of these genes in heat stress response and tolerance in goats, and the genetic basis for improved milk production and animal welfare and can be used as selection markers in the ongoing breeding programs.