PS11-1. Effect of Heat Stress on the Transcriptome of Lambs During the Weaning Period.

Abstract This study investigated the impact of heat stress on the transcriptomic profile of Florida Cracker lambs. Twenty-four lambs were randomly assigned to either a heat stress (HT; n = 12) or cooling (CTL; n = 12) group for six weeks. HT lambs were exposed to natural summer temperatures, while CTL individuals had access to an evaporative cooling fan. Ambient temperature and humidity were recorded weekly to calculate the Temperature-Humidity Index (THI). Blood samples were collected via jugular venipuncture at weeks 1, 4, 8, and 12, and stabilized using RNAprotect tubes. Total RNA was extracted with the RNeasy Protect Animal Blood Kit (Qiagen), and libraries were prepared using the KAPA RNA HyperPrep Kit with RiboErase Globin Reduction (Roche). Sequencing was performed on the Illumina NovaSeq 6000 platform. Quality filtering of FASTQ files was done using FastQC, and differential gene expression analysis was conducted with DESeq2. Genes with a false discovery rate (FDR) ≤ 0.05 were considered differentially expressed (DEGs). Functional enrichment of DEGs was performed using SR-plot. Comparative analysis revealed 2 DEGs (ADGRA1 and ATP10A) at week 1, and 14 DEGs at week 12 (CDC42EP2, LY6G5B, POGLUT1, ALOX15, QTRT2, SLC16A1, CHD4, NUDT12, PABPN1, ENSBTAG00000046372, PER1, ZNF821, ZFPM1, and GTF2H3). Week 1 DEGs were linked thermogenesis and energy expenditure; week 12 to metabolism, cell cycle and chromatin structure. Our results evidence the ability of Florida Cracker sheep to adapt to heat stress in the summer season. Further studies are needed to understand these molecular mechanisms affected by heat stress in sheep.