Theriogenology. 2025 Dec 21;253:117790. doi: 10.1016/j.theriogenology.2025.117790. Online ahead of print.
ABSTRACT
This study aimed to evaluate the effects of heat stress (HS) on the follicular population at dominant follicle removal (DFR) and Ovum Pick-Up (OPU), oocyte quality and yields following OPU, and the subsequent in vitro embryo development in dairy cows. Ten Holstein cows were randomly assigned to either a heat stress challenge (HSC) or a control (CON) group (n = 5) in a split-plot crossover design with 2 periods. In Phase 1 (days 1-9), all the cows were fed ad libitum and were in thermoneutral conditions, and GnRH was given on Day 9. In Phase 2 (days 1-10), all cows were exposed to HSC using an electric heat blanket, while CON was pair-fed to HSC. On Day 7 (Phase 1), all the follicles were counted, and large follicles (>6 mm) were transvaginally aspirated (DFR). On Day 10, all the follicles were counted and transvaginally aspirated (OPU). After a 14-day washout period, the study was repeated (Period 2) and the environmental treatments were inverted relative to treatments from Phase 2 of Period 1, retrieved oocytes were graded (A, B, C, and D), and fertilized with frozen-thawed semen. Embryo development was evaluated on Days 3 and 7. An increased number of follicles was obtained 3 days after DFR in both HSC and CON groups (P
PMID:41442878 | DOI:10.1016/j.theriogenology.2025.117790