The effect of melatonin implants on the embryo yield and oxidative stress levels in superovulated Holstein heifers.

Superstimulation of ovaries predisposes the donors to oxidative stress, potentially impacting the outcomes. This study evaluated the effect of melatonin implants on embryo yield and oxidative stress levels in Holstein heifers, who were allocated to two groups: one (14 heifers) received melatonin implants (18 mg/50kg) before the start of superovulation, while the other (10 heifers) did not. Serum samples were collected on days 0, 9, and 16 to measure total antioxidant capacity (TAC) and total oxidant status (TOS). Ovarian follicles, corpora lutea, and recovered embryos were recorded at D16. Superovulation and Fertilization responses were not different; Ovulation response increased (80.73 ± 4.94 vs. 57.02 ± 10.61) in the treatment compared to the control. The mean number of CLs and Total recovered embryos were not different; Transferable embryos (3.85 ± 0.91 vs. 1.8 ± 0.37) were higher in treatment compared to the control (p˂0.05). Blastocysts and degenerated embryos were not different. TOS in the treatment group decreased at D7 and D16 compared with D0 (p˂0.05) but increased over time in control (p˂0.05); it was not different between groups at D0 but was lower in treatment than control at D9 and D16 (p˂0.05). TAC didn't change over time; however, it was higher in treated than in control donors at D7 (p˂0.05). OSI was lower in the treatment than control group at D9 and D16. Conclusively, melatonin implants in superovulated heifer donors increased the number of transferable embryos and reduced anovulated follicles, thereby enhancing ovulation and embryo quality. It mitigated oxidative stress by decreasing total oxidant status and boosting total antioxidant capacity.