Impact of sperm hyperactivation and estrus on pregnancy in timed AI Bos indicus beef cows
DOI:
https://doi.org/10.11606/issn.1678-4456.bjvras.2025.223638Keywords:
Estrus, Sperm hyper-activation, OvulationAbstract
This study hypothesized that cows that express estrus within 48 hr of progesterone insert removal ovulate earlier, and that the association between estrus and the degree of sperm hyperactivation increases pregnancy rates in beef cows. In Experiment 1, Nelore cows were divided into two groups according to the expression of estrus within 48 hr after progesterone removal: Estrus (E48, n = 19) and No Estrus (NE48, n = 13). Cows from the E48 group ovulated earlier (P < 0.02; 73.3 ± 13.1 h vs. 95.5 ± 37.5 h). In Experiment 2, 480 postpartum beef cows were treated as described in Experiment 1. The semen from the two bulls used for timed artificial insemination was classified as Hyper-activated (H+) and Non-Hyper-activated (H-). The batches of H+ and H- semen of each bull used to inseminate cows were distributed in E48 and NE48 cows. The pregnancy per AI of cows from the E48H+ (60.7%, 91/150) and E48H- (65.7%, 88/134) groups was greater (P < 0.02) compared with cows from NE48H+ (51.6%, 66/128) and NE48H- (41.2%, 28/68) groups. Cows that exhibited estrus ovulated earlier and had higher pregnancy rates. The kinematics of the semen used in this study did not influence the fertility of cows, regardless of estrus incidence.
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