Motility, oxidative status and morphology of frozen-thawed bovine semen are not impacted by fatty acid exposure in vitro.

While sperm migrate within the reproductive tract of cows experiencing negative energy balance (NEB), they come into contact with elevated concentrations of non-esterified fatty acids (NEFA). For this reason, this study aimed to investigate the effects of three different NEFA - palmitic acid (PA), stearic acid (SA), and oleic acid (OA) - on bovine sperm motility, kinetic parameters, oxidative status, and morphology. Frozen thawed semen samples from Bos taurus bulls were incubated with varying concentrations of each fatty acid, and the sperm's characteristics were analysed at different time points. Computer-Assisted Sperm Analysis (CASA) was employed to assess sperm motility and kinetic parameters. Concurrently, the production of the reactive oxygen species (ROS) and total antioxidant capacity were measured to determine the oxidative status. Additionally, sperm morphology was evaluated. In Experiment 1, different concentrations of PA did not show significant effects on total motility, progressive motility, or any kinetic parameters analysed. Similarly, PA did not have a significant impact on the oxidative status or sperm morphology. In Experiment 2, SA at various concentrations did not lead to significant changes in total motility, progressive motility, or any kinetic parameters evaluated. Furthermore, SA did not affect oxidative status or sperm morphology. In Experiment 3, the concentrations of OA used did not result in significant changes in total motility, progressive motility, or any kinetic parameters studied. Likewise, OA did not induce any alterations in oxidative status or sperm morphology. Overall, the results from all three experiments indicate that PA, SA and OA, at the in vitro conditions and tested concentrations, do not exert detrimental effects on bovine sperm function and morphology. These results provide insights that contribute to our understanding of how fatty acids can impact the reduction of fertility rates in cows facing NEB. This, in turn, lays the foundation for additional critical investigations in this area. Further studies are necessary to validate these findings in vivo.

Resynchronization of follicular wave using long-acting injectable progesterone or estradiol benzoate at 14 days post-timed AI in Bos taurus x Bos indicus beef heifers.

We compared pregnancy rates in beef heifers resynchronized 14 days after the first timed-artificial insemination (TAI) using a P4 intravaginal device associated with either long-acting injectable progesterone (iP4) or estradiol benzoate (EB). Braford and Brangus heifers were submitted to a TAI (D0). On D14, all animals were given a P4 intravaginal device and were randomly divided into two groups, EB (1 mg; n = 339); or iP4 (75 mg; n = 338). On D22, P4 devices were removed, and non-pregnant (NP) heifers were identified by assessing morphological luteolysis with Doppler ultrasonography. The NP heifers had the dominant follicle diameter measured and were submitted to a second TAI on D24. Dominant follicle diameter (mm) on D22 in NP heifers did not differ (P > 0.05) between EB (9.77 ± 0.25) and iP4 (9.92 ± 0.22) groups. No difference was observed between EB and iP4 groups for pregnancy rate on D22 (56.3% vs. 60.1%, respectively), and D40 post-first TAI (49.6% vs. 53.3%, respectively). The rate of potential pregnancy losses from D22 to D40 did not differ between EB (12%, 23/191) and iP4 (11.3%, 23/203) groups. The resynchronization pregnancy rate in the EB group (45.9%, 68/148) was greater (P<0.05) than the iP4 group (31.8%, 43/135). In conclusion, treatment with either 1 mg EB or 75 mg iP4 in combination with P4 device at 14 days after TAI are equally safe for the ongoing pregnancy. The EB treatment can improve the reproductive efficiency, as it resulted in greater resynchronization pregnancy rates than iP4 treatment in beef heifers resynchronized 14 days after TAI.