The microbiota plays an important role in numerous physiological processes, pathogenesis, development, and metabolism in different animal species. In humans, several studies have demonstrated an association between the vaginal microbiota and fertility rates, and even success in assisted reproduction techniques. In the context of cattle reproduction, although few studies have addressed the microbiota in a healthy state (which is not associated with diseases that affect the reproductive tract of cows), changes in its composition also seem to influence fertility. This review aims to explain the importance of the reproductive microbiota in female bovines and what is available in the literature regarding its possible role in increasing fertility. What are the challenges involved in this process? Future perspectives on its use and manipulation as a selection or intervention tool. Will it be possible to one day extrapolate the findings to reality and apply them in the field? In short, understanding the role of the reproductive microbiota of female bovines can signal the prospect of increasing production, whether of milk or meat, from the same number of animals, as it can optimize reproductive efficiency and perhaps become an allied tool for the economic profitability and sustainability of livestock farming.

Oxidative stress (OS) induced by an imbalance in reactive oxygen species (ROS) levels in vitro impairs embryonic development. Here, we assessed the effects of alpha-lipoic acid (ALA) in in vitro production media on OS reduction, embryonic development, and cryotolerance of bovine embryos. We evaluated the effects of adding different concentrations of ALA (2.5, 5, 10, and 25 μM) to in vitro maturation (IVM) or in vitro culture (IVC) medium on embryonic development. We also determined the effects of adding ALA (25 μM) to the IVM and IVC medium in the same routine on the development and quality of embryos, ROS levels, and cryotolerance. Embryos were produced in vitro using conventional protocols for each treatment. The inclusion of ALA in the IVM and IVC media did not affect the development or quality of embryos; however, it reduced ROS levels in grade II embryos and increased hatching after 12 h on day 7 in grade I embryos and on day 8 in grade II embryos after warming. These findings prompt questions regarding the potential of ALA in improving embryo metabolism, considering the initial embryo recovery in the first few hours of embryo warming.

The application of Fixed Time Artificial Insemination (FTAI) protocols has strongly boosted artificial insemination in Brazilian bovine herds. The control of the estrous cycle with protocols based on progesterone and estrogen involves synchronizing the emergence of a follicular wave, controlling the progesterone phase, and inducing ovulation in a synchronized manner. The increase in pregnancy rates starts with the preparation of the breeding season and the choice of protocols and females. Thereafter, based on the characteristics of the property and the lots of animals, small adjustments can be made to the hormonal protocols as needed. Finally, resynchronization can increase usability by allowing multiple inseminations within short periods. The search for new strategies is of paramount importance for the development of the FTAI protocol and the increase in final pregnancy rates. Thus, this review sought to highlight the main critical points and adjustments of the FTAI protocols and their applicability in the reproduction of beef cattle.

This study evaluated the hemodynamic profile of the supratesticular artery and its relationship with pubertal status in young bulls to identify markers of early sexual maturation. Brangus bulls were evaluated at 15, 17, and 19 months of age. A breeding soundness exam was conducted, and supratesticular artery hemodynamics were evaluated using Doppler ultrasonography to determine arterial blood mean velocity (MV), pulsatility index (PI), and resistive index (RI). At the end of the study, bulls were retrospectively classified into two groups based on their pubertal status at 15 months of age: early-maturing (n = 13; pubertal at 15 months) or late-maturing (n = 15; non-pubertal at 15 months). Puberty was defined as the presence of an ejaculate with ≥10% motility and ≥ 50 × 10⁶ total sperm. Data were analyzed using a generalized linear mixed model for repeated measures, including group, time, and their interaction as fixed effects, with bull as a random effect. Body weight and scrotal circumference increased (P < 0.0001) with age, but there were no differences between groups. Early-maturing bulls had greater (P < 0.05) MV and lower (P < 0.05) PI and RI than late-maturing bulls at 15 months of age. These hemodynamic parameters converged by 17 months of age and remained similar between groups until the end of the study. Sperm concentration increased (P < 0.0001) with age in both groups and was greater (P < 0.0001) in early-maturing bulls than in late-maturing bulls throughout the study. Sperm motility and the percentage of morphologically normal sperm remained mostly unchanged in early-maturing bulls but increased (P < 0.05) throughout the experimental period in late-maturing bulls. In the late-maturing group, 33% of bulls reached puberty at 17 months and 73% reached puberty at 19 months of age. In conclusion, early-maturing bulls exhibit greater testicular blood perfusion at 15 months of age, which reflects early spermatogenesis and precedes the stabilization of sperm production and semen parameters during the peripubertal period. These results also indicate that supratesticular artery hemodynamics could indicate sexual precocity, and Doppler ultrasonography could be used as a tool for selecting animals with greater reproductive potential.