Vitamin E reduces the reactive oxygen species production in dominant follicle during the negative energy balance in cattle.

In the postpartum period, there is an increase in non-esterified fatty acids (NEFA) in both serum and follicular fluid (FF) of cattle. The increase in fatty acid concentration results in increased production of reactive oxygen species (ROS) that can compromise bovine fertility. The objectives of this study were to characterize the lipid profile found in the FF of cows experiencing induced negative energy balance (NEB) and to evaluate the effect of α-tocopherol in the prevention of oxidative stress in the serum and FF of cows. Twenty-nine beef cows were divided into groups: (1) control; (2) Fasting for 24 days; and (3) Fasting + VitE. Between D0 and D4 blood samples were taken to assess concentrations of NEFA, ROS production, total antioxidant capacity (FRAP), lipid peroxidation, and α-tocopherol (vitamin E). On D4, follicular aspiration was performed for analysis of FF from the dominant follicle. Our results demonstrate that fasting was effective in causing increased fat mobilization in animals. The increase in serum concentration of C18:1c9 was reflected in the FF of fasting cows. Serum α-tocopherol concentration was higher in the control and Fasting + VitE groups compared to the Fasting group. In FF, there was an increase of α-tocopherol in the Fasting + VitE group in comparison to Fasting cows. There was an increase in ROS production in the serum of fasting cows. ROS production in FF was higher in the Fasting compared to the Fasting + VitE group. Vitamin E has beneficial effects in reducing ROS production in the dominant follicle of cows in NEB.

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.