Importance of temperament in the pregnancy by timed insemination in bovine females Bos taurus indicus

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The aim of this research was to evaluate the effects of the temperament of bovine females Bos taurus indicus submitted to a timed artificial insemination (TAI) protocol on the concentrations of cortisol, diameter of the largest follicle, pregnancy by TAI on Days 30 (P/TAI 30) and 60 (P/TAI 60) after TAI. Nellore cows (n = 2702) of 45 ± 7 days post-partum were submitted to the same TAI protocol. On D -10 devices containing 1 g of progesterone were inserted into the vagina and 2 mg of estradiol benzoate were applied intramuscularly. On D -2, the devices were removed and 530 µg of sodium D-cloprostenol, 300 IU of equine chorionic gonadotropin, and 1 mg of Estradiol Cypionate were applied. Forty-eight hours after the final injection, the cows were submitted to TAI (D 0). The temperament of the cows was rated on a numerical scale from 3 to 12 using the composite reactivity score (RS) on D -10. The RS included the evaluation of the movement and breathing while the animal was in the cattle chute and the exit velocity. Cows were classified as Calm (RS ≤ 4; n = 830; Calm group), Reactive (RS = 5 to 8; n = 1313; Reactive group) and Very Reactive (RS ≥ 9; n = 559; Very Reactive group) and 5% of the cows of each group were submitted to blood collection for the subsequent plasmatic cortisol concentration measurement by ELISA. It was observed that Calm group had lower concentration of cortisol than did the Reactive and Very Reactive groups (35.07 ± 1.78, 50.58 ± 2.76, and 54.45 ± 3.39 nmol/L, respectively). The Calm group had diameter of the largest follicle on the day of TAI compared to Reactive and Very Reactive groups (14.4 ± 0.2, 13.6 ± 0.4, and 13.2 ± 0.2 mm, respectively). The Calm and Reactive groups had higher P/TAI compared to the Very Reactive Group on Day 30 (56.4%, 57.0%, 51.0%, respectively) and on Day 60 (50.0%, 47.3%, 42.7%, respectively). In conclusion, temperament influences the reproductive efficiency of bovine females Bos taurus indicus submitted to TAI protocols.