Can animal temperament influence weight gain, semen quality and reproductive performance of bulls?

Abstract

The objective of this study was to evaluate the influence of animal temperament on productive and reproductive aspects of Nellore bulls, testing the hypothesis that naturally more reactive animals present higher levels of stress-related hormones, which may influence the capacity of service, semen quality, freezing and sperm fertility. Twenty-four Nellore bulls will be selected and submitted to behavioral analysis. The bulls will be monitored monthly for 4 months through the measurement of serum testosterone and cortisol, weight gain, scrotal thermography, ecotexture and testicular hemodynamics evaluation (Doppler ultrasonography). Semen samples will be collected monthly by electroejaculation to evaluate the raw semen quality and post cryopreservation. In addition, seminal samples will be collected and cryopreserved for the in vivo fertility test involving fixed-time artificial insemination. The breeding capacity of the animals will be evaluated individually through exposure of bulls to cyclic cows, recording the number of mating performed over the evaluation time. Seminal plasma samples from the selected animals will be recovered for protein profile evaluation by mass spectrometry. Based on the proposed methodology, we intend to determine if there are differences in the reproductive capacity of beef bulls according to the animal temperament, characteristic that can be exploited for bovine reproductive selection and management purposes. (AU)