Relationship between thermal environment and morphophysiological, performance and carcass traits of Brahman bulls raised on tropical pasture: A canonical approach to a set of indicators.

The purpose of this study was to understand and discuss the relationships of the thermal environment, morphophysiological response, performance, and carcass traits of Brahman bulls from weaning at 18 months exposed to grazing conditions based on the physiological and evolutionary rationale behind the different proposals for the thermal adaptation of zebu cattle. Fifty-three uncastrated and clinically healthy bulls with birth and weaning weight of 34.0 ± 3.32 kg and 215.5 ± 44.75 kg, respectively, were evaluated. Fifteen canonical correlations were estimated, but only six were significant: thermal environment × thermoregulatory responses (r _c  = 0.4635; P = 0.0413); thermal environment × performance (r _c  = 0.4338; P = 0.0218); thermoregulatory responses × performance (r _c  = 0.5119; P = 0.0071); hair coat characteristics × performance (r _c  = 0.4939; P = 0.0273); hormone × carcass traits (r _c  = 0.5408; P = 0.0698); and performance × carcass traits (r _c  = 0.9644; P < 0.0001). Thermal environment, thermoregulatory responses and hair coat morphology influence of 18.81%, 21.49% and 24.40%, respectively, were found in the performance. We also concluded that (i) rectal temperature (R _T ) is a homoeothermic indicator; (ii) sweating rate (S _R ) is an important heat dissipation mechanism to explain the adaptation of zebu animals in the tropics and is related to weight at 550 days (W ₅₅₀ ); (iii) coat morphology, especially length (H _L ), diameter (H _D ) and hair density (N _D ) are related to animal performance; and (iv) hormonal profile, mainly T ₄ , influences the carcass traits (yield, weight, subcutaneous fat and marble meat).
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