Thermoregulatory responses of sindhi and guzerat heifers under shade in a tropical environment

• Autor(a) principal: Fonsêca, Vinícius de França Carvalho
• Data de Publicação: 2016
• Outros Autores: Cândido, Ebson Pereira, Gonzaga Neto, Severino, Saraiva, Edilson Paes, Furtado, Dermeval Araújo, Gama, Jean Francisco Pereira, Nascimento, George Vieira do, Saraiva, Carla Aparecida Soares, Almeida, Gabriel Henrique Oliveira
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Semina. Ciências Agrárias (Online)
• Texto Completo: https://ojs.uel.br/revistas/uel/index.php/semagrarias/article/view/25347
• topic: Heat tolerance; Physiological parameters; Prediction models; Zebu cattle.; Bovinos zebuínos; Modelos de predição; Parâmetros fisiológicos; Tolerância ao calor.

This study characterized the thermal environment and assessed the physiological aspects of acclimatization of Sindhi and Guzerat heifers in a tropical environment (Brazil) under shade. Eight Sindhi and eight Guzerat purebred heifers (Bos indicus) had their physiological traits measured twice a day (9:00 a.m. and 2:00 p.m.). Environmental data during the experimental period were collected at two-hour intervals between 5:00 a.m. and 5:00 p.m. The temperature-humidity (THI) and the black globe temperature-humidity (BGHI) indices were calculated, and surface temperature (St), respiratory rate (Rr), and rectal temperature (Rt) were collected, being used to estimate heat loss by cutaneous (Ec) and respiratory (Er) evaporation. In the warmer parts of the day (1:00 and 3:00 p.m.), the THI and BGHI reached values of 80.26 and 81.25, respectively. There was no significant difference in rectal temperatures between the breeds, but higher values were observed in the afternoon. Heat transfer by cutaneous evaporation reached 118.71±12.91 W.m-2 and 103.43±6.82 W.m-2 at 2:00 p.m. for the Sindhi and Guzerat heifers, respectively. Under these conditions (air temperature was between 29 and 30°C), 84% of the total latent heat loss in Sindhi and Guzerat heifers was represented by Ec. It can be concluded that Sindhi and Guzerat heifers can maintain homeothermy with minimal thermoregulatory effort under shade conditions in a tropical environment.