SUMMARY
ABSTRACT. Medeiros L.F.D., Rodrigues V.C., Vieira D.H., Souza S.L.G. de, Neto O.C., Oliveira C.A., Silva L. de A. da S., Figueiredo N. de & Azevedo S. F. de. [Determination of the physiologic parameters, thermal gradient and index of heat tolerance in different breeds of goats.] Determinação dos parâ- metros fisiológicos, gradiente térmico e índice de tolerância ao calor em diferentes raças de caprinos. Revista Brasileira de Medicina Veterinária, 37(4):275-285, 2015. Departamento de Reprodução e Avaliação Animal, Instituto de Zootecnia, Universidade Federal Rural do Rio de Janeiro, BR 465 Km 7, Seropédica, RJ 23851-970, Brasil. E-mail: diasmedeiros@yahoo.com.br The aim of this study was to evaluate the adaptation of different exotic breeds of goats through the physiologic responses of rectal temperature (RT), superficial temperature (ST), respiratory frequency (RF), cardiac frequency (CF), and the gradient between RT and ST, and the ST and air temperature (AT) and the heat tolerance index (HTI) by Baccari Junior, under the conditions of hot and humid climate of the Baixada Fluminense, South East Region of Brazil. Forty eight goats were used, being twelve animals of each breed: Saanen, Alpine (european origin), Anglo-nubian and Boer (african origin), between 24 and 30 months of age with medium weight of 50 kg, maintained in intensive system. There were significant difference in the RT, ST, RF and CF between breeds, by morning (P<0.05) and afternoon (P<0.01). The RT, ST, RF and CF of the animals range significant (P<0.01) between the shifts (morning and afternoon) and days, with significant interaction (P<0.01) between morning and afternoon and days, by consequence of the variation of AT. It was found the RT, ST, RF and CF of Saanen and Alpine goats were more higher (P<0.05) by morning (P<0.01) and by afternoon in comparison with Anglo-nubian and Boer goats. There was significant effect (P<0.05) between shifts (morning and afternoon) and breed for the termic gradient (RT-ST). The african breeds average showed more higher in both shifts in comparison as the european breeds. There were significant difference (P<0.05) between breeds for termal gradient (ST-AT). By the application of HTI, the Anglo-nubian and Boer breeds showed the HT higher (9.63 and 9.65) than the Saanen and Alpine breeds (8.89 and 8.91), respectively. The breeds of african origin (Anglo-nubian and Boer) showed more heat tolerance than the breeds of european origin (Saanen and Alpine) by HT. The breeds of european origin reveal more sensitive to termal stress. The african breeds showed more capacity for maintained the homeotermy. So, the use of Anglo-nubian and Boer breeds to increase the goats productivity under the conditions of hot and humid climate of the Baixada Fluminense, Rio de Janeiro State, can be advised.