Resumo

QUINTERO-MORENO, Armando et al. Heat Tolerance in ½ Senepol - And ⁵/₈ Holstein -³/₈  Brahman Crossbred Calves.. Rev. Cient. (Maracaibo) [online]. 2007, vol.17, n.5, pp.464-472. ISSN 0798-2259.

Two trials were conducted to determine heat tolerance between crossbred ½ Senepol- (S-) and ⁵/₈ Holstein-³/₈ Brahman (HB). Differences between crossbred in trial 1, and crossbred and ambient temperature (Ta: 25 and 34°C) in trial 2 were evaluated through rectal temperature (Tre), respiration rate (RR), heat tolerance index (HTC), coefficient of adaptability (CA), average daily gain (ADG), and plasma cortisol. Trial 1 used 324 observations in 18 S- calves and 12 HB calves, while trial 2 used 90 observations in 8 S- calves and 7 HB calves. The statistical analysis of the parameters evaluated was carried out by mixed model with repeated measurements, whilemeans the ADG was perform by T-test. In trial 1, S- and HB calves had similar heat tolerance (P>0.05). In trial 2, Tre and RR in HB were greater (P<0.05) than S- calves, and also HTC, CA and ADG were the best in S-. At 34°C of Ta, the HB calves had significantly (P<0.05) greater Tre, and lower HTC than S- calves (P<0.01). The results demonstrate the great heat to- lerance of the crossbred Senepol.

Palavras-chave : Adaptation; heat tolerance; crossbred; tropics; calf.