Características de termorregulação de touros jovens da raça Nelore no inverno e no verão

Abstract

The objective of this study was to evaluate the effects of winter and summer seasons on the thermoregulation characteristics of young nelore bulls. Sixty - one Nellore bulls aged 7 to 9 months were used. The rectal (TR) and body surface temperature in the head, withers, groin and hock were measured. The ambient temperature (Ta) was also quantified. The thermal gradients between rectal temperature and mean surface body temperature (TR-TCS), mean surface body temperature and air temperature (TCS-Ta) and rectal temperature and air temperature (TR-Ta) were calculated. In winter, the mean values of TR and TCS were, respectively, 39.18ºC and 32.28ºC and in the summer were 39.16ºC and 32.59ºC, respectively. In summer, the TCS-Ta gradient (5.86) was superior to winter (3.66) and the TR-Ta gradient in summer (12,43) was superior to winter (10,55). The rectal temperature of young Nelore bulls raised in tropical environment is not influenced by the winter and summer season, since the TCS can modify according to the air temperature.