A study was conductedto determine the effect of environmental stress on physiological criteria offeedlot sheep. Treatments consisted of two different housing conditions (shadeand no shade) and two levels of concentrate in the diet: high concentrate (70%of concentrate and 30% of roughage-70C:30R); low concentrate (30% of concentrateand 70% of roughage-30C:70R). Animals raised under shade and fed a high concentratediet (70C:30R) had greater dry mater intake (1258 g/animal/day) and crude protein(0.8% of body weight (BW) and 18 g/BW0.75), as well as weight gain(247 g/animal/day). Air temperature in the afternoon was 30.6oC,under shade, and 32.1oC, under sun and values of temperature humidityindex(THI), 82.3 and 81.1, respectively. Animals fed more concentrate (70C:30R)had also higher respiratory frequency (RF), either raised under shade (87 mov/min)or under the sun (71 mov/min.). Rectal temperature (RT) was higher in the afternoon(39.1oC) than in the morning (38.9oC), but animals raisedunder shade and fed diets with 70% concentrate (70C:30R) had the highest valueof RT (39.3oC). Regardless of type of housing conditions, the animalsthat received more concentrate (70C:30R) had greater rectal temperature (39.2oC)than those fed a diet with less concentrate (30C:70R) (38.8oC). Therefore,the type of diet influenced the response of the animals to housing conditions.Moreover, Santa Inês sheep are susceptible to environmental stress becausehad lower performance when raised under no shade.
