Effects of environmental stress on physiological parameters of feedlot sheep in the northeast of Brazil

A study was conducted to determine the effect of environmental stress on physiological criteria of feedlot sheep. Treatments consisted of two different housing conditions (shade and no shade) and two levels of concentrate in the diet: high concentrate (70% of concentrate and 30% of roughage-70C:30R) and low concentrate (30% of concentrate and 70% of roughage-30C:70R). Animals raised under shade and fed a high concentrate diet (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 30.6degreesC, under shade, and 32.1degreesC, under sun and the values of temperature humidity index (THI) were 82.3 and 81.1, respectively. Animals fed diet with higher concentrate level (70C:30R) also showed higher respiratory frequency (RF), either raised under shade (87 mov/min) or under the sun (7 1 mov/min.). Rectal temperature (RT) was higher in the afternoon (39.1degreesC) than in the morning (38.9degreesC), but animals raised under shade and fed 70% concentrate showed the highest RT value (39.3degreesC). Regardless of housing conditions, the animals fed 70% concentrate showed greater value of rectal temperature (39.2degreesC) than those fed 30% concentrate (38.8degreesC). Therefore, the type of diet affected the animal response to housing conditions. Once Santa Ines sheep showed lower performance when raised under no shade, they are inherently more sensitive to environmental stress.