Effect of shade on respiration rate and rectal temperature of Angus heifers

Abstract

The effect of shade on respiration rate and rectal temperature of grain-fed Angus heifers was examined in a 21-day study. Six heifers were housed in individual outside yards (15 m²). Three of the yards had shade, and 3 did not. Each pen had an individual water bowl and feed bunk. Three data collection periods were used during which time the cattle were exposed to hot conditions (mean heat load index > 83). Overall the heifers with access to shade had lower rectal temperatures and respiration rates than those without access to shade. The largest difference was seen in the afternoon (1201-1700 h), with little or no differences seen at other times of the day. Dry matter intake was not affected by treatment, however, there were changes in eating dynamics, with un-shaded cattle eating more at night. Provision of shade resulted in lower rectal temperature and respiration rate during periods of peak heat load.