Some Effects of Shade on Zebu Cross Cattle in a Feedlot

The comparative performance of shaded and unshaded Zebu cross steers was studied in a Queensland feedlot from January to May 1992. The provision of shade gave no significant (P > 0.05) advantage in liveweight gain (182 V. 177 kg), feed conversion ratio (9.4 v. 9.8 kg of fresh feed/kg liveweight gain), carcase weight, dressing percentage, P8 rump fat, eye muscle area, saleable meat yield, meat colour, fat colour, fat content, marbling or ultimate pH to the shaded group compared to the unshaded group. At no time did steers exhibit open-mouth breathing or aberrant behaviour. A significant (P c 0.05) relationship was found between rectal temperature and dry bulb temperature (r2 = 0.60) but not between rectal temperature and wet bulb temperature. Although the slopes were the same in the relationship of rectal temperature against dry bulb temperature for the treatments, the unshaded steers had significantly (P < 0.05) higher rectal temperature than shaded steers for any particular dry bulb temperature. The equations were; y = 37.95 + 0.036x and y = 38.09 + 0.036x for shaded and unshaded respectively, where y is rectal temperature and x dry bulb temperature in “C.