Effect of management strategies on reducing heat stress of feedlot cattle: feed and water intake.

Abstract

Three experiments were conducted to evaluate management strategies designed to decrease heat stress of cattle finished during the summer. In Exp. 1, 144 Angus crossbred yearling steers were assigned to three treatments: 1) ad libitum access to feed at 0800 (ADLIB); 2) fed at 1600 with feed amount adjusted so that no feed was available at 0800 (BKMGT); and 3) fed at 1600 at 85% of predicted ad libitum levels (LIMFD). Treatments were imposed for 23 d of an 82-d study, after which all steers were fed ad libitum at 0800. Treatment did not affect (P > 0.10) overall DMI, although ADLIB cattle tended to consume less feed. Overall water intake was decreased (P < 0.05) by 6.8 L x animal(-1) x d(-1) for LIMFD vs. ADLIB steers. In Exp. 2, 96 Angus crossbred yearling steers were assigned to three treatments: 1) control, no water application; 2) water applied to the pen surfaces between 1000 and 1200 (AM); and 3) water applied to pen surfaces between 1400 and 1600 (PM). Water intake and DMI did not differ among treatments; however, feed efficiency of AM steers was superior (P = 0.06) to that of PM steers. Conversely, marbling scores of PM steers were higher (P = 0.06) than those of AM steers. In Exp. 3, 192 crossbred steers were used to determine the effects of feeding time (0800 [AMF] vs. 1400 [PMF]), with (WET) and without (DRY) sprinkling (20 min every 1.5 h between 1000 and 1750). Feed DMI did not differ among treatments; however, water intake and marbling scores were highest (P < 0.05) for AMF/DRY steers. During these experiments, bunk scores (0 = <10% of feed delivered remaining; 1 = 10 to 50% of feed remaining; 2 = >50% of feed remaining) were assigned to each pen at various times during the day. In Exp. 1, bunk scores of BKMGT pens remained similar (P > 0.20) under varying environmental conditions, whereas LIMFD steers had lower scores (P < 0.05) as days on feed increased, even under hot environmental conditions. In Exp. 3, bunk scores of PMF/WET steers tended to be lower (P < 0.10) at 1700 and 2000 compared with PMF/ DRY pens under mild heat stress but not under severe heat stress. Alternative feeding regimens and sprinkling can alter the feed intake pattern of steers. Heat stress management strategies imposed in these experiments had minimal effects on cattle performance. Such strategies would be most useful for decreasing the susceptibility of cattle to hyperthermia and reducing related feedlot cattle deaths without adversely affecting performance.