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Influence of Pre-Fast Dietary Roughage Content on Recovery from Feed and Water Deprivation in Beef Steers¹

U.S. Department of Agriculture, Bushland, TX 79012 and Texas A&M University Center, Amarillo 79106

Abstract

Sixty steer calves of mixed British breeding averaging 268 kg were randomly assigned to four treatment groups of 15 calves each to determine the influence of pre-fast dietary roughage content on recovery from feed and water deprivation. Three groups were fed diets containing either 84 (HR), 60 (MR) or 35% (LR) roughage at 1.75% of body weight for 3 d. Calves in these three groups were deprived of feed and water for 24 h, limit-refed and watered for 24 h, and deprived of feed and water for 48 h (deprivation). Calves were then fed the MR diet ad libitum for 2 wk. The fourth group of control steers was continuously fed the MR diet throughout the experiment. Realimentation weight gains and feed intakes were not affected by pre-fast diet roughage content. Blood packed cell volume increased (P<.05) during deprivation. Blood potassium was not affected by deprivation but declined (P<.05) upon refeeding. Plasma urea-N increased (P<.05) during deprivation but returned to pre-fast concentrations by d 3 of realimentation. Ruminal volume was not significantly affected by deprivation but increased (P<.05) by 50 to 100% upon refeeding. Ruminal fluid total volatile fatty acid (VFA) concentrations declined (P<.05) during deprivation. On d 3 of realimentation, a linear contrast (P<.05) was observed between total VFA concentrations and the pre-fast diet roughage content. Ruminal fluid propionate and butyrate molar proportions tended to decline during deprivation but increased (P<.05) during the first 3 d of realimentation. Minor VFA molar proportions increased (P<.05) during deprivation and declined (P<.05) during realimentation. Results of this study indicate that when pre-fast feed intake is held constant, the pre-fast diet roughage content will not appreciably affect the recovery of normal ruminal activity and feed consumption in steers.

¹ Contribution from USDA, Agric. Res. Serv., in cooperation with the Texas Agric. Exp. Sta., Texas A&M Univ., College Station 77843.

² USDA-ARS, Conservation and Production Res. Lab., Bushland, TX 79012.

³ Texas A&M Univ. Res. and Ext. Center, Amarillo 79106.

⁴ Mention of a specific product or piece of equipment does not constitute an endorsement by the USDA or the Texas Agric. Exp. Sta., and does not imply their approval to the exclusion of other products that may be suitable.