Influence of pre-fast dietary roughage content on recovery from feed and water deprivation in beef steers.

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 less than .05) during deprivation. Blood potassium was not affected by deprivation but declined (P less than .05) upon refeeding. Plasma urea-N increased (P less than .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 less than .05) by 50 to 100% upon refeeding. Ruminal fluid total volatile fatty acid (VFA) concentrations declined (P less than .05) during deprivation. On d 3 of realimentation, a linear contrast (P less than .05) was observed between total VFA concentrations and the pre-fast diet roughage content.(ABSTRACT TRUNCATED AT 250 WORDS)