Influence of realimentation diet on recovery of rumen activity and feed intake in beef steers.

Two trials were conducted to determine the influence of realimentation diet energy, protein, B-vitamin (BV) and Lactobacillus acidophilus (LAC) content on recovery of rumen activity and feed consumption in beef steers. In trial 1, ruminal-fistulated steers were fasted and refed 1) prairie hay, 2) 10% protein (LCP), 3) 12.5% protein (MCP), 4) LCP + BV or 5) LCP + LAC. In trial 2, calves were fasted and refed 1) 60% cottonseed hulls-40% alfalfa dehy (high roughage), 2) LCP, 3) 15% protein (HCP), 4) LCP + BV or 5) LCP + LAC. Rumen fermentative capacity declined 74% (P less than .05) during feed and water deprivation, but returned to control levels by d 7 of realimentation. On d 3 of realimentation, steers fed the LCP and MCP diets had molar proportions of ruminal butyrate in excess of 35%. Steers fed the hay, LAC and BV diets did not have a high butyrate fermentation. In trial 2, calves lost about 15% of their body weight during feed and water deprivation. Calves fed the high roughage diet appeared to return to prefast feed and energy intakes more slowly than steers fed the medium roughage diets. Results of this study indicate that rumen fermentative capacity is a factor limiting feed intake in fasted calves for 7 to 14 after the reintroduction of feed and water.