Influence on Beef Steers of Two Sequential Short Periods of Feed and Water Deprivation

Three trials were conducted to determine the influence of two sequential periods of feed and water deprivation on the rumen function, blood variables and feed intake of beef steers. In trial 1, two rumen-fistulated steers were fed a diet of grass hay, and, in trial 2, four rumen-fistulated steers were fed a 40% concentrate, pelleted diet. Steers were adapted to the diets for 3 weeks, then deprived of feed and water for 24 hr, fed and watered for 24 hr, deprived for 48 hr and again refed and watered. In trial 3, 24 feeder steers were fed either cubed alfalfa hay or a 40% concentrate diet and were deprived and refed and watered as in trials 1 and 2. In trials 1 and 2, in vitro rumen fermentative activity (RFA) and fermentative capacity (RFC) were significantly reduced by deprivation. After 5 days of refeed-ing, RFA and RFC were still significantly below prefast levels. During periods of deprivation, the ruminal molar proportions of acetate increased, while molar proportions of propionate and butyrate tended to decline. Rumen pH increased significantly during deprivation. Upon refeeding, rumen pH returned to prefast levels within 24 hr, whereas 3 to 5 days were required for rumen VFA to return to prefast levels. In trial 2, serum osmolality, glucose and urea N increased significantly during deprivation but declined to prefast levels within 24 hr after refeeding. In trial 3, calves fed alfalfa lost a greater percentage of their body weight during deprivation but regained their weight more rapidly than did calves fed the concentrate diet. Calves fed alfalfa returned to predeprivation levels of feed and water intake more rapidly than calves fed the concentrate diet.