Influence of prefast feed intake on recovery from feed and water deprivation by beef steers.

A trial was conducted with 60 steers (257 kg) to determine the influence of prefast feed intake on recovery from feed and water deprivation. For 3 d, steers were fed a 35% roughage diet at 1 (LI) or 1.75% (MI) of body weight or ad libitum (AL). Steers were then deprived of feed and water for 24 h, limit-fed and watered for 24 h, deprived of feed and water for 48 h and then allowed ad libitum feed and water consumption for 2 wk. A fourth group of control steers was fed at 1.75% of body weight during the alimentation period and was not fasted. Realimentation feed intake was positively related to prefast feed intake, with the order of realimentation feed intake being AL greater than MI greater than LI (P less than .05). During deprivation, rumen volume declined (P less than .05) in AL-fed steers, but was not affected in LI and MI steers. Blood hemoglobin and serum urea-N increased during deprivation in all fasted groups. Prefast serum cholesterol levels were inversely related to prefast energy intake. During deprivation, rumen fluid total volatile fatty acid (VFA) concentrations and propionate and butyrate molar proportions declined (P less than .05) and acetate, isobutyrate and valerate + isovalerate molar proportions increased (P less than .05). Results of this study indicate that an increased prefast feed intake will provide a greater reserve of energy, water and electrolytes to the steer during deprivation and result in a shorter postfast adaptation period.