Influence of fasting and post-fast diet energy level on feed intake, feeding pattern and blood variables of lambs.

Trials were conducted to determine the influence of feed and water deprivation on feed intake, plasma glucose, free fatty acids (FFA), urea-N (PUN), serum insulin and growth hormone (GH) in lambs. In Trial 1, 12 Hampshire X Suffolk lambs (avg wt 30.5 kg) were deprived of feed and water for 0, 24, 48 or 72 h. During the first 8 d of realimentation, feed intake was depressed more (P less than .05) by longer periods of deprivation. In Trial 2, 12 crossbred lambs (avg wt 50 kg) were deprived of feed and water for 0 or 72 h. During the first 4 d of realimentation, feed intake was lower (P less than .05) in deprived than in fed lambs. The depressed feed intake could be detected within 30 min of feeding. In Trial 3, 12 crossbred lambs (avg wt 40 kg) were fasted for 0 or 72 h, and blood samples were obtained at -5, 30, 60, 120 and 180 min postprandial. On the 1st d of realimentation, lambs previously fasted had abnormal serum hormone patterns compared with nonfasted controls. On d 2 of realimentation, lambs previously fasted had higher (P less than .05) insulin, glucose and FFA than controls. On d 4 of realimentation, lambs previously fasted had higher insulin:GH ratios and lower PUN than controls. Results of these trials suggest that depriving lambs of feed and water for 72 h reduces subsequent feed intake for 4 d or more. Postprandial blood metabolite patterns are abnormal for a similar length of time.