INFLUENCE OF A PROPIONATE LOAD IN FED OR UNFED LAMBS ON BLOOD METABOLITES AND HORMONE PATTERNS

Six crossbred wether lambs were used in a crossover design to determin e the effects of a 3-d feed and water deprivation period on metabolite and hormonal response to a propionate load. During each period of the crossover design all lambs were limit-fed (700 g/d) a 36% concentrate diet for 16 d, then three of the six lambs were deprived of feed and water for 3 d. All lambs were then limit-fed (700 g/d) the 36% concent rate diet (realimentation). Propionate loading tests were performed 4 h before feeding on d 1, 5, and 9 of the realimentation period. A 1.84 M propionate solution(3 mmol/kg BW) was infused into the right jugula r vein and blood samples were obtained from the left jugular vein at i ntervals for 4 h after infusion. At the end of the 3-d feed and water deprivation period, fed lambs had greater serum insulin(P < .02), acet ate (P < .01), and glucose (P < .05) concentrations and lower plasma-f ree fatty acids (P < .01) and urea N (P < .05) concentrations than unf ed lambs. On d 1 of realimentation, previously unfed lambs had greater postinfusion growth hormone (P < .05), free fatty acid (P < .01), pro pionate (P < .07), lactate (P < .04), and urea N (P < .05) concentrati ons and lower serum insulin (P < .02), and acetate (P < .03) concentra tions than fed lambs. Serum prolactin concentrations increased (P < .0 2) postinfusion in unfed lambs but not in fed lambs. Results of this s tudy are interpreted to indicate that appreciable metabolic adaptation s occur during feed and water deprivation but that these metabolic cha nges are corrected within 5 d of realimentation.