THE EFFECT OF PREVIOUS BODY CONDITION ON APPETITE AND ASSOCIATED INSULIN PROFILES IN SHEEP

The effect of previous level of body condition on appetite was studied in 47 housed Scottish Blackface ewes, which had been either thin (L: mean condition score 2.15, s.e. 0.030; no. = 24) or fat (H: mean condi tion score 3.15, s.e. 0.056; no. = 23) 8 weeks before the start of the experiment. The mean daily voluntary food intake (VFI) of a dried gra ss pellet diet suns higher for the L than for the H ewes (2176 v. 1727 g dry matter per day P < 0.001) during the first 6 weeks of the exper iment (period 1). Over this time, live weights increased from 60.5 or 69.9 (s.e.d. 1.68) to 68.4 or 75.6 (s.e.d. 1.94) and condition scores increased from 2.84 or 3.16 (s.e.d. 0.057) to 3.13 or 3.38 (s.e.d. 0.0 71) for the L and H ewes respectively. At the end of the 6-week period , plasma insulin concentrations were measured in 10 ewes from each tre atment (mean condition scores 3.15 (L) and 3.27 (H) (s.e.d. 0.091)) wh en fed both ad libitum and at a fixed level of 1200 g/day for consecut ive 11-day periods (period 2). Mean VFI was higher for the L than for the H ewes (2191 v. 1661 g dry matter per day; P < 0.05) over the peri od of ad libitum feeding. There was no effect of feeding level (ad lib itum v. 1200 g/day) on mean plasma insulin concentrations, but the mea n basal plasma insulin concentration was higher in the H than in the L ewes (43.0 v. 29.0 mU per 1; P < 0.05). Fifteen minutes after the ing estion of a single 400 g meal, the plasma insulin concentration in the H ewes was higher than the mean prefeeding value (633 v. 41.7 mU per 1; P < 0.05) but there was no corresponding increase in the L ewes. Th e plasma insulin concentration 15 min after the Intravenous administra tion of a single dose of 0.25 U per kg live weight of insulin was high er in the H than in the L ewes (1723 v. 1031 mU per 1; P < 0.01) but t here were no differences between treatments in plasma glucose concentr ations following insulin administration. It was concluded that previou s body condition can affect contemporary VFI and this effect may be me diated by plasma insulin concentrations providing a long-term feedback signal to the brain.