The effect of previous body condition on appetite and associated insulin profiles in sheep

Abstract

AbstractThe 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 condition 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 grass pellet diet was 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 experiment (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. 0·071) 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 treatment (mean condition scores 3·15 (L) and 3·27 (H) (s.e.d. 0·091)) when fed both ad libitum and at a fixed level of 1200 g/day for consecutive 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 period of ad libitum feeding. There was no effect of feeding level (ad libitum v. 1200 g/day) on mean plasma insulin concentrations, but the mean basal plasma insulin concentration was higher in the H than in the L ewes (43·0 v. 29·0 mil per 1; P < 0·05). Fifteen minutes after the ingestion of a single 400 g meal, the plasma insulin concentration in the H ewes was higher than the mean prefeeding value (63·3 v. 41·7 mil per I; P<0·05) but there was no corresponding increase in the L ewes. The plasma insulin concentration 15 min after the intravenous administration of a single dose of 0·25 U per kg live weight of insulin ivas higher in the H than in the L ewes (1723 v. 1031 mil per 1; P < 0·01) but there were no differences between treatments in plasma glucose concentrations following insulin administration.It was concluded that previous body condition can affect contemporary VFI and this effect may be mediated by plasma insulin concentrations providing a long-term feedback signal to the brain. Keywords: body condition, food intake, insulin, sheep.