Join dynamics of voluntary feed intake, glycaemia and insulinaemia in ad libitum fed pigs

Short term regulation of voluntary feed intake depends on energy status of the animal. The latter can be assessed by plasma metabolite concentrations but lipogenesis and nutrient oxidation can also modify the respiratory quotient. This study aims to link the within-day dynamics of voluntary feed intake and those of blood metabolites in pigs fed ad libitum. Thirty-six pigs (mean BW 35 kg) were fed 6 diets with 2 levels of dietary fibre (13 or 18% NDF for LF and HF by addition of wheat bran, soybean hulls and sugar beet pulp) and 3 levels of aleurone (0, 0.2, or 0.4% for A0, A2 or A4, respectively). After a 2-week adaptation period, they were individually housed during 1 week in respiration chamber to measure feeding behaviour and gas exchanges. On the last day, the dynamics of blood metabolites was followed between 2 voluntary meals. Total feed intake was not modified by HF diet (1,452 g DM) but decreased with aleurone supplementation (-270 g/d for A4 vs A0; P<0.01). Daily heat production (1.37 MJ/kg BW0.60/day) and respiratory quotient (1.13) were not modified by diets. The HF diet resulted in less but heavier meals compared with LF diet (8.2 meals per d of 178 g DM vs 9.4 meals of 150 g, P<0.01). Aleurone supplementation decreased daily number of meals (-1.5 for A4 vs A0, P<0.01). Pre-meal plasmatic glucose concentration tended to decrease with HF diet (-7%) and pre-meal insulin concentration tended to increase with aleurone (3.8 vs 6.9 μU/ ml for A0 vs A2). During the first hour after the meal, glucose concentration was lower with HF compared with LF (P<0.01). Inter-individual variability of glucose profiles was important and glycaemia peaks ranged from 100 to 150% of the pre-meal level. Insulin and glucose profiles agreed and insulin profiles linked with the size of the first meal (P<0.01). To conclude, dynamics of voluntary feed intake cannot be explained only by profiles of glucose and insulin in ad libitum fed pigs.