Effects of an oat-based high-fibre diet an insulin, glucose, cortisol and free fatty acid concentrations in gilts

To understand the mechanism underlying the effect of high-fibre diets on fe eding motivation and stereotypic behaviour in pigs, non-pregnant gilts were given either concentrate or a high-fibre diet based on oat hulls and blood samples were assayed for cortisol glucose, insulin and free fatty acids. T he duration of eating was much longer for gilts on the high-fibre diet than gilts given concentrates. Concentrations of cortisol increased with food d elivery and this was most pronounced with the concentrate diet. Concentrati ons of free fatty acids decreased before feeding and those of glucose and i nsulin decreased temporarily immediately after feeding began. The diet had no marked effect on these changes, although the decrease for insulin was le ss evident for the concentrate diet. As feeding continued, free fatty acid concentrations decreased, while concentrations of insulin and glucose incre ased. The increase in glucose and insulin was fastest with the concentrate diet, although past-feeding peak values did not differ. Post-prandial corti sol and free fatty acid concentrations did not differ between diets. There was no evidence of a pre-prandial cephalic phase insulin or glucose respons e to feeding in the gilts although concentrations of both hormones decrease d immediately offer the gilts began to eat. The high-fibre diet tended to d elay the peak glucose and insulin response to meals, suggesting that the re duced feeding motivation following consumption of high-fibre diets does not involve the same mechanism as the increased satiety following increased en ergy intake. As well as reducing the occurrence of stereotypies, high-fibre diets decrease cortisol concentrations at feeding.