Diet-related adaptation of the small intestine at weaning in pigs is functional rather than structural

Background: Incidence of diarrhea at weaning in commercial pigs is an important problem, and diet is thought to be a predisposing factor. The aim of this study was to determine the impact of switching from milk-based to cereal-based diets on the morphology and function of the small intestine of piglets using a model of delayed weaning to isolate the influence of the diet from that of environmental and social factors. Methods: Forty-five piglets received a milk-based diet for 5 weeks after weaning. Thirty piglets were then switched from milk-based to wheat- or barley-based diets. mimicking the dietary change that occurs at weaning. The last 15 piglets remained on the milk-based diet. Piglets were killed 4 days after the dietary switch, Jejunal mucosa morphometry and enzyme activities were measured. Ussing chambers were used to measure intestinal permeability to macromolecules, basal electrical properties, glucose absorption, and induced chloride-secretion. Results: Alkaline phosphatase- and sucrase-specific activities were higher in both groups of cereal-fed piglets than in milk-fed piglets. Dipeptidylpeptidase IV activity was higher in wheat-fed piglets than in the other groups. Na+-dependent glucose absorption was 1.7-fold higher in cereals-fed piglets than in milk-fed piglets. Serotonin-induced and vasoactive intestinal polypeptide-induced chloride secretion was doubled in cereals-fed piglets. Dietary transition did not influence the other parameters. Conclusions: These results indicate that switching from milk to cereals increased some mucosal enzyme activities, intestinal Na+-dependent glucose absorption, and response to secretagogues. This Supports the hypothesis that dietary factors could initiate diarrhea in the presence of other aggravating factors, such as pathogens or environmental stress.