Intestinal villus recovery in chickens refed semi-purified protein-, fat-, or fibre-free pellet diets

1. To determine which macronutrient, protein, fat, or fibre is most effective at inducing structural recovery of intestinal villi after feed withdrawal, male layer chickens were allotted to the following groups: intact control (IC), 3-d feed withdrawal (F), ad libitum refeeding of a formula mash diet (AFM), or force-feeding of a formula (FFP) or semi-purified well-balanced (FSP), protein-free (FSPP), fat-free (FSPF), or fibre-free (FSPFi) pellet diets for one day after 3-d feed withdrawal. 2. After refeeding, the formula diet groups increased in villus height and apparent area. However, not all of the semi-purified groups recovered to the levels of the formula diet groups in all light microscopic variables, except in terms of a further decrease in cell mitosis in the FSPP group compared to the F group. Of the semi-purified groups, the FSPFi group tended to be the highest for all variables. This result suggests that the semi-purified diets did not induce villus recovery faster than the formula diet, especially in the case of the protein-free pellet diet. 3. After refeeding, a smooth surface of villus tip in the F group changed to a rough surface, with cell protuberances in the AFM group. This morphological recovery was clearer in the FFP group. Compared with the FFP group, the semi-purified groups had cell protuberances which extended further into the intestinal lumen, and more cell clusters. Among the semi-purified groups, epithelial cells were smaller in the FSPP and larger in the FSPFi than in the other groups. This result suggests that the semi-purified diet can induce a quicker cell recovery than the formula diet but that the protein-free diet is the slowest. 4. The present study demonstrates that protein is the most important nutrient for the recovery of intestinal villi after feed withdrawal.