Effects of crude protein and lactose levels in diets on growth performance, intestinal morphology, and expression of genes related to intestinal integrity and immune system in weaned piglets

To evaluate the effects of crude protein (CP) and lactose (LAC) for weaned piglets on performance, intestinal morphology, and expression of genes related to intestinal integrity and immune system, 144 piglets with initial weight 7.17 ± 0.97 kg were allotted in a randomized design, in a 2 × 3 factorial arrangement (20.0% and 24.0% CP and 8.0%, 12.0%, and 16.0% LAC) with eight replicates. Piglets fed 20.0% CP had greater weight gain and feed intake. Including 12.0% LAC in the 20.0% CP diet provided higher villous height in the duodenum than 8.0% LAC, and 12.0% or 16.0% LAC in the 24.0% CP diet resulted in higher villous height in the jejunum and ileum, and higher villi/crypt ratio in the ileum than 8.0% LAC. No effects of CP and LAC on interleukin-1β and tumor necrosis factor-α mRNA were observed. The 16.0% LAC diet provided higher gene expression of transforming-β1 growth factor. Feeding 20.0% CP resulted in better performance than 24.0% CP. The 12.0% LAC diet promoted greater genetic expression of occludin and zonula occludens. Including 12.0% LAC in the diet may improve intestinal epithelial morphology and integrity, and these improvements are more evident when piglets are fed diets with 24.0% CP.