LAUSR

Abstract The present study was carried out to evaluate the effects of crude protein (CP) and lactose (LAC) levels on performance, intestinal morphology and gene expression associated to epithelial integrity and activation of the immune system of piglets fed antimicrobial free diets. A total of 120 weaned piglets with initial weight 7.88 ± 0.9 kg were assigned to a randomized block design, in a 2 × 3 factorial arrangement (20.0 and 24.0% CP and 8.0%, 12.0%, and 16.0% LAC), with 10 replicates. The reduction of dietary protein from 24.0 to 20.0% was based on concept of ideal protein, keeping the same SID lysine values. Piglets fed 24.0% CP had higher average daily feed intake (ADFI). Diets containing 12.0 or 16.0% LAC resulted in higher ADFI and average daily gain of piglets compared to 8.0% LAC. Pigs fed 12.0% LAC diets had greater final body weight than those fed 8.0 and 16.0% LAC diets. Piglets consuming 20.0% CP diets had lower SUN. Piglets fed 12.0 or 16.0% LAC diets had higher duodenum and ileum villous height (VH). Interactions were observed for duodenum, jejunum and ileum crypt depth (CD) and duodenum and ileum VH:CD ratio. Piglets fed 24.0% CP diet with 12.0 or 16.0% LAC had lower duodenum and ileum CD, and higher duodenum and ileum VH:CD ratio than those fed 8.0% LAC. At 24.0% CP, piglets fed 16.0% LAC had lower expression of Hp and ZO-1. Concentration of 12.0% LAC in the diet improves performance of piglets from 21 to 35 days of age regardless CP content. The inclusion of 12.0 or 16.0% LAC in the diet promotes improvements in intestinal morphology, which are more evident in the diet with 24.0% CP. In addition, increasing LAC content in the diet with 24.0% CP decreases the activation of the immune system and reduces the permeability of the intestinal epithelium.