Effect of dietary supplementation of prebiotics and probiotics on intestinal microarchitecture in broilers reared under cyclic heat stress

This study was designed to evaluate the effect of dietary supplementation of prebiotics, mannanoligosaccharides (MOS) and/or probiotics (LBP) on intraepithelial lymphocytes (IEL) count, goblet cells (GC) count and differentiation and intestinal micro-architecture in broilers reared under cyclic heat stress. Day-old broilers (n=250) were randomly divided into five groups. Fifty birds were reared within the thermoneutral zone (TNZ). Remaining birds were subjected to cyclic heat stress from day 21 to 42 (35 degrees C, 75% RH, 8h/d). The birds were fed corn-soy-based basal diet or the same diet supplemented with 0.5% MOS (HS-MOS), or 0.1% LBP (HS-LBP), or their combination (HS-SYN). The birds were slaughtered on day 42. Tissue samples were collected from mid-duodenum, jejunum and ileum, and stained with haematoxylin and eosin or combined Alcian blue and PAS technique. All differences were considered significant at p<0.05. The IEL count increased in all intestinal segments of the HS group compared with the TNZ group and decreased in all supplemented groups compared with the HS group. Compared with the TNZ, heat stress reduced villus height, crypt depth and surface area in duodenum and ileum, and increased crypt depth in ileum. Villus width decreased in duodenum and jejunum compared with the TNZ group. Supplementation of LBP, MOS and SYN reversed all these changes in duodenum, while only increased villus height and surface area in ileum. In jejunum, the villus height and surface area increased with HS-LBP, and crypt depth increased with HS-MOS. The number of GC containing acid mucins (duodenum and ileum) and mixed mucins (ileum) were increased in the HS compared with the TNZ. Supplementation of MOS, LBP and SYN maintained the enhanced activity of goblet cells. In conclusion, dietary supplementation of MOS and/or LBP may be helpful in alleviating some of the detrimental effects of heat stress on microstructure of the broiler gut.