Influence of feed withdrawal on intestinal characteristics of broilers
In the poultry industry, the removal of feed prior to processing is a necessary step for reducing the incidence of carcass contamination and the potential for foodborne illness caused by carcass contamination. Unfortunately, this procedure often increases intestinal colonization by pathogens, though the mechanisms are not well-characterized. Therefore, four experiments were conducted to characterize the changes that occur within the gastrointestinal tract (GIT) during feed withdrawal (FW) and with different dietary treatments. Broilers (39 to 62d of age) were subjected to FW periods of 0, 8, 10, 12, and/or 24h in each experiment, and GIT morphology, microbiology, and electrophysiology were measured. In experiment (Exp) 1, ileal villus width and crypt depth were decreased by FW while jejunal villus height increased, though ileal cell migration rate was not affected by FW. After 24h of FW, mucus quantity was reduced. For Exp. 2, microbial communities were less diverse, as indicated by the reduction in bacterial species and diversity during 24h FW. Dietary copper increased the similarity of bacterial communities while dietary antibiotics reduced similarities. In Exp. 3, electrophysiology measurements demonstrated that 24h FW caused reductions in initial current and transepithelial resistance, indicating a reduction in tissue viability and integrity. Intestinal permeability to 4,400 MW and 40,000 MW markers was reduced by 24h of FW. The final experiment examined how oxyhalogen and ionic salts (OIS) affected broiler performance and Salmonella growth in vitro. Dietary addition of OIS increased BW and led to greater phosphorus and nitrogen retention in young chicks, but the advantages did not last until 42d. Additionally, Salmonella growth was inhibited by 0.025% OIS. These experiments suggest that the increased pathogen colonization that occurs during FW may occur in part due to the reduced mucus quantity combined with a reduced intestinal integrity. Furthermore, dietary additions of copper sulfate and antibiotics had a significant effect on the bacterial communities, while OIS inhibited Salmonella growth, and these additives may be effective in changing GIT bacterial populations.