ARS | Publication request: Effects of dietary alfalfa inclusion on Salmonella Typhimurium populations in growing layer chicks

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 20, 2012
Publication Date: October 5, 2012
Citation: Escarcha, J.F., Callaway, T.R., Byrd II, J.A., Miller, D.N., Edrington, T.S., Anderson, R.C., Nisbet, D.J. 2012. Effects of dietary alfalfa inclusion on Salmonella Typhimurium populations in growing layer chicks. Foodborne Pathogens and Disease. 9:945-951.

Interpretive Summary: High-fiber containing feeds are fermented by the microbial population in the gut of chickens, which has been shown to reduce populations of the foodborne pathogenic bacteria Salmonella. However, the effect of the addition of high-fiber feedstuffs to the diet of growing chicks has never been demonstrated. This study utilized chicks artificially inoculated with Salmonella that were fed 0, 25, or 50% of their diet replaced with alfalfa meal for 7 days. Alfalfa feeding reduced cecal populations of Salmonella by approximately 10 fold and reduced the number of birds positive for Salmonella in the crop and cecum. Increasing alfalfa in the diet increased volatile fatty acid concentrations in the cecum, which may be responsible for the decrease in Salmonella populations. Alfalfa supplementation also increased the microbial diversity of the cecum. Collectively, results indicate that providing a fermentable substrate can affect fatty acid production and the microbial ecology of the gut, which in turn can reduce Salmonella colonization via natural competitive barriers.

Technical Abstract: Reducing Salmonella in poultry has been a paramount goal of the poultry industry in order to improve food safety. Inclusion of high-fiber fermentable feedstuffs in chicken diets has been shown to reduce the incidence of Salmonella colonization in laying hens, but no work has been performed in growing birds previously. Therefore, the present study was designed to quantify differences in artificially inoculated cecal Salmonella Typhimurium populations in growing layer chicks (n = 60 in each of 2 replications) fed 0, 25, and 50% of their diet (w/w) replaced with alfalfa meal from d7 to d14 after hatch. Alfalfa supplementation reduced cecal populations of Salmonella by 0.95 and 1.25 log10 CFU/g in the 25% and 50% alfalfa groups compared to controls and reduced (P < 0.05) the number of cecal- and crop-positive birds compared to controls. Increasing levels of alfalfa increased (P < 0.05) total VFA and the proportion of acetate in the cecum. Surprisingly, alfalfa inclusion did not negatively impact ADG in birds when fed over 7 d. Alfalfa inclusion at 50% of the diet increased (P < 0.05) the number of bacterial genera detected in the cecum compared to controls and also altered proportions of the microbial population by reducing Ruminococcus and increasing Clostridia populations. Results support the idea that providing a fermentable substrate can increase gastrointestinal VFA production and bacterial diversity, which in turn can reduce colonization by Salmonella via natural competitive barriers. However, further studies are obviously needed so that we can more fully understand the impact of changes made in diet or management procedures of poultry production.