ARS | Publication request: Molting in Salmonella enteritidis-challenged laying hens fed alfalfa crumbles. I. Salmonella enteritidis colonization and virulence gene hilA response

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2007
Publication Date: June 15, 2007
Citation: Dunkley, K.D., McReynolds, J.L., Hume, M.E., Dunkley, C.S., Callaway, T.R., Kubena, L.F., Nisbet, D.J., Ricke, S.C. 2007. Molting in Salmonella enteritidis-challenged laying hens fed alfalfa crumbles. I. Salmonella enteritidis colonization and virulence gene hilA response. Poultry Science. 86:2101-2109.

Interpretive Summary: Understanding the ecological shifts of the microbial populations within the gastrointestinal tract during molt is important in understanding Salmonella colonization. Understanding these interactions will help future scientists reduce this foodborne bacteria. In this study, we looked at an alfalfa diet to determine its fermentation properties as well as the microbial ecology shifts in laying hens during a molt. The results of this study suggest that alfalfa molted hens retain microflora and fermentation activities which more closely correspond to full fed birds, and therefore could serve as a potential barrier to Salmonella colonization in the ceca of hens. These findings will help the egg industry understand the benefits of feeding a supplemental diet during a molt.

Technical Abstract: The objective of this study was to examine microbial population shifts and short chain fatty acids (SCFA) responses in the gastrointestinal (GI) tract of Salmonella Enteritidis (SE)-challenged molted and non-molted hens fed different dietary regimens. Fifteen Salmonella-free single comb Leghorn hens (>50 wks old) were assigned to three treatment groups of 5 birds each based on diet in two trials: 100% alfalfa crumbles (ALC); full-fed (FF), (non-molted) 100% commercial layer ration; and full feed withdrawal (FW). A forced molt was induced by a 12-day alfalfa diet and the feed withdrawal regimen. In all treatment groups each hen was challenged by crop gavage orally 4 days after molt induction with a 1-mL inoculum containing 10**6 cfu of Salmonella Enteritidis (phage type 13A). Fecal and cecal samples (days 4, 6, 8, 11 and necropsy on 12) were collected post challenged and microbial population shifts were evaluated by PCR-based 16S rRNA gene amplification and Denaturing Gradient Gel Electrophoresis (DGGE). In addition SCFA were evaluated for each treatment group. The concentrations of total SCFA in fecal and cecal contents for FW molted hens (1.88-56.40 umoles/mL) were significantly lower (P < 0.05) when compared to ALC (23.58-97.38 umoles/mL) and FF (27.0-157.80 umoles/mL) treatment groups. The overall trend of SCFA in cecal and fecal samples exhibited similar patterns. Dendrograms of amplicon band patterns yielded 67 and 68% similarity for comparison of fecal and cecal samples in Trials 1 and 2, respectively. In Trial 1 and 2 hens molted with ALC diet yielded similar amplicon band patterns of the FF treatment group in both fecal and cecal samples. In addition, FF and ALC treatment groups exhibited a higher percentage similarity coefficient (>90%) in Trial 2 than in Trial 1. The results of these studies suggest that alfalfa molted hens retain microflora and fermentation activities which more closely correspond to fully fed hens, and therefore could serve as a potential barrier to Salmonella colonization in the ceca of hens.