Molting in Salmonella Enteritidis-Challenged Laying Hens Fed Alfalfa Crumbles. I. Salmonella Enteritidis Colonization and Virulence Gene hilA Response

Abstract

The objectives of this study were to enumerate Salmonella enterica serovar Enteritidis colonization in fecal, cecal, and internal organs, and to compare the level of virulence gene expression (hilA) of experimentally challenged laying hens fed different dietary molt-induction regimens. Twelve Salmonella-free Single Comb Leghorn hens (>50 wk old) hens were randomly assigned to each of 6 treatment groups designated based on diet in 2 trials: 1) feed withdrawal Salmonella Enteritidis-positive (FW+), 2) fully fed Salmonella Enteritidis-positive (FF+), 3) 100% alfalfa crumble Salmonella Enteritidis-positive (ALC+), 4) feed withdrawal Salmonella Enteritidis-negative, 5) fully fed Salmonella Enteritidis-negative, and 6) 100% alfalfa crumble Salmonella Enteritidis-negative. A forced molt was induced by a 12-d alfalfa diet and a feed-withdrawal regimen. On d 4 of the molt, all hens in groups 1, 2, and 3 were challenged by crop gavage with 1 mL of inocula containing approximately 10(6) cfu of nalidixic acid- and novobiocin-resistant Salmonella Enteritidis (phage type 13A). At the conclusion of both trials, all hens were euthanized and Salmonella Enteritidis colonization was enumerated in the cecal contents, liver, spleen, and ovaries. In addition, fecal (d 4 and 8) and cecal samples (necropsy at d 12) were collected postchallenge from treatment groups 1, 2, and 3 (Salmonella Enteritidis-positive) to quantify hilA expression by PCR. In both trials, all nonchallenged birds were Salmonella Enteritidis-negative; therefore, no further analysis was done. In trial 1, a 2-fold reduction in Salmonella Enteritidis colonization was observed in the ALC+ hens (log10 Salmonella Enteritidis of 1.99) compared with the FW+ hens (log(10) Salmonella Enteritidis of 3.89). In trial 2, a 4-fold reduction in Salmonella Enteritidis colonization was observed in the ALC+ hens (log(10) Salmonella Enteritidis of 1.27) compared with the FW+ hens (log(10) Salmonella Enteritidis of 5.12). In trial 2, Salmonella Enteritidis colonization in spleens was higher (P <or= 0.05) in FW+ hens compared with ALC+ and FF+ hens. Relative expression of hilA was higher (P <or= 0.05) in FW+ compared with FF+ hens, whereas the FF+ and ALC+ groups were not different (P > 0.05). In trial 2, hilA expression in FW+ hens was higher (P <or= 0.05) for d 6, 11, and 12, respectively, when compared with ALC+ and FF+ hens. The results of these studies support the concept that changes in the gastrointestinal tract microenvironment, such as those created during feed deprivation, encourage Salmonella Enteritidis virulence and susceptibility in molted hens.

Salmonella Pathogenicity and Host Adaptation in Chicken-Associated Serovars

“…Increased expression levels of the S. Enteritidis lacZY-hilA fusion gene in cells incubated in crop contents from birds that had undergone feed removal demonstrated that enhanced systemic invasiveness could be linked with increased expression levels of hilA (391). These findings were later replicated and confirmed in vivo by quantitative PCR (392). This increase in S. Enteritidis colonization and invasiveness also coincided with diminished numbers of lactic acid bacteria in the crop and reduced organic acids in the crop (391) and cecum (270,393) and led to major shifts in fecal and cecal bacteria compared to fully fed birds (270,394,395).…”

“…Several molt diets with fermentable substrate combinations have been screened in vitro and shown to support optimal avian cecal fermentation (396)(397)(398) and retain similar cecal microbial molecular profiles (397). In vivo application of some of these diets was shown to retain fermentation and GIT populations during molt while limiting the ability of S. Enteritidis to colonize the GIT and become invasive (255,270,392,399,400). The overall results of the studies demonstrate that there is a complex and important relationship between the microflora of the avian GIT and Salmonella, which is key to limiting the pathogen.…”

Effects of different force moulting methods on performance, egg quality and plasma metabolites in Japanese quails

“…Calcium concentration at the end of moulting was lower in forced-moulted birds than in controls. Dunkley et al (2007) reported similar reductions of calcium in forcedmoulted birds compared with control. Thus, it has been reported that maximising bone mineral deposition before onset of egg production and after moulting is vital to avoid bone weakness problems and improve eggshell qualities in older laying birds (Park et al, 2004).…”

“…Also, Donalson et al (2005) reported that using alfalfa in moulting diet resulted in higher Haugh units and lower shell breakage compared with control. Some studies have indicated that moulting affected blood parameters such as glucose, calcium and some hormones (Webster, 2003;Dunkley et al, 2007). The purpose of this study was therefore to investigate the effects of various forced-moulting methods on egg physical and mechanical behaviour, plasma indices and performance in Japanese quails.…”

Salmonella Enteritidis in shell eggs: Current issues and prospects for control

“…McReynolds et al (2006) determined that 100% alfalfa diets as well as diets of 70% alfalfa with 30% standard layer ration reduced colonization of the ceca with S. Enteritidis. Dunkley et al (2007c) orally challenged hens on different molting diets and determined that there was a reduction of colonization by S. Enteritidis when hens were fed 100% alfalfa crumbles as compared to feed withdrawal. There was also an increase in the expression of the hilA gene, a virulence gene of Salmonella in the feed withdrawal group as compared to alfalfa crumbles (Dunkley et al, 2007c).…”