Evaluation of Salmonella enteritidis in molting hens after administration of an experimental chlorate product (for nine days) in the drinking water and feeding an alfalfa molt diet

Salmonella Enteritidis infection, corticosterone levels, performance and egg quality in laying hens submitted to different methods of molting

In commercial layer poultry farming, molt induction is an important tool used by egg producers to prolong the production cycle of laying hens. Conventional molt induction programs involve total feed withdrawal, which raises questions about animal welfare and increased infection susceptibility. The high incidence of paratyphoid salmonellosis infections in commercial poultry farming is still an important health challenge because in addition to affecting the birds, such infections also cause public health problems. In this context, experiments were performed with laying hens at 79 wk of age to compare the conventional forced molting method (fasting) with an alternative method (free wheat bran supply) and determine their effect on the persistence of vaccine antibodies against Newcastle disease, the control and reduction of experimentally inoculated Salmonella Enteritidis, and the performance and egg quality of hens. A reduction (P < 0.05) of Salmonella Enteritidis in the crop and lower production of corticosterone were observed in the birds that received wheat bran compared with those subjected to total fasting. Moreover, a better performance (P < 0.05) with regard to egg production, egg mass, and feed conversion/kg and dozen eggs was observed in the hens that received the alternative treatment compared to the conventional forced molting method. Thus, the use of wheat bran for forced molting was found to be feasible and met the welfare needs of the hens.

Application of Molecular Approaches for Understanding Foodborne Salmonella Establishment in Poultry Production

Salmonellosis in the United States is one of the most costly foodborne diseases. Given that Salmonella can originate from a wide variety of environments, reduction of this organism at all stages of poultry production is critical. Salmonella species can encounter various environmental stress conditions which can dramatically influence their survival and colonization. Current knowledge of Salmonella species metabolism and physiology in relation to colonization is traditionally based on studies conducted primarily with tissue culture and animal infection models. Consequently, while there is some information about environmental signals that control Salmonella growth and colonization, much still remains unknown. Genetic tools for comprehensive functional genomic analysis of Salmonella offer new opportunities for not only achieving a better understanding of Salmonella pathogens but also designing more effective intervention strategies. Now the function(s) of each single gene in the Salmonella genome can be directly assessed and previously unknown genetic factors that are required for Salmonella growth and survival in the poultry production cycle can be elucidated. In particular, delineating the host-pathogen relationships involving Salmonella is becoming very helpful for identifying optimal targeted gene mutagenesis strategies to generate improved vaccine strains. This represents an opportunity for development of novel vaccine approaches for limiting Salmonella establishment in early phases of poultry production. In this review, an overview of Salmonella issues in poultry, a general description of functional genomic technologies, and their specific application to poultry vaccine developments are discussed.

Chemical treatment of animal feed and water for the control of Salmonella

The control of Salmonella in animal feedstuffs is important, principally to protect the human food chain from contamination by Salmonella derived from infected animals. The transmission of Salmonella from animal feeds to animals, and onward to human food products, has been convincingly documented. This is especially important for chicken breeding and laying flocks and pigs, in view of the consequences of recent or imminent control legislation in the European Union. Animal feed ingredients, particularly animal and plant-derived protein meals, are frequently contaminated with Salmonella either from source or from processing plant, and recontamination in compounding mills is an additional problem. Several complementary strategies have been used to control this feed contamination, and these include a range of chemical treatments. The principal agents used are as follows: organic acids and their salts, formaldehyde, and bacterial membrane disruptors such as terpenes and essential oils. Experimental agents include chlorate compounds. Many products use blends of agents from the same or different chemical groups to achieve synergistic or combination effects. The present review draws upon published and company data to describe the various modes of action and efficacies of different chemical agents delivered in feed or in drinking water against Salmonella occurring in feed or in livestock environments. Reasons for the failure of protection are explored, along with problems in usage such as corrosion and reduced palatability. Given the wide array of products available with contrasting modes of action, the need for standardized tests of efficacy is also discussed.

The effects of alfalfa-based molt diets on skeletal integrity of white leghorns

Sixty White Leghorn hens were assigned to 1 of 6 treatments: pretrial control (PC), full fed (FF), 9-d feed withdrawal (FW), 90% alfalfa-10% layer ration (A90), 80% alfalfa-20% layer ration (A80), and 70% alfalfa/30% layer ration (A70). For the PC, hens were killed and bones collected immediately before light restriction. The FF hens were also subjected to light restriction. After hens were fasted or fed different molting treatment diets for 9 d, they were fed a maintenance diet for 14 d. At 23 d postmolt, hens were killed and bones collected. Feed intakes per hen of the FF, A90, A80, and A70 treatments during a 9-d molting period were 97, 17, 44, and 46 g, respectively. Tibia dry weight of the PC was greater than the FF group. The PC group had significantly greater tibia ash weight than the FF, FW, A90, and A80 groups. Tibia ash concentration of the PC group was significantly greater than the FF, A90, and A80 groups. Humerus dry weights of the PC group were greater than the other groups except for hens on FW. Humerus ash weight was lower for FF hens as compared with PC hens, but other molting treatments had humerus ash weights similar to PC hens. Tibia mineral content and density of the PC were significantly greater than the other treatments. The FF group exhibited significantly lower humerus mineral content and density compared with those of the PC group. The PC and A70 hens exhibited significantly greater ultimate bending moment and ultimate stress compared with the FF and A90 hens. The modulus of elasticity of the PC hens was greater than that of the FF and A90. There were no significant differences in modulus of elasticity among the PC, FW, A80, and A70 hens. In conclusion, hens at 23 d postmolt experienced deterioration in skeletal integrity. This decrease in bone quality occurred in all molted hens. However, A70 and A80 alfalfa-fed hens retained mechanical properties of bones compared with the pretrial control.

In vitro fermentation response of laying hen cecal bacteria to combinations of fructooligosaccharide prebiotics with alfalfa or a layer ration

The objective of this in vitro study was to evaluate the effects of combining a prebiotic with alfalfa on fermentation by laying hen cecal bacteria. Cecal contents from laying hens were diluted to a 1:3,000 concentration with an anaerobic dilution solution and added to serum tubes filled with ground alfalfa or a layer ration with or without fructooligosaccharide (FOS) prebiotic. Samples were processed in an anaerobic hood, pressurized by using a pressure manifold, and incubated at 37 degrees C. Volatile fatty acid (VFA) and lactic acid concentrations were quantified at 6 and 24 h of substrate fermentation. In this study, fermentation of alfalfa resulted in greater production of acetate, VFA, and lactic acid compared with the layer ration. Although with a relative inconsistency in data between trials, the amendment of FOS to both alfalfa and the layer ration appeared to further increase fermentation as demonstrated by overall higher propionate, butyrate, VFA, and lactic acid concentrations. The effect was more pronounced after 24 h of fermentation, implying time constraints for the optimal production of fermentation products in the chicken gastrointestinal tract. These data indicate that in vitro cecal fermentation can be enhanced by the addition of FOS.

The influence of a fructooligosaccharide prebiotic combined with alfalfa molt diets on the gastrointestinal tract fermentation, Salmonella enteritidis infection, and intestinal shedding in laying hens

Molting is a natural process, which birds undergo to rejuvenate their reproductive organs. The US poultry egg production industry has used feed withdrawal to effectively induce molt; however, susceptibility of Salmonella Enteritidis has encouraged the development of alternative methods. Previous research conducted in our laboratory showed that alfalfa is effective at molt induction and provides equivalent postmolt production numbers and quality when compared with feed withdrawal. In the attempt to further increase the efficacy of alfalfa molt diet and decrease the chicken susceptibility to Salmonella Enteritidis during molt, fructooligosaccharide (FOS) was added to a combination of 90% alfalfa and 10% layer ration in 2 levels (0.750 and 0.375%). Ovary and liver colonization by Salmonella Enteritidis in 3 and 2 of the 4 trials, respectively, were reduced (P <or= 0.05) in hens fed FOS-containing diets compared with hens subjected to feed withdrawal. Significant decreases in ce-cal Salmonella Enteritidis counts were also observed in 2 of the 4 trials. In 3 of the 4 trials, the same diets did not affect (P > 0.05) the production of cecal total volatile fatty acids when compared with hens undergoing feed withdrawal. However, in all 3 alfalfa molt diets, the concentrations of lactic acid were greater (P <or= 0.05) than hens with feed withdrawal, but no differences (P > 0.05) were observed among hens fed alfalfa combined with FOS and hens fed alfalfa/layer ration without FOS. Overall, given the similarities between hens fed 0.750% FOS (H) and 0.375% FOS (L), molt diets combined with the lower level of FOS should be sufficient.

Fate of chlorate present in cattle wastes and its impact on Salmonella Typhimurium and Escherichia coli O157:H7

Chlorate salts are being developed as a feed additive to reduce the numbers of pathogens in feedlot cattle. A series of studies was conducted to determine whether chlorate, at concentrations expected to be excreted in urine of dosed cattle, would also reduce the populations of pathogens in cattle wastes (a mixture of urine and feces) and to determine the fate of chlorate in cattle wastes. Chlorate salts present in a urine-manure-soil mixture at 0, 17, 33, and 67 ppm had no significant effect on the rates of Escherichia coli O157:H7 or Salmonella Typhimurium inactivation from batch cultures. Chlorate was rapidly degraded when incubated at 20 and 30 degrees C with half-lives of 0.1 to 4 days. Chlorate degradation in batch cultures was slowest at 5 degrees C with half-lives of 2.9 to 30 days. The half-life of 100 ppm chlorate in an artificial lagoon system charged with slurry from a feedlot lagoon was 88 h. From an environmental standpoint, chlorate use in feedlot cattle would likely have minimal impacts because any chlorate that escaped degradation on the feedlot floor would be degraded in lagoon systems. Collectively, these results suggest that chlorate administered to cattle and excreted in wastes would have no significant secondary effects on pathogens present in mixed wastes on pen floors. Lack of chlorate efficacy was likely due to low chlorate concentrations in mixed wastes relative to chlorate levels shown to be active in live animals, and the rapid degradation of chlorate to chloride at temperatures of 20 degrees C and above.

Behavioral responses of laying hens to different alfalfa-layer ration combinations fed during molting

Induced molting by feed withdrawal has been a common practice in the commercial layer industry and usually involves the removal of feed for a period of up to 14 d. However, this is a practice that is believed to adversely influence the welfare of the hens and there is a need to examine behavioral responses to alternative molt regimens. The behavioral patterns of hens on 90% alfalfa:10% layer ration, 80% alfalfa:20% layer ration, and 70% alfalfa:30% layer ration molt diets were compared with feed withdrawal (FW) hens, and fully fed (FF) hens. The White Leghorn laying hens were approximately 54 wk old and were placed in 3 identical climate-controlled rooms. The hens were individually housed in 2-tier wire battery cages and provided treatment rations and water ad libitum. Nonnutritive pecking, walking, drinking, feeder activity, preening, aggression, and head movement were quantified during two 10-min periods each day for 6 hens from each treatment. Over the 9-d treatment period, hens in the FW, 70% alfalfa:30% layer ration, and 80% alfalfa:20% layer ration groups spent significantly more time walking than hens in the 90% alfalfa:10% layer ration group. The FF and 70% alfalfa:30% layer ration hens spent half as much time preening, whereas the FW hens displayed nearly twice as much nonnutritive pecking when compared with other treatments. Most differences in head movements occurred at the beginning of the molt period, whereas during the last half of molt, alfalfa-fed hens exhibited feeder activity similar to FF hens, and all were significantly higher than that of FW hens. After some initial adjustment by the hens, consumption of alfalfa molt diets appeared to reduce nonnutritive pecking behavior, which is characteristically associated with FW hens.

Influence of exogenous melatonin administration on Salmonella enteritidis colonization in molted layers

Two studies were conducted to evaluate the effects of melatonin on Salmonella Enteritidis infection in experimentally challenged laying hens subjected to a forced molt. Leghorn hens (>50 wk of age) were randomly assigned to rooms, acclimated to a 16L:8D regimen, and provided ad libitum access to a nonmedicated mash layer diet and water. Birds in one room were molted (8L:16D; complete feed withdrawal), whereas birds in the second room served as nonmolted controls (CONT). Within each room, birds were randomly assigned to melatonin treatment (MEL; 12 birds/treatment), dosed orally commencing the same day as feed withdrawal for 10 d: (experiment I: 0 or 5 mg of melatonin; experiment II: 0, 10, or 20 mg of melatonin). Three days following feed withdrawal, all birds were experimentally infected with Salmonella Enteritidis, and after 10 d of feed withdrawal, all birds were killed and necropsied. In experiment I, concentrations of Salmonella Enteritidis in the cecal contents and the number of Salmonella Enteritidis-positive tissues from the crop, ceca, liver, spleen, and ovary were higher (P < 0.0001) in the MOLT compared with the CONT treatments. No differences (P > 0.10) were observed in any of the parameters examined due to MEL treatment. For experiment II, cecal concentrations of Salmonella Enteritidis were generally higher in the MOLT compared with the CONT treatment and within molted birds, cecal concentrations were higher in the MEL treatment (P < 0.05). Melatonin treatment in molted birds increased (P < 0.05) the percentage of positive crops in the MOLT+20 MEL treatment (P < 0.05). Salmonella-positive cecal tissue was increased (P < 0.001) in MOLT compared with CONT birds and was also higher in MOLT+10 MEL and MOLT+20 MEL birds compared with the MOLT-only treatment. Results from the current research suggest that dosage with high levels of melatonin may exacerbate Salmonella Enteritidis infection in layers subjected to forced molt.

Behavior of laying hens on alfalfa crumble molt diets

Several dietary alternatives to feed withdrawal have been proposed to induce a molt in laying hens. This study compared the behavior of laying hens on an alfalfa crumble diet (ALC) to hens that were either on a conventional layer diet (FF) or hens that had feed withdrawn (FW) during a 9-d trial. Each treatment consisted of 24 hens (3 hens per battery cage), and treatment began after a 2-week acclimation period. Video cameras connected to a digital multiplexer recorded the behavior of the hens. The percentages of observations performing nonnutritive pecking, feeder activity, drinking, walking, preening, head movement, and aggression were quantified for two 10-min periods at daily intervals. The FF hens spent significantly more (P < or = 0.05) time drinking than the other treatments, whereas FW hens displayed the most head movements. From d 1 through 7, FW hens walked less than ALC hens except on d 8 when FW hens walked more than ALC and FF hens. On d 4 and 6, the FW hens spent an increased amount of time preening compared with FF hens until the last few days of the molt period. For the most part, FW hens generally displayed more nonnutritive pecking than ALC and FF hens throughout the molt period. However, FW hen visits to the feeders declined as the trial proceeded, whereas ALC and FF hens generally spent more time at the feeder. In summary, the ALC diet showed potential as an alternative to FW for inducing a molt in laying hens based on reduced nonnutritive pecking behavior, head movements, and greater feeding activity.

Foodborne Salmonella ecology in the avian gastrointestinal tract

Foodborne Salmonella continues to be a major cause of salmonellosis with Salmonella Enteritidis and S. Typhimurium considered to be responsible for most of the infections. Investigation of outbreaks and sporadic cases has indicated that food vehicles such as poultry and poultry by-products including raw and uncooked eggs are among the most common sources of Salmonella infections. The dissemination and infection of the avian intestinal tract remain somewhat unclear. In vitro incubation of Salmonella with mammalian tissue culture cells has shown that invasion into epithelial cells is complex and involves several genetic loci and host factors. Several genes are required for the intestinal phase of Salmonella invasion and are located on Salmonella pathogenicity island 1 (SPI 1). Salmonella pathogenesis in the gastrointestinal (GI) tract and the effects of environmental stimuli on gene expression influence bacterial colonization and invasion. Furthermore, significant parameters of Salmonella including growth physiology, nutrient availability, pH, and energy status are considered contributing factors in the GI tract ecology. Approaches for limiting Salmonella colonization have been primarily based on the microbial ecology of the intestinal tract. In vitro studies have shown that the toxic effects of short chain fatty acids (SCFA) to some Enterobacteriaceae, including Salmonella, have resulted in a reduction in population. In addition, it has been established that native intestinal microorganisms such as Lactobacilli provide protective mechanisms against Salmonella in the ceca. A clear understanding of the key factors involved in Salmonella colonization in the avian GI tract has the potential to lead to better approach for more effective control of this foodborne pathogen.

Immunological cell and serum metabolite response of 60-week-old commercial laying hens to an alfalfa meal molt diet

The practice of induced molting involves the restriction of light, feed removal and optionally water for 5-14 days. However, there is growing concern regarding feed removal and animal welfare issues. With this in mind, alternative diets have been developed to produce similar molting effects as that of feed deprivation. Alfalfa, which largely consists of insoluble fiber, can be used as a molting diet. In this study, heterophil and lymphocyte counts, serum chemistry, and organ weight parameters were evaluated in hens that were deprived of feed or fed alfalfa during a nine day induced molt. Full-fed hens were used as the control. Blood serum parameters assessed included calcium, magnesium, glucose, total protein, ketone bodies, uric acid, and cholesterol. White blood cells were counted and categorized by cell type. On the ninth day of the trial, the hens were euthanized and the liver, spleen, heart, intestine, pancreas, ovary, oviduct, and kidney were collected and weighed. On day 8 birds molted with alfalfa or by feed deprivation had significantly higher (P<0.05) levels of ketone bodies and cholesterol and lower levels of calcium, and magnesium compared to the full-fed hens while birds molted by feed deprivation exhibited significantly lower levels of uric acid. Birds molted by both methods exhibited significant reductions in ovary, oviduct, liver and pancreas weights and increased spleen weights when compared to the non-molted hens. On days 0, 2, and 6 there were no significant differences (P>0.05) in either heterophil or lymphocyte percentages. However, heterophil percentages were higher in feed withdrawal birds than full-fed birds on day 4 but lymphocyte percentages were higher in full-fed birds compared to feed withdrawal birds. On day 8 of the induced molt lymphocyte percentages were higher from full-fed birds when compared to feed withdrawal birds but no significant differences were detectable for heterophil percentages. Based on reproductive organ weight loss and changes in serum and immunological responses of birds during molt, it appears that alfalfa meal can be an effective molt induction alternative.

Molting in Salmonella enteritidis-challenged laying hens fed alfalfa crumbles. IV. Immune and stress protein response

Immunological responses of molting hens either infected or not infected with Salmonella enterica serovar Enteritidis were compared in 2 trials with Single Comb White Leghorn hens >50 wk old. The hens were placed into 6 treatment groups with 12 hens per group: nonmolted Salmonella Enteritidis positive (FF+), non-molted Salmonella Enteritidis negative (FF-), feed withdrawal Salmonella Enteritidis positive (FW+), FW Salmonella Enteritidis negative (FW-), alfalfa Salmonella Enteritidis positive (ALC+), and ALC Salmonella Enteritidis negative (ALC-). Each hen in the Salmonella Enteritidis-positive groups was challenged on d 4 of the study with 1 mL of 10(6)-cfu Salmonella Enteritidis, and diets were administered for 12 d. Blood samples were collected on d 2, 5, 9, and 12, and blood smears were enumerated for heterophil to lymphocyte (H:L) ratios. Serum samples were also analyzed for alpha(1)-acid glycoprotein (AGP) levels and antibody level. On d 12, hens were euthanized and bile samples from the gall bladder and sections of the ileum and the ceca were collected, and an ELISA was used to determine the intestinal, serum, and bile antibody responses. The FW+ hens produced more (P <or= 0.05) cecal IgA than hens in all the other treatments except the FW-hens in trial 2. Bile IgA production in all Salmonella Enteritidis-positive groups was higher (P <or= 0.05) than in the Salmonella Enteritidis-negative groups, with the exception of the ALC- hens. In trial 1 on d 5, FW+ hens produced less (P <or= 0.05) serum IgG than ALC-, FF-, and FW- hens but not FF+ and ALC+ hens, whereas in trial 2, only FW- hens had lower IgG levels than FW+ hens. On d 9, FW groups exhibited increases in the H:L ratios, but on d 12, these declined to levels more similar to the other treatments. The FW hen groups yielded generally higher AGP levels compared with the other treatments on d 9 and 12 in both trials. The ALC molt diets appeared to reduce stress and inflammation, based on the H:L ratios and AGP levels in the serum, when compared with FW-molted hens.

Molting in Salmonella enteritidis-challenged laying hens fed alfalfa crumbles. III. Blood plasma metabolite response

The objective of this study was to examine an alfalfa crumble diet as an alternative molt diet and compare the physiological response of hens to the responses of feed-deprived molted hens. Hens >50 wk old were placed into 6 treatment groups (12 hens per group in trial 1 and 10 hens per group in trial 2): nonmolted Salmonella enterica serovar Enteritidis positive (FF+), nonmolted Salmonella Enteritidis negative (FF-), feed withdrawal Salmonella Enteritidis positive (FW+), FW Salmonella Enteritidis negative (FW), alfalfa Salmonella Enteritidis positive (ALC+), and ALC Salmonella Enteritidis negative (ALC-). Each hen in the Salmonella Enteritidis-positive groups was challenged on the fourth day of the study with 1 mL of 10(6)-cfu Salmonella Enteritidis. Blood was collected on d 2, 5, 9, and 12 of the trial. Blood plasma was collected and metabolite concentrations were analyzed for glucose, calcium, cholesterol, uric acid, total protein, and triglycerides. The feed intakes of the FF hens were 4- to 6-fold greater (P <or= 0.05) than those of the ALC birds in both trials. Over the 12 d of molt, the FW+ hens lost more (P <or= 0.05) BW than all other groups except the FW- hens, whereas the FW-, ALC-, and ALC+ hens lost more BW than the FF hen groups. Uric acid concentrations were generally lower in molted hens compared with the FF hen groups during the initial stages of molt. On d 9 of both trials, concentrations of calcium and total protein were higher (P <or= 0.05) in the FF hens than in the other groups. The FF hen groups exhibited higher (P <or= 0.05) concentrations of triglycerides than the FW and ALC groups in both trials on d 5, 9, and 12. Based on the results from these studies, ALC diets can limit some of the potential physiological stress indicators that accompany feed deprivation during an induced molt.

Molting in Salmonella Enteritidis-challenged laying hens fed alfalfa crumbles. II. Fermentation and microbial ecology response

The objective of this study was to examine microbial population shifts and short-chain fatty acid (SCFA) responses in the gastrointestinal tract of Salmonella Enteritidis-challenged molted and nonmolted hens fed different dietary regimens. Fifteen Salmonella-free Single Comb Leghorn hens (>50 wk old) were assigned to 3 treatment groups of 5 birds each based on diet in 2 trials: 100% alfalfa crumbles (ALC), full-fed (FF, nonmolted) 100% commercial layer ration, and feed withdrawal (FW). A forced molt was induced by either a 12-d alfalfa diet or FW. In all treatment groups, each hen was challenged by crop gavage orally 4 d after molt induction with a 1-mL inoculum containing 10(6) cfu of Salmonella Enteritidis. Fecal and cecal samples (d 4, 6, 8, 11, and necropsy on d 12) were collected postchallenge. Microbial population shifts were evaluated by PCR-based 16S ribosomal RNA gene amplification and denaturing gradient gel electrophoresis, and SCFA concentrations were measured. Total SCFA in fecal and cecal contents for FW molted hens were generally lower (P < or = 0.05) in the later stages of the molt period when compared to ALC and FF treatment groups. The overall trend of SCFA in cecal and fecal samples exhibited similar patterns. In trials 1 and 2, hens molted with ALC diet generally yielded more similar amplicon band patterns with the FF hens in both fecal and cecal samples by the end of the molting period than with FW hens. The results of these studies suggest that ALC molted hens supported microflora and fermentation activities, which were more comparable to FF hens than FW hens by the end of the molting period.

Molting in Salmonella enteritidis-challenged laying hens fed alfalfa crumbles. I. Salmonella enteritidis colonization and virulence gene hilA response

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.

Total radioactive residues and residues of [36Cl]chlorate in market size broilers

The oral administration of chlorate salts reduces the numbers of Gram-negative pathogens in gastrointestinal tracts of live food animals. Although the efficacy of chlorate salts has been demonstrated repeatedly, the technology cannot be introduced into commercial settings without first demonstrating that chlorate residues, and metabolites of chlorate remaining in edible tissues, represent a negligible risk to consumers. Typically, a first step in this risk assessment is to quantify the parent compound and to identify metabolites remaining in edible tissues of animals treated with the experimental compound. The objectives of this study were to determine the pathway(s) of chlorate metabolism in market broilers and to determine the magnitude of chlorate residues remaining in edible tissues. To this end, 12 broilers (6 weeks; 2.70+/-0.34 kg) were randomly assigned to three treatments of 7.4, 15.0, and 22.5 mM sodium [36Cl]chlorate dissolved in drinking water (n=4 broilers per treatment). Exposure to chlorate, dissolved in drinking water, occurred at 0 and 24 h (250 mL per exposure), feed was withdrawn at hour 38, water was removed at hour 48, and birds were slaughtered at hour 54 (16 h after feed removal and 8 h after water removal). The radioactivity was rapidly eliminated in excreta with 69-78% of the total administered radioactivity being excreted by slaughter. Total radioactive residues were proportional to dose in all edible tissues with chloride ion comprising greater than 98.5% of the radioactive residue for the tissue (9.4-97.8 ppm chlorate equivalents). Chlorate residues were typically greatest in the skin (0.33-0.82 ppm), gizzard (0.1-0.137 ppm), and dark muscle (0.05-0.14 ppm). Adipose, liver, and white muscle tissue contained chlorate concentrations from 0.03 to 0.13 ppm. In contrast, chlorate concentrations in excreta eliminated during the 6 h period prior to slaughter ranged from 53 to 71 ppm. Collectively, these data indicate that broilers rapidly convert chlorate residues to an innocuous metabolite, chloride ion, and that chlorate residues in excreta remain fairly high during the time around slaughter. Because the target tissue of chlorate is the lower gastrointestinal tract, the relatively high distribution of parent chlorate to inedible gastrointestinal tissues and low distribution to edible tissues is favorable for the biological activity and for food safety considerations. These data, when used in conjunction with a toxicological assessment of chlorate, can be used to determine a likely risk/benefit ratio for chlorate.

In vitro anaerobic incubation of Salmonella enterica serotype Typhimurium and laying hen cecal bacteria in poultry feed substrates and a fructooligosaccharide prebiotic

The objective of this study was to investigate the effect of combining a prebiotic with poultry feeds on the growth of Salmonella enterica serotype Typhimurium (ST) in an in vitro cecal fermentation system. Cecal contents from three laying hens were pooled and diluted to a 1:3000 concentration in an anaerobic dilution solution. The cecal dilution was added to sterile test tubes filled with alfalfa and layer ration with and without fructooligosaccharide (FOS). Two controls containing cecal dilutions and anaerobic dilution solution were used. The samples were processed in the anaerobic hood and incubated at 37 degrees C. Samples were inoculated with Salmonella at 0 and 24h after in vitro cecal fermentation and plated at 0 and 24h after inoculation with ST. Plates were incubated for 24h and colony forming units (CFU) enumerated. The samples immediately inoculated with ST without prior cecal fermentation did not significantly lower ST counts 24h later. However, samples pre-incubated for 24h with cecal microflora prior to ST inoculation exhibited reduced ST CFU by approximately 2 logarithms, with the most dramatic decreases seen in alfalfa and layer ration combined with FOS. The addition of FOS to feed substrate diets in combination with cecal contents acted in a synergistic manner to decrease ST growth only after ST was introduced to 24h cecal incubations.