A. Salmonella virulence expression in molted birds, objectives are 1) to determine if addition of dietary moderate zinc-low calcium will prevent colonization of Salmonella Enteritidis in the crop of chickens undergoing molting and what characteristics in the crop microenvironment are associated with this type of induced molt, and 2) to understand the potential role of that crop for Salmonella Enteritidis virulence expression while birds are undergoing molting and if key characteristics in the chicken crop microenvironment can be linked with limiting S. Enteritidis colonization and virulence expression.
<P> B. The role of methanogens in establishment of anaerobic microflora, the objectives are 1) to determine when methanogens become a part of the cecal microflora, what characteristics in the cecal microenvironment are associated with establishment of methanogens and enumerate the methanogen populations, and 2) to determine how stable the cecal methanogen population is by looking at whether feed deprivation alters methanogen activity while birds are undergoing fasting and if key characteristics in the chicken cecal microenvironment can be linked with decreased methanogen populations. <P>
The hypothesis is that the final stages of cecal opligate anaerobic microfloral development will coincide with the emergence of methanogens and their presence will signify completion of establishment of the dynamic complex anaerobic population characteristic of mature birds. In addition, we hypothesize that decreases in numbers of mathanogens signifies the beginning of instability in the cecal anaerobic microflora.
NON-TECHNICAL SUMMARY: Specific research plans reflect an integrated approach for controlling Salmonella in the early stages of production of poultry. This project will provide A)ideas for management alternatives to reduce molting as a risk for S. Enteritidis contamination, and B) understanding of the role of methanogens in the development of the cecal microflora, the natural microflora being inhibitory to Salmonella.
APPROACH: A. Salmonella virulence expression in molted birds: the idea here is to compare the indigenous microbial response in crops of birds that have been molted either by feed deprivation or using the moderate Zn diet approach. The hypothesis is that feed intake will be retained in the birds molted via moderate Zn addition and the crop microflora will continue to be actively fermenting to the point of being inhibitory to Salmonella Enteritidis colonization and invasion. Based on our earlier work we hypothesize that the key indicators of an active fermentation in the crop are low pH and a high concentration of lactate. Therefore, in addition to enumerating Salmonella Enteritidis recovered after infection in the different treatment groups we plan to thoroughly examine the microenvironment of the crops from the birds in these different treatment groups. This will be done by quantitating fermentation products and enumeration of the crop lactobacilli. Whether these key characteristics in the chicken crop microenvironment can be linked with limiting S. Enteritidis in vivo invasion will be determined by examining virulence activity of Salmonella Enteritidis (hilA-lacZY trancriptional operon fusion) with a gene fusion strain for in vitro assays of crop contents. B. The role of methanogens in establishment of anaerobic microflora: The overall experimental concept in this proposal is to determine when methanogens appear in the ceca as birds age on different diets and how stable the methanogen population is during drastic dietary changes. To accomplish this, methanogens will be enumerated from three different scenarios: 1) newly hatched chicks on different diets; 2) newly hatched chicks given a cecal transfer from adult birds and 3) feed deprived molted laying hens. These three scenarios represent the commercial settings where the cecal microflora are considered important in resisting colonization by foodborne pathogens, namely, young chicks with or without a probiotic and laying hens undergoing molting. In the proposed work we plan to thoroughly examine the microenvironment of the ceca in the three groups of birds. This will done by quantitating fermentation products (VFA, lactate, pH, and Eh) and in addition to quantifying methanogens, enumerate microbial components of the ceca including lactobacilli, bifidobacteria, Escherichia coli, total aerobic and anaerobic bacteria. The rationale for these choices is that aerobic bacteria and E. coli represent facultative populations that are generally early colonizers of the chick ceca, followed by lactobacilli and bifidobacteria and finally the strict anaerobes. These subgroups of organisms in addition to the fermentation products should give us a representative profile of the microbial population changes occurring in the ceca prior to and during the establishment of methanogens. Whether these characteristics in the chicken cecal microenvironment can be linked with establishment of methanogens will be the outcome of this component of the proposal.
PROGRESS: 2001/05 TO 2006/05<BR>
During the past decade, the number of cases of gastroenteritis due to Salmonella enterica serovar Enteritidis (SE) infections has continued to increase in the United States. SE is invasive in poultry and therefore has the potential to contaminate eggs by transovarian transmission following colonization of the intestinal tract. Periodic clusters of contaminated eggs produced by laying hens may be related to stress incurred from specific management practices such as molting. Feed withdrawal is the primary method used in the layer industry to induce molting and stimulate multiple egg-laying cycles in hens. The stress associated with feed withdrawal, decreases fermentation in the gut, and increases SE organ invasion. Ideally, a molting approach is needed by the poultry industry that is as easy as simple feed deprivation but avoids the disruption of the protective microflora in the gastrointestinal tract and promotion of physiological stress to the bird during molting. We believed that the key to inducing a molt that minimizes pathogen infection and stress of laying hens was to use a low energy molt diet that not only supported optimal egg production but maximizes gut bacterial fermentation activities antagonistic to pathogens. An alternative alfalfa molt diet initially developed by us at Texas A&M University was demonstrated to limit SE colonization and bird stress during molting. Although our data suggested that 100 % ad libitum alfalfa diets would potentially limit SE colonization, the detectable SE levels in some birds suggested an inconsistency in the promotion of gut microflora antagonistic to SE. Therefore we examined different physical forms (ground meal versus crumble) of our alfalfa molting diet and either combined with layer ration (90 % alfalfa + 10% layer ration), a prebiotic (fructooligosaccharide, FOS + 100% alfalfa) or an antimicrobial dietary supplement (experimental chlorate product (ECP + 100% alfalfa). Our key results for this Hatch project were as follows:(1) Alfalfa in all physical forms (meal and crumble) and alfalfa + layer ration stopped egg production and effectively initiated molt induction while birds continued to consume diet. (2) Alfalfa + layer ration limited stress in laying hens during molt when measured as behavior and physiological responses. (3) Alfalfa + layer ration retained similar post molt egg production numbers and egg quality parameters as feed withdrawal. (4) Alfalfa + layer ration, alfalfa + FOS and alfalfa + ECP all minimized colonization of S. Enteritidis in susceptible laying hens during molting. The results of these studies provided the poultry industry with several alfalfa molt diet combinations as practical alternatives to feed deprivation induced molting that would minimize Salmonella infestations in layer flocks and reduce physiological stress to the bird.
IMPACT: 2001/05 TO 2006/05<BR>
Salmonellosis continues to be one of the more prevalent foodborne diseases in poultry. Controlling and limiting the spread of an organism in preharvest in paramount to decreasing occurrence of the organism in poultry products and eggs.