Induction of cadBA in an Escherichia coli lysine auxotroph transformed with a cad-gfp transcriptional fusion.

CadBA functions as a part of overall Escherichia coli response to low extracellular pH. A gfpmut3 structural gene transcriptionally fused to the cadBA promoter (Pcad) was used as a reporter to monitor changes in intracellular lysine as a potential factor influencing cadBA induction. Different patterns of cadBA induction were observed in two E. coli strains with different lysine biosynthetic capabilities. In E. coli ZK126 (pJBA25-Pcad), a lysine prototroph, maximum levels of induction were detected 3 h after the transfer of bacterial cells under inducing conditions (pH 5.8; 3.4 microM extracellular lysine). The induction subsequently decreased until hour 7 after which no further change in expression was observed. However, in the lysine depleted strain E. coli ATCC 23812 (pJBA25-Pcad) which is an auxotroph for lysine, no decrease in cadBA expression was observed over time under the same induction conditions. Although no time dependent statistical differences in intracellular lysine were observed, bacterial cells depleted for no longer than 4 h (1.38 +/- 0.25 micromol lysine/g cell dry weight) exhibited more rapid induction of cadBA (after 3 h) and a lower maximum level of induction compared to cells with relatively lower intracellular lysine (approximately 1.08 micromol/g cell dry weight). For the latter, the detectable level of induction was delayed for 1 h but the maximum level of induction response was higher.

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 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 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.

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.

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.

A cad-gfpmut3 plasmid construct in Escherichia coli for gene induction-based quantification of lysine in acid hydrolysates of feedstuffs.

AIMS: To generate an inducible plasmid-borne cad-gfpmut3 transcriptional fusion and develop a method for quantification of total lysine. METHODS AND RESULTS: The cad-gfpmut3 transcriptional fusion was constructed by cloning the cad promoter (Pcad) upstream of a promotorless gfpmut3 located on a high-copy plasmid. The construct was electroporated into Escherichia coli ZK126 and the transformed strain was subsequently used to quantify lysine in feed ingredients. Lysine standard curves based on gene induction of the bacterial cells were used for estimating acid hydrolysate lysine concentrations in four feed ingredients. Except for sorghum, no substantial differences were observed when the data for lysine in soybean (2 x 49 +/- 0 x 37%), cottonseed (1 x 82 +/- 0 x 15%), and meat and bone meal (2 x 31 +/- 0 x 24%) generated by the newly developed construct were compared with previously published data. CONCLUSIONS: Using the cad-gfpmut3 fusion, feed derived lysine induction was measured easily and accurately, and could be a useful tool for the estimation of lysine in acid hydrolysates of feed ingredients. SIGNIFICANCE AND IMPACT OF THE STUDY: The described approach for lysine quantification in feed ingredients represents a cost- and time-efficient method offering rapid and accurate lysine quantification of multiple samples.

Detection of methane and quantification of methanogenic archaea in faeces from young broiler chickens using real-time PCR.

AIMS: To detect the presence of methanogens in the faeces of broiler chicks during the first 2 weeks of age. METHODS AND RESULTS: Chicken faecal samples from 120 broiler chicks were incubated for methane gas formation and methanogenic archaea were analysed using real-time PCR. The copy number of the order Methanobacteriales 16S rDNA gene in chicken faeces when the broilers were 3-12 days of age, litter and house flies collected in the bird house ranged from 4.19 to 5.51 log(10) g(-1) wet weight. The number of positive methane culture tubes increased from 25% to 100% as the birds aged. CONCLUSIONS: Methanogens were successfully detected in faecal samples from 3- to 12-day-old broilers, as well as litter and house flies using real-time PCR. The copy number of methanogenic 16S rDNA gene in these samples was also similar to the number observed in litter and house flies. SIGNIFICANCE AND IMPACT OF THE STUDY: The same methanogens consistently appeared in chicken faeces a few days after birth. Detection of the methanogenic bacteria in litter and house flies implicated them as potential environmental sources for methanogen colonization in broiler chicks.

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.

Quantification of total and bioavailable lysine in feed protein sources by a whole-cell green fluorescent protein growth-based Escherichia coli biosensor.

Using a fluorescent whole-cell Escherichia coli biosensor previously developed in our laboratory, we determined total and bioavailable lysine in four feed ingredients (soybean, cottonseed, meat and bone meal, and sorghum) and three complete feeds (chick starter and finisher, and swine starter). The same feed sources were analyzed for total lysine by high performance liquid chromatography (HPLC) and bioavailable lysine by chick bioassay. No significant differences were found between bioavailable lysine estimates for soybean, cottonseed, meat and bone meal, chick starter and finisher, and swine starter obtained by the fluorescent E. coli biosensor and chick bioassay. Except for sorghum, the E. coli biosensor estimates for total lysine were highly comparable to those obtained by HPLC. Comparisons were also conducted between conventionally performed optical density-based and the newly developed fluorescence-based lysine assay. The lack of significant differences in data obtained for total and bioavailable lysine by both detection modes indicated reliance and accuracy of the fluorescent E. coli biosensor. Overall results suggest that the microbial assay based on green fluorescent protein fluorescence represents a promising alternative method for lysine quantification.

Effect of various combinations of alfalfa and standard layer diet on susceptibility of laying hens to Salmonella enteritidis during forced molt.

Feed deprivation is commonly used by the poultry industry to induce molting and stimulate multiple egg-laying cycles. However, feed deprivation has been observed experimentally to increase susceptibility of poultry to Salmonella infections. Previous studies indicated that alfalfa was efficacious in reducing Salmonella; the present investigation was designed to evaluate the efficacy of combined alfalfa and layer diets on Salmonella colonization. Leghorn hens over 50 wk of age were divided into 12 groups of hens and placed in individual laying cages. One week prior to dietary changes, hens were put on an 8L:16D photoperiod that continued for the 9-d experiment. Hens were challenged orally with 104 cfu of Salmonella Enteritidis (SE) on d 4 of treatment and cultured for SE at the termination of the 9-d study. Two independent experiments were conducted consisting of the following treatment groups: nonfed hens, full-fed standard commercial layer diet, 100% alfalfa meal diet, a 90% alfalfa meal/10% standard commercial layer diet, and a 70% alfalfa meal/30% standard commercial layer diet. When evaluating SE colonization in the ceca (Exp. 1), a reduction (P < 0.05) was seen in the 100% alfalfa meal diet and the 70% alfalfa meal/30% standard commercial layer diet treatment groups when compared with the controls with Log10 values of 0.54, 0.44, and 2.82, respectively. Evaluation of physiological parameters showed the alfalfa treatment groups had reductions (P < 0.05) in weight loss, ovary weight, and feed consumption when compared with the full-fed standard commercial layer diet hens, and these results were comparable with the nonfed hens. In Exp. 2, all of the treatment groups had a reduction (P < 0.05) in SE colonization of the ceca when compared with the controls. There were also similar physiological reductions in weight loss, ovary weight, and feed consumption when birds were fed the alfalfa diets in Exp. 2. These data suggest that alfalfa can potentially be combined with layer ration to limit SE infection and still induce a molt comparable with feed withdrawal.

Application of an Escherichia coli green fluorescent protein-based lysine biosensor under nonsterile conditions and autofluorescence background.

AIMS: To examine the utility of an Escherichia coli green fluorescent protein (GFP) containing biosensor for quantification of bioavailable lysine in selected feed samples under nonsterile conditions and to estimate the background fluorescence of analyzed feed samples and evaluate the risk of confounding GFP emission from the lysine assay organism. METHODS AND RESULTS: Escherichia coli lysine auxotroph GFP based biosensor was used to determine the percentage of bioavailable lysine in two samples of soybean-, cottonseed-, and meat and bone meal under nonsterile conditions. The fluorescence emitted by GFP was successfully measured using a spectrofluorimeter to monitor bacterial growth response to protein-derived lysine and lysine containing small peptides. The autofluorescence of analyzed feed samples at different concentrations could also be estimated. CONCLUSIONS: When feed protein concentrations are decreased, autofluorescence interference can be avoided. SIGNIFICANCE: The E. coli lysine auxotroph GFP-based biosensor can successfully be used for the determination of bioavailable lysine in these selected animal feed proteins under nonsterile conditions. IMPACT OF THE STUDY: E. coli GFP biosensor for lysine has potential for routine application in animal feeds.

Utilizing different ratios of alfalfa and layer ration for molt induction and performance in commercial laying hens.

Molting is a common practice used by the commercial egg industry to rejuvenate flocks for a second or third laying cycle. During this time the hens rest from production, and the reproductive organs are rejuvenated to increase production and quality during the next laying cycle. Although feed withdrawal (FW) is the most popular and effective method of molt induction, it has come under scrutiny due to food safety issues and animal welfare issues. This study involved feeding alfalfa mixed with layer ration at different ratios to hens to determine their ability to induce molt. The treatment ratios were 100% alfalfa (A100), 90% alfalfa and 10% layer ration (A90), and 70% alfalfa and 30% layer ration (A70). In addition, a fully fed (FF) nonmolted control and a FW negative control were used. Alfalfa is an insoluble, high fiber feedstuff with low metabolizable energy. Egg production for A90 and FW treatments ceased completely by d 6, whereas birds fed A100 and A70 ceased egg production by d 8. Ovary and oviduct weight of hens fed all molting diets decreased (P < 0.05) by an average of 1.5 to 2.5% (BW basis) compared with FF control during the 9-d molt induction period. As the percentage of layer ration increased, feed intake also increased and percentage of BW loss decreased during the 9-d molt induction period. Hens molted by FW lost an average of 25.8% BW, whereas A70 hens lost 18.9% BW. Nonmolted hens (FF) and A70 treatment hens had significantly lower (P < 0.05) egg production when compared with all other treatments over the 39-wk postmolt period. FF treatment hens also had lower (P < 0.05) albumen heights when compared with all other treatments. From these results, alfalfa or alfalfa mixed with layer ration appears to be viable alternatives to conventional FW methods for the successful induction of molt and retention of postmolt performance.

Reduction of Salmonella enterica serovar enteritidis colonization and invasion by an alfalfa diet during molt in Leghorn hens.

The standard method for molting to stimulate multiple egg-laying cycles in laying hens is feed deprivation. However, the physiological changes within hens caused by feed deprivation increase susceptibility of the hens to Salmonella enterica serovar Enteritidis (SE) infection. In an effort to develop an alternative method to induce molting without increasing susceptibility to SE, an alfalfa diet was compared with the standard molting method for the level of ovary regression and SE colonization. Hens over 50 wk of age were divided into 3 treatment groups (12 hens/group): nonmolting by normal feeding (NM), molting by feed deprivation (M), and molting by alfalfa diet (A). Individual hens on all treatments were challenged orally with 10(5) cfu of SE on the fourth day after feed changes and were analyzed for ovary weight and SE colonization or invasion in crop contents, cecal contents, liver, spleen, and ovary on the ninth day. In 3 of the 4 trials, there was a significant decrease in SE colonization of the crop between the alfalfa diet (A) and the feed deprived molt (M). In most of the 4 trials, there was a significant reduction in SE infected organs in birds fed the alfalfa diet (A) compared with birds undergoing feed deprived molt (M). Most of the trials showed no significant difference in overall SE between A and NM. Therefore, the results of this study suggest that an alfalfa diet has the potential to be used as an alternative method for forced molting, without increasing the incidence of SE in eggs and internal organs.

Potential of alfalfa as an alternative molt induction diet for laying hens: egg quality and consumer acceptability.

Dietary molt induction to initiate additional egg laying cycles in commercial laying hen flocks is a wide spread practice in the United States. Feed deprivation is the most commonly used method but this practice has generated several concerns which has lead to research for viable alternative approaches. From a management standpoint a single ingredient molting diet consisting of high fiber-low energy represents an easily adaptable diet for large laying hen production units. Alfalfa meal is readily available in most commercial locations and possesses many of the desirable properties of an ideal laying hen molt diet. In the current study hens at a commercial laying facility were molted by both alfalfa and feed deprivation. After the hens had reentered post-molt commercial egg production, eggs were examined for egg quality performance. Egg shell strength, albumen height, yolk height, weight, length, and yolk color were all tested using various mechanical techniques. The eggs were also sampled for testing by consumer sensory panels that assessed the desirability of the eggs' color and flavor/texture. Eggs laid by hens molted by alfalfa had a significantly lower (p<0.05) "a*" level of colorimetry. Eggs laid by hens molted with alfalfa also exhibited significantly higher (p<0.05) egg weights and length. In the consumer sensory test, there was no significant difference (p>0.05) in color or flavor/texture scores in eggs from either feed deprived or alfalfa molted hens. The consumer sensory and mechanical quality attributes indicates that alfalfa shows promise as an alternative molt induction diet by providing a single diet option for extending egg production into a second egg laying cycle.

Alfalfa as a single dietary source for molt induction in laying hens.

Molting is a process by which a hen's reproductive tract is rejuvenated prior to the beginning of a laying cycle. This process is often artificially induced in commercial settings in order to extend the productive life of a flock of hens. The most common method for the induction of molt is feed withdrawal for a period of several days. It has been noted that feed withdrawal, while effective in inducing molt and allowing an adequate reproductive rest period for the hen, may cause deleterious effects on the animal. This has prompted the investigation of alternatives to feed deprivation for the induction of molt in commercial laying hens. This study involved feeding alfalfa to hens to assess its ability to induce molt. Results show that alfalfa meal and alfalfa pelleted diets were equally effective as feed withdrawal in causing ovary weight regression in birds. Molted hens induced by alfalfa diets exhibited postmolt levels of egg production over a twelve week period that were similar to that of hens molted by feed withdrawal. The postmolt eggs laid by hens molted by alfalfa were of comparable quality to eggs from feed deprived hens. Alfalfa, a fibrous feed with low metabolizable energy, may be provided to hens on an ad libitum basis for an effective molt induction that retains comparable egg quality and production.

Salmonella enterica serovar Typhimurium hilA-lacZY fusion gene response to iron chelation or supplementation in rich and minimal media.

Virulence expression of Salmonella enterica serovar Typhimurium under iron limited condition was measured by beta-galactosidase (beta-gal) assay using a hilA-lacZY fusion strain and calculated as Miller units. hilA-lacZY beta-galactosidase assays were performed in brain heart infusion (BHI) and minimal media (M9), after iron chelation with 2, 2-dipridyl and iron-supplementation respectively. Before performing virulence assays, concentrations of iron in the media were estimated using ferrozine. Iron content was found to be more in BHI (42.6 microg dL(-1)) as compared to M9 (10.03 microg dL(-1)). beta-gal activity of Salmonella Typhimurium in BHI was generally less than that observed in M9. After exposure to various combinations of iron chelator in BHI, hilA-lacZY activity only increased at the highest concentration of chelator (2001 microM) but decreased in M9 media for all iron concentrations when compared to controls with no iron amendment. These results indicate that iron availability may influence S. Typhimurium hilA expression.

Research note: Effects of different bone preparation methods (fresh, dry, and fat-free dry) on bone parameters and the correlations between bone breaking strength and the other bone parameters.

A study was conducted to evaluate effects of different bone preparation methods on bone parameters and the correlations between bone breaking strength and the other bone parameters. Bone breaking strength is dramatically changed depending on bone preparation methods, whereas other bone parameters such as ash content and ash concentration are not significantly influenced by bone preparation methods. Thus, the objective of this study was to evaluate the effects of 3 bone preparations (fresh, dry, and fat-free dry) on bone parameters and the relationship between bone breaking strength and bone parameters. Sixty Single Comb White Leghorn hens were used for this study. Hens were euthanized by CO2 gas, and the right tibia and femur were collected. The bones were divided into 3 treatment groups: fresh, dry, and fat-free dry. There were no significant differences in fresh weight, bone volume, dried weight, ash weight, and ash concentration of tibia and femur among the treatments. However, fresh tibia (24.13 kg) exhibited more bone breaking strength compared with the dried (9.90 kg) and fat-free dried bones (7.41 kg) (P < 0.05). The bone breaking strength (20.97 kg) of fresh femur was also significantly higher than the dried (9.22 kg) and fat-free dried femurs (6.94 kg). The bone breaking strength of the fresh bone was highly correlated with dried weight, ash weight, and ash concentration, whereas that of the fat-free dried bone was poorly correlated with the other bone parameters. The results indicate that fresh bone gives better bone breaking strength correlated to the other bone parameters than dry or fat-free dry preparation.

The combination of zinc compounds and acidic pH limits aerobic growth of a Salmonella typhimurium poultry marker strain in rich and minimal media.

The objective of the present study was to examine the combined effects of zinc compounds with different acidic pH levels on the aerobic growth of a S. typhimurium poultry isolate in either rich or minimal media. When overall main effects of pH levels of medium or concentrations of Zn compounds were compared, growth rates of the S. typhimurium poultry isolate were significantly (p < 0.05) decreased by stepwise increase of pH levels of medium (pH 4, 5, 6, and 7) or concentrations (0.67, 3.35, and 6.03%) of Zn compounds (Zn acetate and Zn sulfate). In general growth rates of S. typhimurium poultry isolate appeared to be more reduced by Zn acetate than by Zn sulfate and more reduced in minimal media compared to rich media.

Use of a Salmonella typhimurium hilA fusion strain to assess effects of environmental fresh water sources on virulence gene expression.

Many fruits and vegetables are irrigated with water from rivers, lakes and even wastewater systems. Irrigation may be a route for the introduction of Salmonella. Our objectives in this study were to determine survivability and virulence expression in a strain of Salmonella typhimurium when exposed to environmental water sources. Virulence expression was measured using a beta-galactosidase assay on a hilA:lacZY fusion strain of S. typhimurium. Water samples for environmental impact studies were taken from a local pond and specific sites along the Rio Grande River, which serves as a source of irrigation water in southern Texas. There was a significant difference (p<0.05) of virulence expression among the water sites. Certain regions along the Rio Grande River yielded greater amounts of beta-galactosidase activity than others. All sites yielded at least a two-fold greater virulence response than S. typhimurium grown in brain heart infusion. Salmonella survivors were enumerated as colony forming units (CFU)/ml as plated on a selective medium for the duration of 1 week and beta-galactosidase assays were performed to determine a possible correlation between culturable cells and virulence gene expression. Bacterial cells remained viable but decreased after 7 days incubation. In conclusion, water sampled at specific locations and at different times water samples exhibited differences in virulence expression in S. typhimurium.

Growth kinetics response of a Salmonella typhimurium poultry marker strain to fresh produce extracts.

The purpose of this research was to assess growth response of a Salmonella typhimurium poultry marker strain to fresh homogenized vegetables. Salmonella growth rates were significantly higher (p<0.05) in jalapeno extracts than any other produce extract examined. Growth rates on samples of broccoli and lettuce extracts were greater (p<0.05) than the respective growth rates on bell pepper and tomato. Broccoli extracts yielded the highest extent of growth (4 h optical density) followed by jalapeno and bell pepper extracts. From this study, it appears that fresh produce extracts have different abilities to significantly alter growth response in Salmonella. This could potentially be explained by the variations of pH, nutrient availability to the bacteria, or unknown components found within fresh produce.

Recovery of a marker strain of Salmonella typhimurium in litter and aerosols from isolation rooms containing infected chickens.

Screening of poultry flocks for foodborne pathogen Salmonella contamination is critical for Salmonella control in preharvest stages of poultry production. In this study, two sampling methods (litter and air filter) were compared for detection of S. typhimurium from experimentally infected chicks some of which had received either a probiotic competitive exclusion culture or transfer of cecal contents from salmonellae-free adult birds. At 4, 9, and 11 days after inoculation, S. typhimurium samples were enumerated by selective plating. For both types of sampling, the control birds yielded the greatest levels of environmental contamination followed by the samples from the probiotic inoculated birds with the birds receiving the cecal transfer culture having the lowest levels of contamination. Although the two sampling methods responded in a similar fashion, detection sensitivity needs to be increased for air filter sampling.