Populations of digestive microflora in chickens change with age and are affected by diet, stressors, and performance enhancers. Culturing techniques used to profile a bacterial community inadvertently select for some organisms while excluding others. Several molecular-based techniques have been used to profile mixed microbial populations on the basis of DNA extracted from the entire community. Denaturing gradient gel electrophoresis was used in the present study to examine PCR-amplified fragments (amplicons) of a 16S ribosomal DNA variable region from predominant digestive bacteria. The objective of the study was to examine changes in digestive microbial communities of developing Leghorn chicks and molted Leghorn hens. Dendrograms of amplicon patterns indicated approximately 51% similarity between cecal bacteria composition in Leghorn chicks less than 20 d old and chicks greater than 20 d old. Cecal communities in Leghorn chicks given a competitive exclusion culture exhibited 21% correlation at all ages with those in control chicks. Nonmolted and molted hens had 40% similarity between cecal communities, whereas diets with low calcium (0.8% wt/wt) and excess zinc (2,800 mg/kg) lessened population differences (90% similarity). Results indicated the potential usefulness of the molecular-based denaturing gradient gel electrophoresis to monitor changes in digestive bacterial communities in chickens.

High fiber and nonstarch polysaccharide-based poultry diets have received more interest recently for retaining or promoting beneficial gastrointestinal microbial populations. The objective of this study was to investigate and compare the in vitro potential fermentability of high-fiber feed substrates (HFFS) by laying hen cecal microflora. Feed sources examined included soybean meal, soybean hull, beet pulp, wheat middlings, ground sorghum, cottonseed meal, 100% alfalfa meal, 90% alfalfa + 10% commercial layer ration, 80% alfalfa + 20% commercial layer ration, and 70% alfalfa + 30% commercial layer ration. Cecal contents and HFFS were incubated anaerobically in serum tubes at 39 degrees C for 24 h. Samples from 2 trials were analyzed at 0 and 24 h for short-chain fatty acids (SCFA). Short-chain fatty acids in samples at 0 h were subtracted from 24-h samples to determine the net production of SCFA. In both trials involving HFFS incubations with cecal inocula, acetate production was highest followed by propionate and butyrate whereas isobutyrate and isovalerate production were in trace amounts. In trial 2, detectable valerate production appeared to consistently occur with alfalfa-based HFFS. It was clear that SCFA production was largely dependent upon HFFS, because cecal inoculum alone yielded little or no detectable SCFA production. For HFFS incubations without cecal inocula, acetate production was highest; propionate and butyrate were similar, and isobutyrate, valerate, and isovalerate production were in trace amounts. Polymerase chain reaction-based denaturing gradient gel electrophoresis results from both trials indicated 69 and 71% similarity for comparison of all feed mixtures in trials 1 and 2, respectively. All alfalfa-based HFFS yielded a higher similarity coefficient in trial 2 than in trial 1 with a band pattern of 90% similarity; diets containing 90% alfalfa + 10% commercial layer ration and 80% alfalfa + 20% commercial layer ration in trial 2 formed a subgroup with a 94% microbial similarity coefficient. These data suggest that high fiber sources may contribute to the fermentation and microbial diversity that occurs in the ceca of laying hens.

Foodborne disease caused by Salmonella is of public health and economic significance. In order to assess the practical effectiveness of a new intervention strategy, experimental chlorate preparations (ECP) were administered via the drinking water to weaned and finished pigs that had been orally challenged the previous day with 10(9)-10(10) colony-forming units of Salmonella serovar Typhimurium. After 24 or 36 h ad libitum access to 0X, 1X or 2X ECP treatment (where X is the concentration estimated to deliver a minimal daily effective dose), the pigs were euthanized and gut contents and lymph tissue collected at necropsy were cultured for the challenge Salmonella. Drinking water administration of ECP effectively reduced (p < 0.05) caecal Salmonella concentrations and, with the weaned pigs, tended (p < or = 0.10) to reduce rectal Salmonella concentrations. No negative effects of ECP treatment on water intake and animal wellbeing were observed and only marginal effects on gut fermentation characteristics occurred. The bactericidal effect of administering ECP in drinking water was relatively rapid, with reductions in caecal Salmonella concentrations occurring within 24 h. These results suggest that ECP administered to pigs just days before slaughter may reduce gut concentrations of Salmonella; however, the impacts of such reductions on slaughter hygiene have yet to be determined.

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Continuous-flow (CF) chemostate cultures were used as models to determine the potential usefulness of undefined porcine cecal bacteria as competitive exclusion (CE) cultures against colonization by Salmonella Typhimurium. One culture, pCF1, was derived from cecal bacteria of an animal maintained on antibiotic-free feed, while the other culture, pCF4, was derived from cecal bacteria of an animal maintained on feed containing chlortetracycline. The effectiveness against a chlortetracycline-resistant Salmonella Typhimurium was examined in CF cultures maintained in the absence (pCF1 and pCF4) and presence (cpCFl and cpCF4) of chlortetracycline. CF cultures were inoculated with each of 10(2), 10(4), and 10(6) Salmonella Typhimurium CFU/ml. Chemostat inocula of 10(2) Salmonella CFU/ml resulted in no Salmonella Typhimurium being detected at 2 and 3 days postinoculation in pCF1 and pCF4, respectively, and after 2 days in both cpCF1 and cpCF4. Inoculations of 10(4) Salmonella Typhimurium CFU/ml resulted in clearance from pCF1 and pCF4 within 4 days and within 3 days from cpCF1 and cpCF4. Following inoculation with 10(6) CFU/ml, no Salmonella Typhimurium were detected in all CF cultures by 6 days postinoculation. The results indicated that in vitro CF cultures of porcine cecal bacteria were able to inhibit the growth of Salmonella Typhimurium. The ability to limit Salmonella Typhimurium growth was not restricted by prior exposure of the cecal bacteria to the feed additive chlortetracycline. The present study demonstrates the potential application of CF cultures as models to aid in the identification of CE cultures against salmonellosis in pigs.