The intestinal microbiota, epithelium, and immune system provide resistance to enteric pathogens. Recent data suggest that resistance is not solely due to the sum of the components, but that cross-talk between these components is also involved in modulating this resistance. Inhibition of pathogens by the intestinal microbiota has been called bacterial antagonism, bacterial interference, barrier effect, colonization resistance, and competitive exclusion. Mechanisms by which the indigenous intestinal bacteria inhibit pathogens include competition for colonization sites, competition for nutrients, production of toxic compounds, or stimulation of the immune system. These mechanisms are not mutually exclusive, and inhibition may comprise one, several, or all of these mechanisms. Consumption of fermented foods has been associated with improved health, and lactic acid bacteria (lactobacilli and bifidobacteria) have been implicated as the causative agents for this improved health. Research over the last century has shown that lactic acid bacteria and certain other microorganisms can increase resistance to disease and that lactic acid bacteria can be enriched in the intestinal tract by feeding specific carbohydrates. Increased bacterial resistance to antibiotics in humans has caused an increase in public and governmental interest in eliminating sub-therapeutic use of antibiotics in livestock. An alternative approach to sub-therapeutic antibiotics in livestock is the use of probiotic microorganisms, prebiotic substrates that enrich certain bacterial populations, or synbiotic combinations of prebiotics and probiotics. Research is focused on identifying beneficial bacterial strains and substrates along with the conditions under which they are effective.

In modern poultry production systems, environmental stressors may influence bird performance and susceptibility to pathogens such as Salmonella Enteritidis. Experiments were conducted to determine the influence of 24-h feed withdrawal and 24-h exposure to high temperature (30 degrees C) on intestinal characteristics of broilers. Attachment of Salmonella Enteritidis to ileal tissue was determined using an in vitro ileal loop assay. Changes in commensal intestinal microbial populations were determined using denaturing gradient gel electrophoresis, and alterations in ileal morphology were determined histologically. Ex vivo attachment of Salmonella Enteritidis to ileal tissues increased by 1.5 logs (9.05 log10 vs. 7.59 log (10) Salmonella Enteritidis/g of ileal tissue; P = 0.0006) in broilers fasted for 24 h. Similarly, ileal tissues from birds subjected to 30 degrees C for 24 h had increased ex vivo attachment of Salmonella Enteritidis (8.77 log(10) vs. 8.50 log(10) Salmonella Enteritidis/g of ileum; P = 0.01) compared with birds held at 23 degrees C. Exposure to 30 degrees C for 24 h also altered microbial community structure in the ileum and cecum. Subjecting birds to 30 degrees C for 24 h reduced crypt depth (6.0 vs. 7.8 microm, respectively; P = 0.002), but had no effect on villus height or villus:crypt ratio. This research shows that acute stressors in poultry production systems can cause changes in the normal intestinal microbiota and epithelial structure, which may lead to increased attachment of Salmonella Enteritidis.

Studies were conducted to determine the effect of galactan on the colonization of E. coli and lactobacilli and ileal pH and volatile fatty acid production in the digestive tract of the weanling pig. In each of two replicate trials, eight 21-d-old nursing pigs were cannulated in the terminal ileum. After a 7-d recovery period, the pigs were weaned and randomly assigned to two test diets: 1) a corn-soybean meal-based control diet and 2) a similar diet containing 1% galactan. On d 1 after weaning, all pigs were orally subjected to K88+ E. coli (2 x 10(9) colony forming units). Ileal digesta samples were collected on d 0, 2, 4, 6, 8, and 10 after weaning and assayed for total E. coli, K88+ E. coli, lactobacilli, pH, and VFA. At the end of the trials, the pigs were killed and digesta samples were collected from the stomach, duodenum, cecum, and colon. Assays similar to those performed on the digesta samples collected from ileal cannulas were performed. Pigs fed 1% galactan had lower (P < .10) ileal pH, lower (P < .05) total E. coli on d 6 and 8, and lower (P < .05) K88+ E. coli concentrations in the ileum than pigs fed the control diet. There were no differences in ADG or gain:feed ratio between diets. The VFA concentrations were not different in the ileum between diets. The VFA were higher (P < .10) on d 0 than on any other day of the study. Acetate and isobutyrate concentrations were lower (P < .10) in the cecum in pigs fed 1% galactan.(ABSTRACT TRUNCATED AT 250 WORDS)

Rates of degradation of DL-methionine and a number of methionine derivatives by rumen microorganisms were studied in vitro. Methionine hydroxy analog, the ammonium salt, and the amide derivative of methionine hydroxy analog were degraded more slowly than was methionine. Methyl and ethyl esters of methionine hydroxy analog were rapidly converted to methionine hydroxy analog, which was then degraded. Whole rumen contents were separated into protozoal and bacterial fractions, and rates of disappearance of [14C]carboxyl-labeled methionine and methionine hydroxy analog were determined. Disappearance of the label tended to be slower in the bacterial fraction; however, incorporation into cellular material tended to be higher for the bacterial than for the protozoal fraction. Disappearance of labeled methionine hydroxy analog was slower than labeled methionine in all fractions. Addition of unlabeled methionine inhibited disappearance of labeled methionine hydroxy analog, but unlabeled methionine hydroxy analog did not affect disappearance of labeled methionine. The effect of either Na2SO4, methionine, or methionine hydroxy analog on neutral detergent fiber digestion was related to amount of sulfur in the medium and not source of sulfur.

Thermographic imaging is a noninvasive diagnostic tool used to document the inflammatory process in many species and may be useful in the detection of subclinical bumblefoot and other inflammatory diseases. Bumblefoot is a chronic inflammation of the plantar metatarsal or digital pads of the foot (pododermatitis), or both. It is one of the major health problems in birds including chickens and is responsible for significant economic losses in commercial poultry operations. Early diagnosis of bumblefoot is essential for the prevention of economical loss and the improvement of animal well-being. The object of this study was to determine the suitability of thermography for the identification of subclinical bumblefoot in chickens. Experiment 1 was designed to validate thermography as a tool for screening avian populations for bumblefoot. The plantar surface of the feet of 150 randomly selected hens was imaged using a thermal camera. The thermal images were identified as suspect, positive, or negative for bumblefoot based on thermal patterns of the plantar surface. Visual inspection of the feet identified as suspect followed 14 d later. A visual score of clinical, mildly clinical, or negative for bumblefoot was assigned, based on gross pathological changes in the plantar surface. A correlation between initial thermal images identified as suspect for bumblefoot and a visual score of positive 14 d later was 83% (P < 0.01). In experiment 2, hens whose feet were free of lesions were inoculated in the metatarsal foot pad with Staphylococcus aureus. Thermal images and visual clinical scores were taken, prechallenge and 1, 2, 3, 4, and 7 d postchallenge. The correlation between thermal images classified as clinical and a visual score of clinical for bumblefoot was 86.7% (P < 0.001). However, the correlation between the thermal images classified as mild (subclinical) and a visual score of mild was only 26.7%, suggesting that thermography is a more sensitive indicator of subclinical infection than visual appraisal. Thermography may thus provide a useful tool for screening avian populations for signs of bumblefoot, early in the course of the disease, which will improve recovery percentages and bird well-being.