Effect of diet-induced low-grade, chronic inflammation on susceptibility of broilers to Salmonella colonization and pathogenicity.

Removal of growth-promoting antibiotics (AGPs) is associated with the emergence of chronic, low-level gut inflammation induced by environmental stressors, especially diet components. However, there have been no reports demonstrating an increased susceptibility of birds to pathogenic bacteria such as Salmonella following the removal of AGPs from the animal feed. For the present studies, we hypothesize that a dietary-derived, low-grade chronic intestinal inflammation increases the susceptibility of young broiler chickens to intestinal colonization, extraintestinal infection, and the pathogenicity of Salmonella enterica serovar Enteritidis (SE). Two separate experiments were conducted separating a total of 250 birds/experiment into 2 feeding regimes: a normal basal corn-soy diet and a corn-soy + 30 % rice bran starting on the day of hatch through 28 days. Each diet contained 25 non-challenged control birds with the remaining 100 birds/diet divided into groups of 25 that were orally challenged with SE at either 1-, 7-, 14-, or 21-days post-hatch. At 28 days post-hatch, all birds were euthanized to evaluate SE intestinal colonization and organ invasion, and all birds and left-over feed were weighed to evaluate weight gain, feed intake, and feed conversion. The high NSP diet had a detrimental effect on the animals' performance as evidenced by significant reduction in weight gain and feed intake and increased feed conversion. Birds fed the high NSP diet for at least 7 days were found to have significantly more detectable SE in both the ceca and in the liver compared to the control corn-soy fed birds. Lastly, there was a significant increase in SE recovery in birds fed the high NSP diet for at least 7 days. These results provide evidence that the diet-induced chronic gut inflammation created a more advantageous colonization environment for Salmonella. The consequence of low-grade chronic intestinal inflammation remains a major issue within the poultry industry as it is felt economically since it affects FCR and renders birds more susceptible to enteric pathogen colonization and invasion.