Poster Presentations ASAS/ADSA Food Safety and PSA Pathology

E. coli 0157:H7 is an emerging food-borne pathogen implicated in several outbreaks. Fecal shedding of the pathogen constitutes the mode of entry into the human food chain. We compared the influence of dietary acid-detergent fiber (ADF) concentration on fecal shedding of the pathogen and meat production efficiency of lambs. Fourteen growingfinishing Suffolk ram lambs averaging 28 1.3 kg in body weight were arranged in two 7 x 7 Latin squares with 1week adaptation and 2-weeks of fecal sample collection and fed diets with 5, 10, 15, 20, 25, or 35 % ADF content, ranging from all-concentrate (5 % ADF) to all-forage diet (35 % ADF). Diets were fed daily at the rate of 1.4 kg/head. Fecal samples were collected weekly and analyzed for E. coli O157:H7 using modified tryptic soy broth with novobiocin as a pre-enrichment broth and cefixim-tellurite sorbitol MacConkey agar (CT-SMAC) as a selective media. E. coli O157:H7 was confirmed by its reaction with O157 and H7 antisera. Lamb growth rate and daily dry matter intake were determined and composite feed samples analyzed for nutrient content. When fed 10, 15, 20, 25, 30 and 35 % ADF in the diet, E. coli 0157:H7 shedding was comparable among treatments suggesting that within 10 to 35 % ADF range dietary fiber does not impact E. coli O157:H7 shedding. However, lamb growth rate and feed efficiency were significantly lower (P < 0.05) for the 25, 30 and 35 % ADF diets. The 5 % ADF (100 % concentrate) diet resulted in significantly higher (P < 0.05) shedding of the pathogen (6.09 versus 5.12, 4.82, 5.21, 5.05 and 5.04 log 10 CFU/g of feces for the 10, 15, 20, 25, 30, and 35 % ADF diets, respectively) than the other treatments. The results suggests that increasing the ADF content of the concentrate ration between 10 and 20 % ADF results in significant reduction in the shedding of E. coli O157:H7 as compared to 5, 25, 30, and 35 % ADF diets without adversely affecting animal meat production efficiency.