ENVIRONMENT AND HEALTH Effects of Hen Age, Bio-Mos, and Flavomycin on Poult Susceptibility to Oral Escherichia coli Challenge1

The effects of hen age, Escherichia coli, and dietary Bio-Mos and Flavomycin on poult performance from 1 to 21 d were studied. Day-of-hatch BUTA (BIG6) male poults were gavaged orally (1 mL) with approximately 108 cfu/mL E. coli composed of four serotypes or sterile carrier broth. A mixture of the same E. coli cultures was added to the poults’ water troughs to attain a concentration of approximately 106 cfu/mL on a weekly basis to ensure a continuous bacterial challenge. Within each E. coli split plot treatment group, poults from hens of different ages (33 and 58 wk of age) were fed diets containing Bio-Mos (1 g/kg feed), Flavomycin (2.2 mg active ingredient/kg feed), Bio-Mos plus Flavomycin, or a control diet, in a randomized complete block design. This experiment yielded eight treatments per challenge group. At Weeks 1 and 3, eight birds from each treatment from the E. coli challenged and unchallenged groups were (