Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/10/2007
Publication Date: 6/1/2007
Citation: Berrang, M.E., Ladely, S.R., Meinersmann, R.J., Cray, P.J. 2007. Sub-therapeutic Tylosin Phosphate in Broiler Feed Affects Campylobacter on Carcasses During Processing. Poultry Science. 86(6):1229-1233. Interpretive Summary: Broilers can be fed low doses of antibiotic drugs to improve the rate of growth. Bacteria present in the chicken gut can become resistant to antibiotic drugs when those drugs are used in low doses in animal feed. Human pathogens that are drug resistant can cause disease which is difficult to treat with antibiotic drugs. Tylsoin is a drug approved for use in broiler feed. Erythromycin, the most common drug used to treat human campylobacteriosis, is in the same class of drugs as tylosin. It is unclear how low dose feeding of tylosin would affect Campylobacter on chicken carcasses during slaughter and processing. Campylobacter positive broiler chicks were fed low levels of tylosin or unmedicated feed for the last 4 weeks of grow-out. Broilers were processed under conditions which very closely simulate commercial processing. Carcasses were examined at three stages: early, mid and late processing. Broilers that were fed tylosin produced carcasses with the same numbers of Campylobacter early and mid processing as those that were not fed tylosin. At late processing, the oven ready carcass from a tylosin fed flock had lower numbers of Campylobacter than did those from the unmedicated flock. However, all Campylobacter detected on carcasses from the medicated broilers were resistant to tylosin and erythromycin.
Technical Abstract: Tylosin is an antimicrobial drug approved for use in broiler feed at sub-therapeutic levels for purposes of growth promotion. Erythromycin is often the drug of choice for treating humans with campylobacteriosis. Both tylosin and erythromycin are classified as macrolide drugs and cross resistance between these antimicrobials occurs. Commercial broiler chicks were placed in isolation grow-out chambers and colonized with Campylobacter jejuni. At 14 days of age broilers began to receive a diet including 20 g tylosin phosphate per ton which was continued ad libitim for the rest of grow-out. Control broilers received the same diet without tylosin. At 42 days of age, broilers were processed in a pilot plant with equipment which closely modeled commercial conditions. Carcass rinses were collected after feather removal, after inside/outside washing and after immersion chilling. Campylobacter numbers after feather removal were not different according to feed type (3.53 log cfu per ml rinse for control carcasses and 3.60 for those fed medicated feed). Likewise, medicated feed did not affect Campylobacter numbers on carcasses after inside/outside washing (3.11 and 3.07 log cfu per ml rinse). However, carcasses of broilers fed medicated feed had lower numbers of Campylobacter after chilling (1.45 log cfu/ml rinse) compared to control carcasses (2.31 log cfu/ml rinse). No Campylobacter isolated from control carcasses were resistant to erythromycin but all Campylobacter recovered from carcasses fed tylosin were resistant to erythromycin. Application of tylosin in feed results in lower Campylobacter numbers on chilled carcasses; however, the Campylobacter that do remain are resistant to erythromycin.