Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2002
Publication Date: 1/1/2003
Citation: COX JR, N.A., CRAVEN, S.E., MUSGROVE, M.T., BERRANG, M.E., STERN, N.J. EFFECT OF SUB-THERAPEUTIC LEVELS OF ANTIMICROBIALS IN FEED ON THE INTESTINAL CARRIAGE OF CAMPYLOBACTER AND SALMONELLA IN TURKEYS. JOURNAL OF APPLIED POULTRY RESEARCH. 2003. 12:32-36
Interpretive Summary: Since the 1950s, antimicrobials have been added to poultry feed at sub-therapeutic levels to minimize illness and promote growth. Despite the benefits to agricultural industry and domestic animals, there are fierce debates world-wide on whether or not this practice carries a consequence in terms of human health. Turkeys and broilers provided these additives are known to have increased weight gain, muscle yield, and feed conversion in part due to decreases in diseases such as coccidiosis and necrotic enteritis. Benefits achieved by adding these compounds to animals feeds are attributed in part to a shift in the gut microflora. However, studies have been published in which it was determined that competitive exclusion cultures, administered to birds to control colonization by human pathogens such as Salmonella, can be negatively affected by antimicrobials commonly used in poultry rations. Other published studies have reported an increase in Salmonella levels when experimentally challenged birds were fed diets containing low levels of antimicrobials. This study demonstrated that while naturally occurring populations of Campylobacter were virtually unaffected by antimicrobial feed additives, Salmonella populations were significantly decreased when commercial turkeys were fed rations containing flavomycin, virginiamycin, or monensin.
Technical Abstract: Antibiotics are often added to poultry feed to promote growth. This study was undertaken to examine how this may affect carriage of human pathogens in the ceca of turkeys. Female turkeys (150) five wk old, raised in commercial facilities being fed monsensin were transported to five isolation floor pens. All birds were maintained on the same basal diet containing monensin until 8 wk of age. At that time the diets fo the birds were adjusted as follows: a) no additive (no monensin), b) continued monensin @ 72 g/ton, c) virginiamycin @ 20 g/ton, d) flavomycin @ 2 g/ton, e) bacitracin @ 50 g/ton. Five birds from each group were sacrificed and the ceca were cultured on each of the following days: 1 d before addition of antibiotics and at 1 d, 3 d, 7 d and 16 d after addition of antibiotics to the feed. Ceca were aseptically removed, diluted 1:4 by weight with modified Cary-Blair medium and blended. Using direct plating,pre-enrichment and selective enrichment the samples were analyzed for Campylobacter and Salmonella. Characteristic colonies were confirmed with serological tests. Prevalence of Campylobacter positive birds were 88, 72, 88, 88, and 96% for treatments a - e, respectively. Salmonella cecal prevalence was 52, 12, 20, 8, and 52 % for the same treatments. A significant effect was noted only for treatments b, c, and d, and only for Salmonella cecal prevalence compared to treatment a.