Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 1999
Publication Date: N/A
Interpretive Summary: Feed withdrawal is a common practice employed by poultry producers. Feed withdrawal consists of denying the animals access to feed immediately before they are shipped to poultry processing plants. By reducing the amount of contents contained in the broilers' digestive system, feed withdrawal decreases the spread of feces between the animals during transport to the processing plant and during processing in the plant. Feed withdrawal has been linked to increases in the number of salmonellae bacteria found in the digestive tract of broiler chickens; however, and salmonellae bacteria from contaminated poultry have been associated with foodborne disease in humans. In this study changes in the crops of the digestive tract of broilers subjected to feed withdrawal were examined. Significant decreases in crop weights and acidity occurred during the early hours of feed withdrawal. The number of beneficial bacteria in the crop decreased throughout feed withdrawal, but the number of harmful bacteria remained the same. Findings indicate that feed withdrawal produces changes in the crop of broilers that create an environment more suitable for the survival and growth of potentially harmful bacteria, such as salmonellae.
Technical Abstract: Trials were conducted to determine the effect of feed withdrawal on the weight, pH, native bacterial flora, and Salmonella typhimurium colonization of the crops of market-age broilers. Broilers were provided medicated or unmedicated feed and then subjected to feed withdrawal for 0 to 24 h in transportation crates or on litter. After feed withdrawal, broilers were stunned, bled, scalded, and picked. Crops were aseptically removed and weighed. The crops were then blended in 20 mL of distilled water, and the pH values of the blended suspensions were measured. The numbers of aerobic bacteria, Enterobacteriaceae, S. typhimurium, and lactic acid bacteria in the suspension were enumerated on appropriate bacteriological media. Feed withdrawal produced significant decreases in the crop weights. Crop pH increased by 1.0 unit within 6 h of feed withdrawal. The number of Enterobacteriaceae and S. typhimurium recovered from the crop generally decreased during the first 12 h of feed withdrawal, then remained unchanged or increased during the final 12 h of the 24 h feed withdrawal period. The number of lactic acid bacteria recovered from the crop usually decreased as the duration of feed withdrawal increased, however. Trends in changes in crop weights, pH, native microflora, or colonization by S. typhimurium were similar in broilers subjected to feed withdrawal on litter or in crates and in broilers provided medicated or unmedicated feed before initiating feed withdrawal. Findings indicate that a decrease in the number of lactic acid producing bacteria in the crop and an increase in crop pH may be related to reducing the ability of the crop to resist colonization by Enterobacteriaceae during extended feed withdrawal.