Physical, chemical, and microbiological changes in the crop of broiler chickens subjected to incremental feed withdrawal

Trials were conducted to determine the effect of feed withdrawal on the wei ght, pH, native bacterial flora, and Salmonella typhimurium persistence in crops of broilers. Six-week-old broilers were provided medicated or unmedic ated feed and were subjected to feed withdrawal for 0 to 24 h in transporta tion crates or on litter. After feed withdrawal, broilers were stunned, ble d, scalded, and picked. Crops were aseptically removed and weighed. Crops w ere then blended in 20 mL distilled water, and pH values of the suspensions were measured. Aerobic bacteria, Enterobacteriaceae, S. typhimurium, and l actic acid bacteria in the suspension were enumerated on appropriate bacter iological. media. Feed withdrawal produced significant decreases in the cro p weights. Crop pH increased by 1.0 unit within 6 h of feed withdrawal. Ent erobacteriaceae and S. typhimurium populations generally decreased during t he first 12 h of feed withdrawal and remained unchanged or increased during the final 12 h of the 24-h feed withdrawal period. The number of lactic ac id bacteria recovered from the crop usually decreased as the duration of fe ed withdrawal increased. Changes in crop weights, pH, native microflora, or the recovery of S. typhimurium from the crop were similar in broilers subj ected to feed withdrawal on litter or in crates and in broilers provided me dicated or unmedicated feed before initiating feed withdrawal. Findings ind icate that a decrease in the number of lactic acid producing bacteria in th e crop and an Increase in crop pH may be related to the reduction of anti-E nterobacteriaceae activity in the crop during extended feed withdrawal.