Effects of tannic acid on cecal volatile fatty acids and susceptibility toSalmonella typhimurium colonization in broiler chicks

Young chickens are more susceptible to Salmonella colonization than older c hickens that have developed resistance with age as native microftora become established. Elevated concentrations of cecal propionic acid and total vol atile fatty acids (VFA) have been observed by many researchers to be indica tors of establishment of anaerobic microflora and protection against Salmon ella colonization of the ceca. Disruption of the native microflora or compe titive exclusion (CE) cultures by components of diets, such as tannic acid (TA), could alter the concentrations of propionic acid and total VFA and po ssibly affect Salmonella colonization. Two experiments were conducted using day-of-hatch, mixed-sex broiler chicks to evaluate the effects of TA on ce cal VFA and the susceptibility to Salmonella colonization. All chicks in bo th experiments were challenged orally with 10(4) cfu of Salmonella typhimur ium (ST) on Day 3 (Experiment 1) or Day 4 (Experiment 2). One-half of the c hicks were orally gavaged on the day of hatch with a CE culture (PREEMPT(TM )) and were fed diets containing 0, 0.75, or 1.5% TA for up to 12 d of age. Chicks were maintained in batteries in separate rooms for the experimental period. There were some alterations in concentrations of cecal propionic a cid or total VFA in chicks fed diets containing 0.75 or 1.5% TA in non CE-t reated chicks and in CE-treated chicks. No significant differences were obs erved for numbers of Salmonella cecal culture-positive chicks or in the num bers of ST in the cecal contents due to dietary content of TA. With minor e xceptions, the chicks treated with the CE culture had higher cecal concentr ations of propionic acid and were less susceptible to Salmonella colonizati on than the non CE-treated chicks. Further research is necessary to determi ne the biological significance of these changes.