Effect of Dietary Formic and Propionic Acids Mixture on Limiting Salmonella pullorum in Layer Chicks

This investigation was conducted to study the effect of dietary formic acid (FA) and propionic acid (PA) mixture on inhibitory effect of Salmonella pullorum in layer chicks. Nine groups of one day-old layer chicks in addition to positive and negative controls, were fed with acids treated feed containing mixture of different acids concentrations, from 0.5% and 0.5% up to 1.5% and 1.5% FA and PA, respectively. Positive and negative controls were fed untreated feed. Groups except the negative control were challenged orally on day three with $10^4$ cfu/ml S. pullorum. Cloacal swabs were taken at three successive days and at 7, 14 and 21 days of challenge. After 1, 2 and 3 weeks after challenge, 4 chicks from each group were sacrificed and crop and cecal contents were examined for S. pullorum and pH. The numbers of S. pullorum positive culture from the excretion of all treated groups except groups treated with mixture of 0.5% and 0.5%, 1% and 0.5%, 0.5% and 1% FA and PA decreased significantly (p<0.05) as compared with the positive control. The mortality rates of all treated groups except the group treated with 0.5% FA and 0.5% PA were decreased significantly (p<0.05) as compared with the positive control. The treatment significantly (p<0.05) lowered the pH of the crop and cecal contents in all groups except the group treated with 0.5% FA and 0.5% PA as compared with the control. Also, the treatment significantly (p<0.05) lowered the pH of the crop and cecal contents in all groups after three weeks of treatment compared to the first and second weeks. The treatments significantly (p<0.05) lowered the frequency of S. pullorum recovery from crop and cecal contents in six groups treated with 1.5 and 0.5, 1 and 1, 1.5 and 1, 0.5 and 1.5, 1 and 1.5, 1.5% and 1.5% FA and PA respectively. These results indicate that addition of FA and PA mixture in a total concentration of 2 % or more to the diet of newly hatched infected layer chicks significantly decreases the crop and cecal colonization by S. pullorum and significantly decreases S. pullorum fecal excretion and reduced the chick mortality rate.