Using varying levels of formic acid to limit growth of Salmonella gallinarum in contaminated broiler feed

Reported here are the effects of added formic acid on inhibitory effect of Salmonella gallinarum in poultry feed. Two experiments were conducted to investigate the viability of S. gallinarum and pH of poultry feed using different dietary formic acid levels (0.0, 0.5, 1.0 and 1.5%) on inhibitory effect of S. gallinarum in broiler feed. Experiment one was conducted to investigate the viability of S. gallinarum and pH of artificially contaminated diet at 0, 1, 3, 5 and 7 days after treatment in vitro. Formic acid showed a significant (p<0.05) reduction in the viability for all treatments with time after treatment. Various formic acid levels in vitro showed a reduction in the pH of the diet depending upon the concentration of treated acid, and the diet remained acidic below the growth range of S. gallinarum. This meant that the bacterial cells were exposed to stressful conditions that made them unable to grow. Experiment two was conducted to find out the effect of dietary formic acid levels on S. gallinarum colonization and pH in the contents of crop, small intestine, large intestine and ceca and mortality rate of broiler chicks at 7, 14 and 21 days of age when fed artificially contaminated diet with S. gallinarum. The numbers of S. gallinarum re-isolated from all treated groups except in groups treated with 0.5% formic acid, decreased significantly (p<0.05) compared with the control group. The treatment significantly (p<0.05) lowered the pH of the crop, small intestine, large intestine and ceca contents in all groups except the groups treated with 0.5% formic acid compared with the control. All treated groups showed a significant (p<0.05) reduction in overall mortality rate during the experimental period (3 to 21 days) compared with the control. The results indicate that addition of formic acid in a total concentration of 1.5% to the diet of newly hatched broiler chicks significantly decreases the contamination of diet with S. gallinarum.