The effect of feeding diets containing avoparcin and monensin on the occurrence of Salmonella in caecum and liver in experimentally infected chickens.

In two experiments (Experiments A and B) chickens experimentally infected with S. infantis at 7 days of age and fed diets containing both avoparcin (10 ppm) and monensin (90 ppm) showed a higher frequency of Salmonella-positive livers and higher caecal counts of Salmonella 1 and 2 weeks after challenge than similarly infected chickens fed only avoparcin (10 ppm). The results may indicate a synergistic action between the two drugs on the ability of chickens to withstand Salmonella infections.