Efficacy, pharmacokinetics and effects on egg-laying and hatchability of two dose rates of in-feed fenbendazole for the treatment of Capillaria species infections in chickens

Laying broiler breeder hens infected with Capillaria obsignata were treated with in-feed fenbendazole either at a dose of 30 ppm for six days or 80 ppm for three days. The respective efficacies of treatment were 92.3 and 99.3 per cent. These results were a reflection of the plasma pharmacokinetics of fenbendazole and its metabolites in the regimens, which showed that the detectable plasma concentrations of the anthelmintically active fenbendazole sulphoxide in the second treatment were significantly greater than the first, with the area under the curve 1.34 times that of treatment 1. Both treatments produced a slight decline in egg production, but only the loss in production with treatment 1 was significant. Hatchability of eggs with both treatments was not significantly affected.