Response of mibolerone-treated chickens to infectious bursal disease virus.

The response of mibolerone-treated chickens to infectious bursal disease virus (IBDV) was studied. Chickens fed a ration containing mibolerone at 1.5 parts per million (ppm) developed bursal atrophy by 4 weeks of age. No indication was found that mibolerone prevented IBDV infection even after 7 weeks of feeding. Furthermore, only chickens treated with mibolerone died when infected with IBDV at 2 or 3 weeks of age, and treated chickens had more severe clinical signs than did untreated controls when infected at 4-8 weeks of age. Chickens fed mibolerone had lower body weights than unmedicated controls, and apparently had a lower antibody response to IBDV and to bovine serum albumin.