Supplemental use of liquid amprolium in skip-a-day feeding of replacement pullets

The addition of liquid amprolium to the drinking water on days when medicated (amprolium) ration was not fed in a restricted feeding (skip-a-day) program improved protection against a primary exposure to Eimeria acervulina and Eimeria tenella, yet still allowed for the development of protective immunity to subsequent challenge. With E. tenella, the best protection, as measured by reduction of lesion score, was provided by amprolium given in the drinking water on alternate days to feed medication when compared with the use of amprolium only in the feed or liquid amprolium at less frequent intervals (every second or third nonfeeding day). With Eimeria maxima, amprolium in the feed did not significantly lower lesion score compared with the score in unmedicated pullets; however, the further addition of amprolium to the drinking water did. When pullets were reared in floor pens previously seeded with coccidia, amprolium medication in the feed alone reduced the E. tenella-induced mortality rate from 28 to 8%. The addition of amprolium in the drinking water on nonfeeding days eliminated all deaths. Floor-reared pullets were caged after 3 wk and challenged 1 wk later with the same species of coccidial oocysts used to immunize on the floor. Coccidial lesion scores following challenge were eliminated or markedly lower than in pen-reared (unimmunized) pullets similarly challenged. This indicated that protective immunity developed despite the use of amprolium in the drinking water.