Assessment of criteria for improvement in Theileria orientalis sergenti infection tolerance

We examined the relationships between calf productivity, anemia and Theileria orientalis sergenti infection from records of 109 Japanese shorthorn calves during a grazing period and we quantified the relative importance of the T. orientalis sergenti infection-resistance criteria used. A decrease in average parasitemia (AvePara) and an increase in average packed cell volume (AvePCV) would cause a decrease in the number of drug treatments. An increase in AvePCV would decrease the number of drug treatments more efficiently than a decrease in AvePara. An increase in AvePCV would cause an increase in dairy gain, while a decrease in AvePara would cause a decrease in dairy gain. Therefore, an improvement in the capacity to control anemia development would improve T. orientalis sergenti infection resistance more efficiently than an improvement in the capacity to control parasitemia development.