Three groups of four calves were raised parasite-free. Each group received a different diet. At the moment of infection one group was fed with milk equivalent artificially dried grass, and concentrates, the second with water, grass pellets (16 mm), and concentrates, while the third was fed with water, artificially dried grass, and concentrates. Each animal was infected at an age of 8 weeks with 10,000 larvae of Ostertagia ostertagi and necropsied 28 days later, No significant differences between the groups were observed with regard to the number of worms post-mortem, length of worms, number of eggs per female, or gain of weight of the calves.