The efficacy of strategic treatments with ivermectin pour-on against trichostrongylid and lungworm infections in first year grazing calves in northern Germany.

Three groups of 8 first year grazing calves each were either left untreated as controls (group 1), or were treated with 10 mg levamisole spot-on/kg bodyweight (group 2) or with 0.5 mg ivermectin pour-on/kg bodyweight 3, 8, and 13 weeks after turnout (group 3), respectively. Egg counts, herbage larval counts, worm counts of tracer calves, pepsinogen concentrations and weight gains showed a high efficacy of the strategic treatment in group 3 against gastrointestinal nematodes. The calves of group 1 and 2 developed clinical signs of parasitic bronchitis whereas the group 3 animals remained clinically healthy. The strategic treatment with ivermectin cleaned the respective pasture from infective lungworm larvae.