Use of an ivermectin bolus against gastrointestinal nematode and lungworm infections in first-year grazing calves.

Two groups of first-year grazing cattle each were either left untreated as controls (group 1) or treated with an ivermectin bolus at turnout (group 2). Whereas group 1 suffered from dictyocaulosis, the bolus treated calves remained healthy. Shedding of lungworm larvae was completed prevented and gastrointestinal nematode egg output effectively reduced. During the 154 day grazing season the ivermectin bolus provided a season-long protection against parasitic gastroenteritis and bronchitis.