Efficacy of early season anthelmintic treatment against gastrointestinal nematodes

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Abstract
The efficacy of levamisole and ivermectin in multiple‐dose regimes for the control of parasitic gastroenteritis in first‐season grazing calves was evaluated on a dairy cattle farm in Belgium. Thirtynine female Holstein crossbred calves were randomly divided into three groups. Paddock I was used for the controls, paddock 2 for the levamisole group (dosed at 3, 6 and 9 weeks after the start of grazing) and paddock 3 for the ivermectin group (dosed at 3 and 8 weeks after turn‐out). The treatments were evaluated on the basis of live weight, faecal egg output, and serum pepsinogen levels. The impact of the therapeutic dosing at timed intervals during the first months of the grazing season was remarkable; egg output in the levamisole and ivermectin groups between June and early October was substantially lower. The treatments seem to adequately control Ostertagia, because serum pepsinogen values were much lower from August onwards. Better weight gains were observed in both the treatment groups. The experiment also illustrated the advantage of early housing of calves.