Relative contribution of cattle to contamination of pasture with Nematodirus battus under an alternate grazing system of husbandry.

Calves, aged six months grazing on pasture on which lambs infected with Nematodirus battus had grazed the previous season, became infected and passed eggs of N battus. Transfer of these calves onto 'clean' pasture showed that their faecal contamination was sufficient to cause moderate infections of N battus in lambs grazing this area the following season. It was also shown that significant N battus contamination could survive on pasture for at least 18 to 24 months in the absence of further grazing by sheep. Under husbandry systems involving alternate grazing there is likely to be a combination of contamination by young susceptible calves, and a two year carry-over of infectivity.