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* Corresponding author: Tel: (64-3) 325 3803; Fax: (64-3) 325 3851; e-mail: stankiem@lincoln.ac.nz
As immunisation of young lambs against parasitic nematodes is not currently feasible, we were interested to know whether drug treatment or immunisation of pregnant ewes on pasture with drug-abbreviated infections during pregnancy would have practical implications on the periparturient rise in excretion of parasite eggs by ewes and live-weight gain in lambs born to these ewes. Romney 4-year-old ewes were immunised with three (group 1), two (group 2) and one (group 3) immunising doses of Ostertagia circumcincta together with Trichostrongylus colubriformis. Group 4 sheep were treated with oxfendazole only. Group 5 sheep served as an untreated controls and non-lactating sheep (group 6) were used as additional controls. These results show that periparturient rise in parasite eggs was in the 4-year-old ewes moderate, but significantly decreased either by drug treatment or by drug-abbreviated immunisation. There was a tendency for lambs born from immunised ewes to gain weight more rapidly than lambs born from non-immunised ewes.