The effect of anthelmintic treatment or immunisation of ewes during pregnancy on the periparturient rise in nematode parasite eggs excreted by ewes and on live-weight gain of lambs

As immunisation of young lambs against parasitic nematodes is not currently feasible, we were interested to know whether drug treatment or immunisatio n of pregnant ewes on pasture with drug-abbreviated infections during pregn ancy would have practical implications on the periparturient rise in excret ion of parasite eggs by ewes and live-weight gain in lambs born to these ew es. Romney 4-year-old ewes were immunised with three (group 1), two (group 2) and one (group 3) immunising doses of Ostertagia circumcincta together w ith Trichostrongylus colubriformis. Group 4 sheep were treated with oxfenda zole only. Group 5 sheep served as an untreated controls and nonlactating s heep (group 6) were used as additional controls. These results show that pe riparturient rise in parasite eggs was in the 4-year-old ewes moderate, but significantly decreased either by drug treatment or by drug-abbreviated im munisation. There was a tendency for lambs born from immunised ewes to gain weight more rapidly than lambs born from non-immunised ewes.