Livestock farmers looking to develop a sustainable parasite control programme should be looking to forward plan to provide ‘safe grazing’ throughout the grazing season.
One benefit is that lambs grazing safe pastures with ewes should not need worming until after weaning.
Lambs should, ideally, be weaned onto silage or hay aftermaths which have not been grazed by sheep earlier in the year. By mid-summer any over-wintering larvae will have died off and fields can then be considered ‘safe’.
Sioned Timothy, ruminant technical manager at Boehringer Ingelheim, says: “Lambs grazing permanent pasture usually require worming to limit build-up of infective larvae later in the season.
“When lambs are dosed, delay any move onto aftermath to allow the treated flock to become lightly re-infected with worms which were not exposed to the wormer, diluting any worms within the lambs which survived treatment and so reducing selection for resistant strains of worms.”
Where aftermaths are not available, performance monitoring using growth rates, or worm faecal egg counts (FECs) on lambs every two to four weeks from June onwards, can be used to guide anthelmintic treatments.
Pooled faecal samples from about 10-12 lambs in a group can be used for FECs and will help guide the need for treatment.
Follow SCOPS recommendations by leaving some lambs untreated and monitor treatment efficacy by performing a drench test post-treatment.
Cattle receiving strategic anthelmintic treatments in the early part of the grazing season should remain on the same pasture for the entire grazing season or be moved to safe pastures, such as aftermaths, as they become available.
Ms Timothy says: “Calves in their first grazing season are most at risk of disease, and heavy worm burdens will cause ill-thrift and potentially severe scouring.
“Despite popular misconception, adult cows will become infected by gutworm, though they carry lower worm burdens, shed fewer eggs and do not show outward signs of disease.”