Warm, wet weather heightens parasite risk in sheep and cattle

The latest NADIS Parasite Forecast, sponsored by Boehringer Ingelheim, highlights that the recent warm, wet weather heightens the risk of parasites in sheep and cattle.

A key component of a farm’s sustainable parasite control programme is forward planning to provide “safe grazing” right from the start of the grazing season.

One benefit is that lambs grazing safe pastures with ewes shouldn’t need worming until after weaning. Ideally, wean lambs onto silage or hay aftermaths that 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, said: “Lambs grazing permanent pasture usually require worming to limit build-up of infective larvae later in the season (‘mid-summer rise’).

“When lambs are dosed, delay any move onto aftermath to allow the treated flock to become lightly re-infected with worms that were not exposed to the wormer, diluting any worms within the lambs that survived treatment and so reducing selection for resistant strains of worms.”

Timing of the move and need for worming treatment(s) for lambs will depend upon grazing history, levels of contamination by periparturient ewes, stocking density and prevailing weather conditions.

Ms Timothy added: “Moving weaned lambs onto aftermaths during July and August can reduce the risk of parasitic disease. This simple management practice reduces exposure to the high larval challenge that can build up on pasture. This is one of the most critical components of sustainable parasite control.”

Strategic worm control in cattle is usually applied to autumn or winter-born weaned calves in their first grazing season, and in spring-born beef suckler calves in their second grazing season. Wormers should always be administered following the COWS 5 R’s principles – right product; right animal; right time; right dose; given in the right way.

Ms Timothy said: “Calves in their first grazing season are most at risk of disease, and heavy worm burdens will cause ill-thrift and potentially severe scouring. Not only that, we know that gutworm has a potential impact on future performance, particularly fertility. Sub-clinical growth checks mean heifers take longer to reach target weight for first service, and can take longer to get in calf, with multiple inseminations often required.”

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