Vets warn of raised worm risk in sheep as weather warms up

The National Animal Disease Information Service (Nadis) and Merial Animal Health has warned that warmer temperatures than average may raise parasitic disease risk this spring and summer.

See also: Drench calculator shows cost of wormer resistance

However, they said worm treatment timings would depends upon prevailing weather conditions, grazing history, contamination levels and stocking density.

Sioned Timothy, veterinary adviser for Merial Animal Health, said: “Prolonged dry weather conditions during the spring may have delayed the larval challenge, but infectivity will increase once wetter weather returns and leave lambs susceptible to parasitic gastroenteritis (PGE).”

Animal health experts recommend weighing lambs every three to four weeks to identify the poor performers and target them for worming treatment.

Dosing only  animals with poor growth rates can be a simple way to save on wormer treatments and combat wormer resistance.

Reducing wormer use

  • Wormer treatment recommended at 500-700epg
  • Weigh lambs every three to four weeks to spot poor doers

Wormer questions

My lambs are on silage aftermaths that didn’t have sheep on earlier this year – are they OK?

Lambs on safe grazing at the start of turnout shouldn’t need worming until after they are weaned. Ideally, lambs are put on to hay or silage aftermaths that are clean.

My farm is permanent pasture – what is the disease burden here?

Usually, lambs on permanent pastures require wormers to limit the build-up of infective larvae later in the season. Monitoring weight regularly and faecal egg counts (FECs) from June onwards can guide anthelmintic treatments. 

Is this only a problem in lambs – what about breeding stock?

Ram are fully susceptible to parasitic gastroenteritis and frequently forgotten about. Fertile rams need to be in good condition at tupping (3.5 BCS) and two months of good grazing can be needed to gain one unit of condition score.