Survey confirms slow adoption of orange and purple wormers

Fewer than one in five sheep farmers are following industry best practice around group four and five wormers, a survey has revealed.

An audit of wormer protocols on 370 farms released by Elanco last month found a significant proportion unwittingly contributes to parasite resistance.

This is done by neglecting to use new active orange Zolvix (monepantel) and purple Startect (Derquantel and Abamectin) wormers.

See also: Sheep wormer made more widely available to combat resistance

The study adds weight to industry fears about the cost of monepantel being prohibitive and some farms avoiding its use now so it is there for them in the future.

But Farmers Weekly understands there is a need for farms to use Zolvix judiciously, or risk losing the active as a commercial product. The product was made more accessible in 2017, when it became available through merchants rather than vet only.   

Critically, the active must be used carefully for two purposes, said independent sheep consultant Lesley Stubbings:

• To kill parasites in incoming sheep as a quarantine drench
• As a late summer “knock-out dose” to treat worms resistant to the other anthelmintics (white/yellow/clear) used earlier in the season on the farm

Optimal use of group four and five products is important for productivity because resistance to groups one, two and three is becoming increasingly widespread.

“When we look for resistance, we find resistance to the group one BZ (benzimidazole) on nearly every farm,” said Ms Stubbings.

She added that resistance is an insidious process that goes on for years. It cannot be stopped, but it can be slowed by using Zolvix and Startect to kill parasites resistant to the older groups.

“We are not saying that worm control is not important, it is, but we need to use wormers at the right time for the right reason in the right way.”

Anthelmintic alternatives

Ms Stubbings referenced Sustainable Control of Parasites in Sheep (Scops) as an online resource for sheep farmers.

She said there were a host of ways to control worm populations detailed on the Scops website:

• Weaning: Weaning lambs (from about 12 weeks old) and moving to less heavily contaminated grazing can avoid high levels of infectivity. Silage and hay aftermaths that have carried cattle since turnout are ideal
• Grouping lambs by age: Tight age groups increase the usefulness of faecal egg counts, withdrawal periods and marketing
• Mature ewes: Mature sheep in good condition can reduce pasture contamination by ingesting large quantities of infective larvae and killing them off
• Mixed grazing: Grazing cattle and sheep together reduces the stocking density of the host (the sheep)
• Nutrition: Many farms have stopped worming ewes, and some only treat sheep with a low body condition score.. High levels of undegradable protein in the late gestation diet will lead to fewer worms being produced
• Alternative and bioactive crops: Grazing on “bioactive” forages such as chicory, bird’s-foot trefoil and sainfoin reduces the negative effects of parasites in sheep
• Targeted selective treatments: Weighing lambs and targeting those with the lowest daily liveweight gains can reduce overall use in the flock