Scientists a step closer to an alternative to conventional anthelmintics
Take Home Message: Dosing grazing lambs with tannins tends to reduce faecal worm egg counts and increases daily liveweight gain, but not as effectively as conventional wormers.
The use of quebracho tannins could become an effective approach for the treatment of intestinal parasites, particularly with the increasing prevalence of resistance to conventional anthelmintics. “But more work is needed to develop optimal dosing and management regimens with tannins,” Dickon Hovell told delegates at this year’s British Society of Animal Science’s annual conference.
Sheep producers have become heavily reliant on anthelmintics for the control of nematode parasites, but due to the widespread development of anthelmintic resistance, alternative approaches for control of nematode parasites are needed.
A recent study of commercial lambs treated with quebracho tannin reported reduced faecal egg counts and improved lamb growth. Dr Hovell and his team at Aberdeen University carried out a second study with quebracho tannins at higher dose rates in lambs.
A total of 60 male and female Suffolk cross lambs, of between seven and eight months old, were chosen randomly from a group that had shown symptoms of internal parasites 14 days prior to the start of the experiment. They were kept in an 11-acre field where they were free to graze on grass or kale, no concentrates were fed and they had free access to clean water at all times.
Exactly one week before the first dosing, the lambs were brought inside to the sheep handling system where all husbandry activities were carried out. Lambs were individually weighed, and randomised to one of five groups with 12 lambs in each.
The following week all lambs were weighed, the first administration of wormer was given, and faecal samples taken from three identified lambs from each group. Lambs were weighed and faecal samples taken (from the same three lambs) at one-week intervals for six weeks. The Quebracho Tannin was the same as that used in the previous study and was mixed with water at 40ºC, and orally administered by conventional dosing gun.
The five different treatments were: dosed once with 60g of tannin; dosed twice with 60g of tannin, the second dose given a week after the first; dosed once with 90g of tannin; dosed once with a conventional anthelmintic, ‘Zermex’ containing the active ingredient Moxidectin belonging to the Ivermectin group; untreated control.
“The trial revealed that lambs dosed with Zermex had a lower faecal egg counts (FEC) than the control, although this was not always statistically significant,” said Dr Hovell. “There were no significant effects of quebracho tannins on FECs, although there was the suggestion of a decline in FECs of Trichostrongyloidea. Treatment with Zermex gave the best weight gain of 12.5 kg.
“But there was a clear growth response to the tannin, despite there being no clear effect on FECs,” added Dr Hovell.
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