SHEEP producers have been warned to avoid using sheep capsules to help extend drench group effectiveness.
Rural retailers and Hamilton veterinarian David Rendell are also concerned sheep producers might substitute worm capsules with a drench group ineffective for the worms in their flocks.
Merial Australia has said demand for its Abamectin-Albendazole sheep capsule Dynamax is well above what it can supply. A similar capsule Bionic is only available through CRT stores, but not Dynamax distributors. Demand for Merial’s entire sheep capsule range, including the Maximizer and Extender capsules, is double that of the previous six years.
Dr Rendell believed Extender 100 (albendazole) and Benzimidazole (BZ or white drench) capsules were still effective on some properties, particularly if an effective primer drench was given when inserting the capsule.
“Ivomec capsules I believe are high risk given the degree of Ivomec resistance.”
His records last year indicated 86 per cent of farmers without an integrated worm management program had some Ivomec resistance in their flocks.
“Out of 30 random faecal tests last year non-client flocks, 86 per cent had Ivomec resistance and the 2011 results thus far are even worse.”
He said there was also considerable risk with using Ivomec-BZ capsules.
Dr Rendell said capsules generally were very effective products when there was no worm resistance in flocks to their active ingredients.
If producers did not need to use capsules, the longer they could put off their use, the longer drench groups would be effective, he said.
“You can’t have a chemical exposure for 100 days all winter and get better worm control and not get more resistance.
“Either the capsules don’t give better worm control and you don’t get resistance or by giving you better worm control they are killing the good guys (less resistant worms).
Sheep are also more vulnerable when the effectiveness of capsules wears off and some of the benefits gained during capsule pay-out are then lost, he said.
“If you have vulnerable sheep at the end of the capsule period of effectiveness then look out.”
Dr Rendell said the capsules most likely to work in most flocks now were Dynamax or Bionic, as they are the same product, though effectiveness was not always assured.
He believed the Abamectin-Albendazole products were more effective as each tablet contained a full dose of abamectin and BZ, whereas Ivomec BZ capsules have alternate tablets of each product.
“Abamectin is more potent than Ivermectin.”
Dr Rendell said the benefit of capsules is going to higher in younger low condition score animals than in older, good conditioned sheep.
“This year most mature sheep are in good condition so the benefit will be well back.
“So I think people are panicking over worms this year and running around using capsules because they have a high cash flow and because of the wet summer,” he said.
“They don’t need to be quite so worried and should be a bit more judicious in use of the product.”
Dr Rendell said lambs with high faecal worm egg counts over summer would give producers less problems this winter as they lambs would have developed strong immunity provided they are above target liveweights.
Factors such as pasture feed available and condition score were equally important as egg counts and worm levels in mature sheep, he said.
“If the feed levels are high and condition scores are in the high 3s then the benefit in drenching is way way down.
“If their condition score is less than 2.7 and the feed levels are low then drenching requirements escalate, as does the benefit of a capsule,” he said.
“If you do your maths two drenches of Tri-Guard, Hatrick or Pyrimide - pre and post-lambing - and four lamb drenches are still less than the price of the capsule and one or two lamb drenches.
“I think that using lots of capsules is a sledgehammer approach.”
Email a friend