THERE ARE five main groups of wormers available, with three widely used. White and yellow drenches have been around since the 1960s, clear drenches and injectables since 1982, Zolvix since 2008, and Startect since 2010.
There is very little in the difference in price between the standard clear, white or yellow wormers, especially if you are dealing with lighter stock and lambs. If a farmer establishes through a faecal egg test that the flock has no resistance to clear doses such as moxidectin or doramectin, then these macrocyclics are a good option since they have are more persistent and kill a wider range of parasites, including stomach, lung and external parasites.
The ideal scenario is to use a white drench early in the year to treat Nematodirus. If a subsequent faecal egg test shows that there is still a worm burden in the flock, a clear dose such as Cydectin is a good next step. Lambs might need two doses of Cydectin prior to slaughter, but make sure that you keep an eye on the 14 day meat withdrawal period that goes with this product.
If you cannot afford to take any chances, a product such as Startect is best as it is broad spectrum and has no known resistance in Ireland.
A triclabendazole such as Fasinex remains the best flukacide, but in the west of Ireland this product has been 'broken' due to over-use of the drug. This highlights the importance of alternating between drug types and not just brands.