Internal Parasite Management in Sheep
The following article comes from the LHPA website (www.lhpa.org.au/news/best-chance-to-stop-worms-looms). It accurately describes the issues and management required to best control worms and liver fluke in a sheep flock. Following several bad worm years, the Livestock Health and Pest Authorities (LHPA) are encouraging sheep producers to take proactive steps now in order to avoid a repeat of recent disasters.
Over the last few seasons internal parasites have cost many farmers dearly – heavy mortalities, significant production losses and big drench bills have been commonplace.
As the season hots up worm larvae will start to die off. At the same time opportunities to effectively drench sheep onto relatively safe paddocks such as crop and hay paddocks will present the best opportunity to break the worm’s life cycle.
The first step is to measure worm egg counts to see whether your sheep have worm problems. Most worms are not visible in sheep droppings, so testing freshly collected droppings is essential.
The results will identify if there are worms present, the type and amount which will allow the most effective drench to be chosen.
Measuring egg worm counts to determine effective drenching will slow down or prevent resistance building up. Drench resistance can develop through overuse of the same drench family, if the product is used incorrectly, or by bringing resistant worms onto your property through infected sheep.
Each property will have differing drench resistance levels, and the best way to find out which drenches will work on your property is with a drench resistance test. This is best done on weaner aged sheep which haven’t been previously drenched.
Many LHPAs have carried out drench resistance projects with sheep producers. LHPA District Veterinarian Evelyn Walker said of the properties surveyed in the Central West, areas have drench resistance present on every single farm.
"However, drench resistance may be present in only certain worm species. For example, a drench may be effective on the Black scour worm, but not necessarily the Barber’s pole worm. Using personalised resistance information, a farmer can strategically drench based on his worm populations with a product that’s sure to work," she said.
If a full drench resistance test can’t be conducted, a worm egg count test on lambs before and 10-14 days after drenching will indicate how effective that drench is.
The effects of not testing drenches can be long term and expensive. Knowing what drenches work can open up the possibility of cheaper drench groups to use in your rotation.
As well as using correct drenches, strategic paddock management and good nutrition are important. It’s good practice to ensure susceptible sheep, especially weaners, are not placed in heavily contaminated paddocks and provide good quality feed to encourage development of their immune system.
Worm testing kits are available from your local LHPA office and staff can assist with advice on drench resistance and parasite control.