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Beyond the Bale : March 2018
WHAT IS THE CAUSE? The main cause of the loss of immunity is the negative nutritional balance of the late pregnant and lactating ewe. Put simply, ewes generally lose weight during this time and can typically lose 30–50% of their fat and 10–20% of their protein reserves from two weeks prior to five weeks after lambing. While not fully accounting for all the changes that increase susceptibility of reproductive ewes to worms, these losses are the main cause. Increasing the quality of the diet results in lactating ewes eating more and being in better condition and this improves worm resistance and reduces worm burdens. WHAT CAN YOU DO ABOUT IT? Both breeding and management approaches can be used to deal with the increased susceptibility of the lambing ewe to worm infection. These involve increasing immunity or decreasing the worm challenge. IMPROVE THE IMMUNITY OF EWES TO WORMS • All ewes should be in good condition by lambing and have sufficient pasture by following the Lifetime Ewe Management program (see page 36). • In barber’s pole worm regions, vaccinating with Barbervax® can result in ewes better able to kill the worm larvae they ingest; commence a vaccination program well before lambing. • Breed worm-resistant ewes by using rams with more negative Worm Egg Count Australian Sheep Breeding Values (ASBVs). These strategies, in turn, also contribute to fewer worms on the pasture. REDUCE EXPOSURE OF LAMBING EWES TO WORMS • Use a grazing management strategy to provide low worm-risk paddocks for lambing ewes, particularly in spring lambing barber’s pole worm regions. • Remove worms from the ewes just prior to lambing with an effective drench: • A short acting product is generally all that is required, particularly in southern Australian scour worm- areas and anywhere that lambing paddocks have been prepared as low worm-risk. • A long acting product may be indicated if lambing paddocks are known to be heavily contaminated, but take care because: • any long acting product has greater potential for accelerating development of drench resistance • drench resistance of barber’s pole worm to moxidectin (the active in the commonly used long acting injections) is already very widespread (an effective primer drench should be used concurrently) • moxidectin transfers from the ewe to the lamb through milk, resulting in the lamb receiving too low a dose of the active, which may accelerate drench resistance development. Your location in Australia will determine which of these strategies should gain the most focus on your property. But in most regions, late summer and autumn is a critical time to address these in one way or another. WormBoss Worm Control Programs have been developed for eight regions in Australia and describe the recommended strategies and when and how to implement them. MORE INFORMATION www.wormboss.com.au/programs.php ON FARM 57
In the Shops - March 2018