Using genetics as a tool for increasing host resistance


Ram sales have begun around the country and now is an ideal time to think about the genetic direction of your flock. The Wormwise principles recognise that there are differences in animals in their susceptibility to parasites. These characteristics of host resistance (ewe resilience / parasite tolerance) can be identified and the level of inclusion will determine the benefit in your flock.  Remember, the more selection pressure that is placed on these characteristics, the faster the genetic gain will be.

So how can these characteristics be identified? You can begin by asking your maternal sire breeder if they are using any tools to distinguish rams that require more drenching than those that don’t. This may include FEC monitoring during summer and autumn and identifying those rams that require additional drenching. Some breeders go so far as to not use rams that require a certain number of drenches.  Others may have a no ewe drench policy.

You may have also heard some breeders use the terms WormFEC and WormFEC Gold. WormFEC Gold was created to identify those breeders who are making progress in breeding for resistance to internal parasites. Many others are selecting for host resistance and resilience genes but you may want assurance that it is being done in a meaningful way.

Your main decision is whether the objectives of the breeder match your own. 80% of your flocks genetics are contributed by the ram, so it is an important decision to find a breeder that fits your objectives and then purchase those individual rams that excel in the areas that are most important to your flock. There are excellent tools available on the Sheep Improvement Limited (SIL) website to identify flocks and rams with these characteristics.

Breeding sheep that require fewer drenches it is another tool that will help reduce pressure on the existing drenches that we have. For more information on this and other tools, attend a Wormwise workshop and visit the Wormwise website. Any large changes to your system would be best discussed with your animal health advisor to ensure you develop a plan that will work on your farm.