With resistance to anthelmintic drenches becoming a more widespread problem and questions over the environmental impact of their use, the sheep sector needs to start looking for other alternatives to allow profitable farming to continue. Genetics is the answer.
Resilience to gastrointestinal nematodes (parasitic worms) is a relatively new concept for the UK but is a very simple one. A sheep defined as resilient is one which continues to survive and thrive, despite its parasitic burden. This is not to be confused with animals described as resistant to parasitic worms, which are defined as animals which have a lower parasitic burden, due to their ability to produce an antibody immune response against the parasite. Worms may also evolve resistance to the sheep`s immune response in the same way that they have evolved resistance to drenching, risking the creation of a “super worm”.
Resilience (or tolerance) to worms is possibly the “natural state” achieved over thousands of years of evolution. Worms don’t want to kill their sheep host but coexist with them. When we invented affective anthelmintics we took our eye off the ball when the genetic adaptation of sheep to worms was concerned. Now as wormers fail to work, we need to fall back on these natural traits. A sheep that is resilient to worms does not challenge the worms but copes with the infection and grows despite the worms. Good production is what we farmers want, and this way we don’t need to be concerned about worm egg counts or resort to blanket worm treatments. We can measure production and trust our sheep to cope with the worms, with only the poorer-performing sheep requiring treatment.
We were keen to validate our approach so took up the opportunity to work with, The Castle Veterinary Group, the Moredun Foundation and CIEL as part of Defra’s Farming Innovation Programme managed by Innovate UK. This has allowed us to dig deeper into worm resilience and how we can improve heritability in our flock. Please follow this link to learn more.