Selective breeding for resistance to gastrointestinal parasites in sheep offers a long-term welfare improvement by reducing disease burden and the need for anthelmintic treatment.
Parasite resistance breeding represents a long-term, sustainable welfare solution that reduces both disease burden and anthelmintic treatment frequency. Heavy worm burdens cause progressive anemia, bottle jaw from protein deficiency, weight loss, and death in severe cases - significant welfare harms. The growing resistance of worms to available anthelmintics makes genetic resistance in the host increasingly important. Selecting for FAMACHA score and worm egg count responses enables genetic improvement toward more resistant sheep that require less treatment and experience less disease. This approach benefits welfare while also protecting the anthelmintic tools remaining available.