Flystrike (cutaneous myiasis) causes severe suffering in sheep, and breeding approaches that reduce susceptibility offer a welfare-improving alternative to reliance on chemical prevention.
Flystrike causes extreme suffering — maggots secrete proteolytic enzymes that liquefy and consume living tissue, causing painful wounds that can become extensive within 24 hours. Affected sheep show distress, separation from the flock, and rapid deterioration. Genetic selection for resistance traits reduces the frequency and severity of flystrike, with welfare benefits for every generation of sheep descending from resistant stock. This approach addresses the root cause — skin fold depth and dag accumulation — rather than treating consequences. New Zealand's industry-wide shift to resistance breeding demonstrates the commercial feasibility of this welfare improvement.