Sheep Blowfly Strike Genetic Resistance

Genetic selection for resistance to blowfly strike in sheep offers a long-term welfare solution to one of the most painful and economically costly conditions in UK and Australian sheep farming.

Key Facts

Blowfly strike affects an estimated 80 percent of UK sheep flocks in at least one sheep per year
Lucilia sericata is the primary blowfly species in UK and Phaenicia cuprina in Australia
Genetic factors including skin wrinkliness, wool characteristics, and dag accumulation influence susceptibility
Estimated heritability of flystrike susceptibility is moderate, making genetic selection feasible
Breech modification including plain-bodied Merino selection has reduced flystrike rates in New Zealand
Integrated control combining genetics, preventive treatments, and management offers the best outcomes

Welfare Considerations

Blowfly strike causes one of the most acutely painful conditions in domestic sheep. Maggot infestation of living tissue causes severe suffering through tissue destruction, toxin absorption, and pain from the expanding wound. Untreated strike can be fatal within days. The ability to genetically reduce susceptibility through selection for resistant traits provides a long-term welfare solution that reduces the number of animals suffering this condition in future generations. Genetic progress towards resistant flocks, combined with targeted preventive treatment and monitoring, progressively reduces the welfare burden of blowfly strike at population scale.

What You Can Do

Discuss genetic selection for blowfly strike resistance with your vet and flock adviser
Use estimated breeding values for flystrike resistance in ram selection where available for your breed
Participate in flystrike recording and genetic improvement programmes run by breed societies
Combine genetic improvement with targeted preventive treatment to reduce overall flystrike incidence
Support research into heritability of flystrike resistance traits in UK breeds