of the RSPCA is that Australian merino sheep have not been ethically bred, as seen in their susceptibility to flystrike. They believe "any painful procedure to change the breech area should only be considered an interim, short-term solution that accompanies a breeding program that focusses on flystrike resistance, and is carried out only where absolutely necessary to manage at-risk sheep." Breeding programs Merino sheep bred on selection principles may be more resistant to flystrike because they are plain bodied (lower skin wrinkling around the breech). Studies have shown that flystrike is lower in plain bodied sheep. However, mulesed animals had consistently lower flystrike than unmulesed regardless of body type. The resistance of plain-bodied Merino sheep to flystrike arose from field investigations by Australian scientists, Drs H.R. Seddon and H.B. Belschner, in the early 1930s. Non-mulesed Merino ewe bodies were graded as plain (A class), wrinkly (B class) and very wrinkly (C class). The plain-bodied (A class) Merino ewes were much less susceptible to flystrike than wrinkly-bodied Merinos (B and C class). In these Merino flocks, the sheep are plainer than the plain-bodied (A class) Merino ewes and therefore more resistant to flystrike. The rams and semen from these studs are used in over 3,000 of the 45,000 Merino farms in Australia. Using breeding principles, wrinkle-skinned Merino flocks which require mulesing have been transformed into plain-bodied and mules-free flocks within five years. Non-surgical alternatives Several non-surgical alternatives are currently being researched: Insecticides: Any number of insecticides are now available for prevention of fly strike, and even early reviews proclaimed the effectiveness of using dip across the whole animal, rather than cutting one small portion that left the rest of the animal still susceptible "dipping is still the most cost effective means of protecting sheep from flystrike". Topical protein-based treatments which kill wool follicles and tighten skin in the breech area (intradermal injections) Biological control of blowflies. Plastic clips on the sheep's skin folds which act like castration bands, removing the skin (breech clips). Tea tree oil as a 1% formulation dip where tests have shown a 100% kill rate of first-stage maggots and a strong repellent effect against adult flies, which prevented eggs being laid on the wool for up to six weeks. See also Agriculture in Australia Docking Overview of discretionary invasive procedures on animals References Livestock in Australia Cruelty to animals Animal welfare Sheep