One of the major inhibitors to the profit of the Australian sheep industry is flystrike of the wool in the breech area of the sheep. The wrinkled skin and the thick wool become soiled with faeces and urine and provide a moist environment for the blowfly to lay its eggs. Blowfly larvae have calamitous effects on the sheep and often end in the death of the sheep infected. At present the only methods for preventing flystrike are strict management methods and a number of procedures always including one in particular, mulesing. Mulesing is a procedure where the skin folds on the breech of a sheep are removed to tighten the skin thus, in conjunction with regular crutching, prevent soiling of the breech. Mulesing can often be combined with tail docking, or simply the removal of the tail, this helps further prevent flystrike in the breech area.
This method, although effective has come under heavy criticism from many animal rights groups. And after consistent pressure the Australian sheep industry has announced their efforts to phase out mulesing completely by 2010.
This decision to ban the procedure had bought significant pressure upon the sheep industry to find an alternative to mulesing. The timely discovery of a possible ASBV for a bare breech phenotype among many researchers all over Australia may be the answer. ASBV stands for Australian Sheep Breeding Values. It is simply an estimate of the genetic potential a sheep will pass on to its offspring. This is a nationwide code for genetic comparison of sheep and are available for many traits such as wool quality, growth rates, parasite resistance and now possibly for breech wrinkle and breech cover. More research is needed to develop them from simple EBVs (Estimated Breeding Values) to full ASBVs but experiments are showing promising results so far.
Traits are scored on a scalar score usually from 1-5 but sometimes it can change. Using the bare breech phenotype for example, a sire (ram) with a score of 1 would yield the least breech wrinkle and the least breech cover and a 5 the most breech wrinkle and cover. Breeders are encouraged to make use of sires with low ASBVs for breech wrinkle and cover and this will most likely yield these traits on the progeny. By using intensive selection in breeding the Australian sheep industry may be able to produce sheep with flystrike resistance comparable with mulesed sheep thus eliminating the need for mulesing furthermore.
Rhett Mitchell - BBC
References:
Sam Gill, Feedback - Meat and Livestock Australia, March/April edition 2009
Luke Stephen, Kondinin Group
