Genetics - Vale to a bare-breech trailblazer
A ram whose genes could mimic the effects of mulesing and crutching has died, leaving science a mighty genetic legacy and a major challenge.
Today there are about 95 million sheep in Australia, but one ram alone stood out so much from the flock that his death early this year was chronicled in newspapers across the country. His name was Cojak and he became the reason for a nationwide search for other sheep that bore his trademark trait – a bare backside. It was a mutation, a beautiful mutation, because it precisely mimicked the desired effect of mulesing and crutching.
It was breeders Niel and Pat Smith who in 2002 spotted the significance of their bare-breeched ram, born on ‘Calcookara’, near Cowell in South Australia. The Smiths reported Cojak to researchers at the Roseworthy Campus of the University of Adelaide, who remember receiving the call. “We raced out to the property to take a look,” Professor Phil Hynd says. “It was an exciting find and it kicked off an AWI-supported program to unravel the underlying genetics.”
Within 12 months – the same amount of time it took the ram to produce a 14-kilogram, 21.4 micron fleece – Professor Hynd’s team also confirmed the Smiths’ suspicion: the ram was passing the trait to his offspring. “We tested the progeny and found the trait is as heritable as common wool traits that breeders routinely select for,” he says. “That makes Cojak the first sheep to indicate that a genetic solution to blowfly strike is possible, and this is a major contribution.”
As woolgrowers and stud breeders across Australia were put on alert, more bare-breeched rams were found; enough for a five-year breeding trial by CSIRO and the Department of Agriculture and Food, Western Australia. This study seeks to estimate how long it takes to breed for breech-strike resistance and also determine the trade-offs that may occur with other commercial characteristics, such as fleece weight.
Cojak’s legacy is also being felt at AWI’s Falkiner Memorial Field Station, which is taking part in the biggest sheep gene-mapping project in the world. Dr Troy Fischer, AWI program manager for sheep productivity, is using the facility to identify DNA markers for the bare-breech trait.
Even more strikingly, a large commercial flock of 25,000 sheep in WA was recently identified as having hundreds of bare-breech animals. Even though he is in a 500-millimetre rainfall zone, the WA breeder says he has no flies, no ‘dermo’ (dermatophilosis, or fleece rot) and is marking greater than 100 per cent lambs. When pedigrees were checked, it was discovered that the WA flock is based on similar bloodlines to ‘Calcookara’.
“Given all the scientific work being done on Cojak’s bare-breeched brethren, we can say the sire lives on,” Professor Hynd says. “Despite his death, he is still helping to transform how we go about defending Australia’s flocks against blowfly strike.”
More information: Dr Troy Fischer, 02 8295 3151
See also: Bare-breech rams opening frontiers and The inherent worm resistence of Merinos.
Return to Beyond the Bale Issue 28 index page.