Selection method findings analysed
One of Australia’s longest flock-selection trials has proved that using rams bred from different selection systems improves profitability.
The South Australian Selection Demonstration Flock (SDF) project concluded last year after 10 years of monitoring each selection system by assessing progeny every year.
Funded by AWI and the South Australian Research and Development Institute (SARDI), with support from Meat and Livestock Australia, the University of Adelaide and the South Australian Stud Merino Sheepbreeders Association, the project evaluated and demonstrated the strengths and weaknesses of the various selection strategies typically used in the Merino industry.
SDF principal research scientist Dr Forbes Brien says the fact that the three selection systems provided a higher gross margin than the control flock indicates that when using a breeding objective based on economically important traits, all selection methods can increase profitability of commercial flocks.
“The performance-index selection method returned the highest gross margins regardless of market conditions, increasing GM/DSE/year by up to a dollar per year,” he says.
The first few years of the project saw rapid gains in many traits among the flocks, largely through the use of specially selected outside sires, which enabled the breeding groups to quickly take their flocks towards their breeding objectives.
When matings reverted to using rams bred within the selection flocks, the rate of genetic gain slowed. However, all flocks continued to make progress towards their breeding objectives and, importantly, a range of strengths and weaknesses of each method emerged.
In 1996, the trial began with control, performance-index, classer-assessed and elite-wool flocks; in 2000 a dual-purpose flock was added, and then in 2001 a fine-wool flock.
Fine-wool-flock trial participant Hugh Jarvis, who runs fine-wool Merinos on the 1100-hectare ‘Aramis’, 45 kilometres north-west of Hamilton in Victoria, came to the project with his own enterprise aim of producing 60 kilograms of 18-micron wool per hectare from easy-care, highly fertile sheep with high resistance to internal parasites and flystrike in a wheat/sheep zone.
Mr Jarvis has reduced the micron in his sheep from 24 micron to 18 micron over a 15-year period. “Breeding method is certainly important, but it is also important to keep things in perspective and use common sense in a selection system,” he says. “When the project began, I thought it was good to have proponents of each method with the same opportunity to prove how well their system could meet the breeding objectives.”
To test the capacity of combining the best components of each selection system, the SDF fine-wool flock was established in 2001 and run through until 2005. The breeding objective was to reduce micron, while increasing tensile strength and fleece weight. In other words, breed finer-wool sheep suitable for the wheat/sheep belt.
“Yet very few woolgrowers in this climatic zone have attempted this, due to preconceived ideas about yield and vegetable matter discounts, as well as concerns about the constitution or doing ability of fine-wool sheep,” Mr Jarvis says.
He says the old bogey quickly occurred, with dust penetrating the fleece, reducing style and yield. But he says what was more interesting was the fact that it was quickly resolved by selecting rams with dust-repelling fleece structure.
Mr Jarvis says that as a result of working alongside the elite flock, he is now looking to improve staple strength by seeking wool with well-defined, even crimp and finer follicle bundles, as well as by measuring staple strength. “And working with the professional classers helped my capacity to target visual traits including feet, frame and mouths,” he says. “In my own breeding program, I’ve also had a focus on selecting sheep for low worm-egg counts, and this has resulted in a near-halving of the amount of drench I’m using.
“And we’ve also altered our shearing time so that it now occurs before harvest, to fit in with the increased cropping program and to reduce the amount of dust in the wool.”
Further grower insights into alternative selection systems are now available in a brochure, Merino Breeding for Profit, which outlines the SDF findings.
More information: Merino Breeding for Profit is available from the AWI Helpline, 1800 070 099, and can be downloaded from the AWI website, www.wool.com.au/publications
Key project findings
Breeding and selection
- Breeding better sheep increases stud and commercial producers’ profits.
- Different selection methods will lead to different levels of profit.
- Breeding goals that focus on long-term profit bring profit, regardless of the selection strategy.
- Breeding goals need to take into account all important traits, including visual and measured traits.
Monitoring and measurement
- It is important to monitor changes in all traits, including visual and measured traits, and all selection strategies benefit from monitoring.
- All selection methods can substantially improve visual wool-quality and skin traits.
- Placing a strong emphasis on wool traits such as fleece weight and fibre diameter does not affect conformation.
Genetics
- The introduction of genetic material from outside sires can result in rapid and profitable changes.
- The superiority of sheep selected at a young age is maintained through their lifetime.
Image: Victorian fine-wool grower Hugh Jarvis, a participant in the SDF project.
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