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Breeding for parasite resistance - BTB July 2007 |
Strap: Case study
Head: Breeding for parasite resistance
Precede: With 16-years experience using genetic breeding tools, Andrew Burgess discusses the impact of selecting for worm resistance on the operation of Ruby Hills. By Gio Braidotti
On Ruby Hills’ 2000 hectares in New England, NSW, Andrew Burgess breeds his own rams and runs 5000 fine and superfine Merino ewes, in addition to 1000 cross-bred ewes for the lamb market.
Some years ago, Mr Burgess did a business analysis and identified the property’s biggest problem as the cost associated with delivering animal health remedies, with worms, in particular, eating into farm profits.
He admits that he was initially sceptical when the case was made that a breeding program could be used to embed worm resistance into his sires and flock.
“At first I thought it was crazy but the worm problem was out of control and the more we thought about it, the more prepared we were to give it a go,” says Mr Burgess.
Back when he started, breeding for worm resistance relied exclusively on faecal egg counts (FECs), a measurement that initially proved highly variable, as changing weather and pasture conditions affected parasite numbers independently of sheep genetics. These days, in contrast, sires and semen with proven and heritable worm resistance are readily available resources.
“Finding resistant animals using FECs back then was like looking for a needle in a haystack,” he frankly admits. “The repeatability of the measurements was low but we plugged away – we had to. The worm problem was out of control.”
It took a while, but worm resistance is a quite heritable trait – eventually the benefits of the breeding started kicking in.
“Worm resistance is now so strongly embedded in the flock that we have no problem whatsoever finding resistant animals with very good production traits,” says Mr Burgess. As a result, Ruby Hill is seeing ever fewer situations where the stock is “really wormy”.
“Even in the last couple of years, when the weather created horrendous worm conditions, the flock stood up really well. The impact of all that selective breeding is starting to be noticeable.”
He insists that getting started today is far easier – genetic data, sires and semen are now readily available through the national database, Sheep Genetics Australia (SGA). As to the charges associated with using SGA, he describes them as irrelevant: “The cost of getting the genetics right is miniscule compared to the benefits in wool sales.”
Having accumulated a total of 16-years experience with genetic calculations, Mr Burgess views breeding values as a way to ensure Ruby Hill’s continued profitability. In all, he uses SGA to work on around five traits in addition to worm resistance.
“With wool it can be a bit of a juggling act,” he says. “For example, with a premium being paid for staple strength – a trait that has a genetic component – I’ve been making some changes and shifting the emphasis on the most profitable combinations.”
So even with the feed situation on a knife-edge because of drought – a situation that has the farm at 65 per cent of optimum carrying capacity – Mr Burgess continues to maintain his breeding program and to finetune his breeding objectives.
“We recently had rain but too late in the season. Now the cold is limiting pasture growth and it may be a struggle to get the stock through winter without feeding. But we keep the genetic breeding going. We look at it from a long-term perspective and the progress we’ve made has been extraordinary.”
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