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DNA tests fast track genetic gain at Merinotech WA

Thursday 15th of October 2015
Ian Robertson, Merinotech WA
Ian Robertson, Merinotech WA

The use of DNA testing has fast-tracked genetic improvement in the flock of Merinotech WA, which will be almost entirely polled by next year - 20 years faster than expected. The move is paying dividends in meeting the needs of their clients, with commercial ram buyers demanding polled rams over those with horns and nearly all their eastern states and New Zealand customers only purchasing semen from pure poll rams.

Manager of Merinotech WA’s elite flock, Ian Robertson, said the quest for a pure poll flock began about eight years ago and would have taken another two decades if they had continued to use conventional selection methods. “Instead it’s going to take just three or four years since we began using the DNA testing,” Mr Robertson said. “The tests really accelerated our program because previously about half of the sheep that visually looked pure poll were in fact carrying the horn gene (PH).

“For me it’s a waste of time producing a PH ram – pure polled rams are really where the demand lies. The money is in guaranteeing to our customers that we’ve got high-ranking PP rams. “Our daughter studs are also reporting that their clients only want pure polled rams and our semen sales are only PP these days.”

Use of homozygous or ‘pure poll’ (PP) rams allows producers to dramatically reduce the number of animals born that carry a horn gene. The poll gene test was developed by the Cooperative Research Centre for Sheep Industry Innovation (Sheep CRC) and is more than 95 per cent accurate.

Sheep CRC researcher Tom Granleese has been assisting Merinotech WA in developing its testing strategy and breeding program, increasing the rate at which they have been able to reduce the frequency of the horn gene at the lowest cost.

Merinotech WA is currently DNA testing 50-70pc of the lamb drop in a bid to quickly achieve a pure poll flock, while maintaining the right balance of productive traits. The ram lambs are tested using the 12K SNP chips (previously 50K) for a full genomic analysis, while the ewe lambs are only having the Horn/Poll test done.

“This year we will also test the full ewe flock with the Sheep CRC’s $17 Horn/Poll test – half of those that fail the test will be retained as recipients for our embryo transfer program but the rest will be culled,” Mr Robertson said.

“We should have a full drop of pure poll sheep in our next drop and from there on we should see some fairly exciting improvements in our genetics as we progress towards using ram lambs and increase the size of our embryo transfer program.”

Once a pure poll flock is achieved, the rate of genomic testing using the 12K SNP chip will be reduced to just 18pc of the ram lamb drop. Together with their extensive flock records and full pedigree recording, this will allow Merinotech WA to identify the right genetic combinations to continue delivering an average rate of 20pc genetic gain per year.

MerinotechWA is an intensively recorded Merino ram breeding system. Its ‘Elite Flock’ joins 540 stud ewes each year in single sire matings using a group of 11 young rams, while the 10 best ewes are selected for an embryo transfer program yielding eight lambs per donor ewe on average.

The Merinotech WA daughter studs provide the bulk of the rams to their 50 commercial clients, and this year will supply more than 400 rams.

They also measure wool, meat and worm resistance traits for each yearling, which are sent to MERINOSELECT to calculate trait ASBVs (Australian Sheep Breeding Values), which are incorporated into the Merinotech WA Index score to help select their rams for sale.

Mr Robertson is gradually introducing ram lambs to his breeding program with three to four ram lambs next year being joined with 35 ewes each, and plans to double the size of the ET program. These ram lambs will be chosen using their genomic breeding values and visual assessment.

“We use measurement, visual assessment, full pedigree recording and the latest genomic research and reproductive technology available to make genetic improvement as rapidly as possible,” Mr Robertson said.

“We have a very highly tested flock and we have full pedigree so our figures are very accurate. That gives us a sure bet for accuracy at selection. Even as lambs we can accurately predict what their adult wool cut or eye muscle is going to be.”

The use of their extensive data to add selection pressure over time has pushed their ASBV scores into the top one percent of the breed on the MERINOSELECT Dual Purpose Index.

The horn/poll and parentage DNA test is available for $17 per test at www.sheepcrc.org.au.

Media contact: Michael Thomson on 07 4927 0805 / 0408 819 666

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