Technology speeds up genetic gain

The St Leger team: Matt Evans, Heather and Rick Spence.

01-10-2009 | Marie Taylor

Gisborne ram breeder Rick Spence, of St Leger, has the most consistently accurate DNA parentage results year on year.

Pfizer Animal Genetics' regional manager of technical services Sharl Liebergreen says St Leger has parentage results at around 95%, and they manage it without EID.

This is a good example of the attention to detail paid on the Gisborne hill-country property, where Rick has been breeding rams since 1979.

He's an enthusiastic early adopter of new technology, and uses almost every tool available to speed up genetic gain in the flocks. He estimates each of the 900 rams they sell each year costs $230 on technology inputs alone.

He and his wife, Heather, farm Gisborne hill country alongside the Hangaroa River about an hour southwest of the city.

About 60% of their stock units on their 1008ha (950ha effective) farm are sheep, the rest a flexible trading beef system.

Rick spent nine years on the Southern North Island Sheep Council, with three of those as chairman. This was a great introduction to national research projects and the scientists doing the work.

He was concerned about the long-term impact of tagging lambs at birth, at disturbing the birth process and ewe and lamb bonding. He also worried about the uncompetitive nature of single-sire mating, which creates the risk of masking and promoting less active sires.

Five years ago he decided to change from tagging lambs at birth to DNA parentage identification, and to stop using any drench on mixed-age ewes.

To get this rolling, he started DNA profiling the two-tooth ewes born in 2003 and their progeny. Now, except for 160 older ewes, every one of the 3800 ewes on the farm has a DNA profile.

The St Leger team is made up of four full-timers: Rick, Heather, who looks after data entry and records, stock manager Matthew Evans, who has been with them for nearly seven years, and shepherd Ryan Sayer, one of the first batch of cadets to come from the Waipaoa farm cadet scheme.

Rick counts Ken Moore as part of the team, too. Ken is an SIL service provider with NZ Performance Recording Services in Christchurch, and they have worked together since 1999 when the St Leger Studfax database changed over to SIL.

Technology works year round at St Leger, starting with decisions about sire rams in March.

AbacusBio Ani-Mate is a computer programme designed to minimise inbreeding and maximise genetic gain.

"It's a fantastic tool for a large-scale stud," Rick says. Ani-Mate allows them to mate the best ewes to the best rams, and to maximise genetic gain with the least amount of relatedness.

They use it to create the ram teams and ewes to mate them with, with five or six rams for each group of 500 ewes.

The next step is pregnancy scanning in July. At this stage ewes have tags recorded, the litter size, and then the estimated foetal age which gives a birth rank and birth date for that ewe's progeny.

Dries are drafted out and the ewes all mobbed up and run together until spring.

Lambing starts in mid-September, and is strictly a hands-off process for the St Leger team. "We don't go into the paddocks; we only look over the fence." This undisturbed lambing also keeps the flock under commercial pressure.

The flock usually has a 140-150% lambing, depending on the season.

At docking in mid-October, each lamb gets a numbered tag in its ear and a blood sample is taken from the stump of its tail. The samples are sent off to Pfizer for DNA profiling as part of its Shepherd programme.

At the same time, for each paddock, each ewe tag is recorded and any wet/dries noted. This information is uploaded to Pfizer's Shepherd programme, and it's where the 95% accuracy comes in.

The next step is to weigh all the lambs at weaning in mid to late December. There aren't any special crops for the lambs; they just graze the usual pastures.

"They are all treated the same. They are under commercial pressure which lets us sort out the hierarchy of relative growth rates."

They are shorn early in January and weighed again in February. These autumn 200-day lamb weights are sent to Ken Moore who processes the figures for Sheep Improvement Ltd (SIL), which creates dual-purpose indexes.

These are a measure of additional genetic merit above an average, but put into dollars.

Ten years ago when Rick and Heather first used SIL their top rams had a dual-purpose index of around 400. Now their top rams' indexes range from 1000 to 1300 and higher.

That means the top rams now are three times as good in terms of genetic merit. And the progeny from these top rams, measured in cents per ewe mated, will each be $10-$13 in terms of commercial value ahead of the 1995 St Leger average, Rick says.

When they get the indexes back they set a cut-off index below which no animals are retained. Up until this stage all the lambs are kept, even those marked cull for various reasons, because they need to capture all the information from the total lamb crop.

At this time of the year the lamb's DNA sample is analysed with Pfizer's WormSTAR programme. This identifies animals which genetically have greater resistance to parasites and higher productivity.

"Knowing the animals carrying this gene shed fewer eggs on pastures, can grow well in the presence of parasitic challenge, and lead to permanent improvement in the natural resistance of flocks is important."

In the past cull animals were cut and measured to check on carcase composition, but now the 350 ram hoggets ranked highest on SIL's dual purpose index are eye-muscle scanned.

Then in May the 55 with the highest eye muscle area are trucked south to Invermay near Dunedin for more scanning.

InnerVision, a joint venture between AgResearch and Landcorp Farming, has a CT scanner which takes six pictures through the body of each ram, measuring meat, fat and bone.

The ram hoggets with the best carcase composition and value, and meeting other selection criteria, become sire rams at the next mating.

This year a technology new to St Leger was added to the mix: artificial insemination. Rick AIed 150 four-tooth Romney ewes in a move to give them more links with other flocks.

More linkages are necessary to use the SIL ACE across flock evaluation, and they will also be able to submit ram sires to the central progeny testing programme for bench-marking alongside other breeders.

As for that unfashionable by-product, wool, ram and ewe hogget fleeces are weighed, and fleece quality monitored. "It's still growing, it's still white, I'm still shearing it, and sometimes getting paid for it," Rick says.

Rick now has his eye on the next genomic tool, the Ovine SNP-50 bead chip.

This will be able to pinpoint small genetic differences which together affect a variety of commercially important traits in sheep, including parasite resistance, facial eczema resistance, meat quality and lamb survival.

He says the SNP chip will be able to fast-track genetic gains.

"It will really change sheep-breeding technology in the next 10 years."

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