Prime time to get ewes back into shape

13 Oct, 2012 01:00 AM

VICTORIAN sheep consultant Jason Trompf is urging farmers to assess the condition score of their ewes at weaning and be proactive in improving it before joining as a starting point for weaning more lambs.

Speaking at the final AWI WoolClip event last week, held in Burra, South Australia, Dr Trompf said the better the condition of a ewe at mating, the more lambs that would be born.

Research in Merinos had shown at least 20 more lambs could be born per condition score – at CS2, about 100 lambs were born but at CS3, about 120 were born.

Dr Trompf said the next step was to pregnancy scan ewes and separate them based on their nutritional requirements.

But only 15 per cent of the Australian sheep flock was scanned for multiples.

“Farmers to get those ewes in the right condition at joining will need to be more proactive in their

nutritional management and paddock allocation and maybe start supplementary feeding earlier than in some years,” he said.

“If ewes are still running in age groups, then you are missing a huge opportunity. They need to be run based on their nutrition requirements, pregnancy status and fats and thins.”

He encouraged growers to ask the question, ‘what is the wastage’ in their own flocks.

Twin mortality reasons included 59 per cent lost to starvation and mismothering – through birthweights that were too low - 17pc died of dystocia, or birthweights too high, and 4pc to primary predation, such as foxes, and 6pc to exposure.

“It’s not until you get twin survival rate up to 70-80pc or above that you enable reproduction rates to rise and subsequently profitability increases,” he said.

“The issue is that if you want to improve reproduction rates you can’t do that with a mindset of get them to have one good lamb. It’s converting the twins we are already conceiving to a live lamb in the flock.”

He said the worst managed farm might have a single lamb survival rate of 75pc and a twin survival rate of less than 50pc while the best managed farm might be up to 98pc and 85-90pc respectively.

Dr Trompf also warned growers to be careful in what they were classing out of their flock.

He said there could be about a 20pc difference in body size between single and twin lambs at weaning at 12-14 weeks.

In the same flock, the single lamb of a maiden dam might be 29kg at weaning, but twin lambs would only be about 25kg. An adult dam in the same flock might wean a single lamb at about 32kg but a twin might be only 27kg.

“Classing them as one mob, the smaller animals will be at the end of the line and you’re culling all the twinners from your flock. It is recommended to present single-born and twin-born ewe hoggets to the classer separately,” he said.

“Even as these sheep mature, much of this difference remains to hogget age and beyond. It’s not until full maturity that the difference between singles and twins reduces to about 5pc.”

Weaning percentage, scanning rate and lamb growth rate all combined to drive kilograms of lambs weaned a hectare. But Australia’s lamb marking rate had averaged about 80pc since 1990 across sheep enterprises (see table 1).

“The challenge for our national flock is that 80pc of lambs marked to ewes joined is barely self-replacing. So the moment you want to grow your flock, you have to sell less in order to do so, which will adversely affect cashflow,” Dr Trompf said.

“Despite this, we’ve had about six million ewes on properties where managers have gone through the Lifetime Ewe Management program, and as a result they have significantly improved their lamb and ewe survival so now they are weaning an extra 20pc of lambs per hectare on their farms.

“The challenge for the national flock is to encourage more involvement in the program as well as increasing commercial adoption of ultrasound pregnancy scanning for twins.”




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