Ewe condition critical for flock productivity

At the Merino Sire Evaluation Field Day at Lameroo recently, the University of Adelaide's Forbes Brien presented the latest trial results that looked into "retaining performers".

Associate Professor Brien said it was important for producers to use better ewe management, after "alarming figures" about the national ewe flock were released.

"It is getting harder to produce enough lambs for slaughter - the ewe flock needs to be increased," he said.

Trials were held in NSW at Armidale and Trangie, and at Turretfield near Roseworthy to see if more lambs could be weaned by culling 'passengers' and keeping 'performers' for longer.

Associate Prof Brien said to increase reproduction rates, the ewe flock needed to be in the best condition possible.

"In earlier research, we found that single-bearing ewes in a condition score of just more than two at lambing had a lamb survival of 85 per cent, but with a condition score of three or more, it was 91pc," he said.

"The clear message here was that producers need to get the basic nutrition of the ewe flock as good as it can be by culling and selection."

Associate Prof Brien said this led to a study of the overall performance of dry ewes, which found ewes that were twice-dry at two to three years old would record about 50pc fertility across their lifetime.

"But if ewes had weaned twice, it was 91pc for lambs weaned," he said.

"So, culling ewes is not new, but retaining performers is. Essentially, we cull twice-dry ewes - but we retain the best performing ewes one to two years longer."

Associate Prof Brien said rather than culling an entire 5.5-year-old to 6-year-old age group based purely on age, it was preferable to retain the better half of the older ewes.

He said replacing older but potentially more reproductive ewes with maiden ewes dropped the performance of the entire flock.

"Unless it is an exceptional ewe, its performance can be 15pc lower," he said.

"In the Turretfield trial, a 4-6pc improvement across the entire flock was achieved by retaining older but performing ewes."

Associate Prof Brien said trials at Turretfield also looked into whether producers could effectively cull ewes based on one reproductive record.

"We removed dry ewes, almost 30 per cent of the flock, and we got about 1.7pc overall improvement in reproduction for the whole flock," he said.

"When we removed twice-drys, we threw out a quarter of 30pc, and had the same increase."

THE SA Merino Sire Evaluation Trial for 2019-20 was held at the McMahon family's McPiggery operation at Lameroo, with trial results discussed at a recent field day.

Eighteen rams, including three link sires, were entered in the 2020 trial.

Sixty ewes were joined to each sire via artificial insemination in late November 2019 and at day 50, the ewes were pregnancy scanned, resulting in a 72 per cent conception rate.

Prior to lambing, ewes were separated into six twin-bearing mobs and three single mobs, with lambing in late April.

Lamb marking was in mid-May, with visual traits of fibre pigmentation, non-fibre pigmentation, recessive black, black spot, breech cover, and breech wrinkle recorded.

The sire pedigree was determined by DNA testing and there were 877 progeny from the 18 rams.

The average marking breech cover was visually assessed as 1.0, from a 1-5 range on the Visual Sheep Score ranking, and the average marking breech wrinkle was assessed as 1.5.

These scores indicate that the lambs were reasonably plain and ewes were maintained in condition score three.

Weaning was at 13 weeks, in late July.

Weaning weights were assessed and single lambs weighed an average of 33.3 kilograms, and twin lambs an average of 29.4kg, providing a total average weaning weight of 31.3kg liveweight.

RELATED READING: Sheep producers urged to be 'buyer aware' on OJD risk