Maximising productivity – a vet’s view

Sandra Taylor

Feeding sheep is the answer to maximising the kilogram of lamb weaned per kilogram of ewe mated.

Veterinarian Pete Anderson says the drivers of this are lambing percentage and lamb weaning weight. The drivers of these are lambing percentage which is made up of scanning and total lamb losses.

Lamb weaning weights are determined by the age at weaning, lamb birthweight and lamb growth rates.

Anderson, who is the Marlborough-based Stockcare consultant, told a recent Beef+Lamb NZ Farming for Profit seminar these are the best ways to measure a ewe flocks’ performance.

He says it all comes to feeding the ewe.

Comparing extensive and intensive triplet systems-based on Stockcare numbers, he says the average lamb mortality in extensive systems is 35%, with the average survival to sale is 195%. Ewe mortality averages 4%.

In intensive systems (indoor lambing, hand-rearing, mothering-on, specialist triplet farms) lamb mortality rates average 23% and survival to sale is 230% with 5% ewe losses.

Another advantage of an intensive system is that it frees up feed for other lambing mobs.

Talking about the impact of mob size and stocking rate on lamb survival, Pete says the fewer the ewes in an area the better the lamb survival. Terrain has a lot to do with lamb survival as often ewes will all pick the same spot to lamb in, creating potential mis-mothering issues.

On hill country farms he recommends lambing the singles intensively on the flats and spreading the multiple-bearing ewes on the hill for lambing.

Triplet loss: mis-mothering is a significant cause of triplet lamb losses and this can occur several days after the lambs appeared to have been successfully mothered up.

Dystocia: Unless the mobs are being shepherded there is little anyone do to stop losses from dystocia.

Lighter lambs: Light lambs produce less heat and have greater heat loss. They have less energy for thermogenesis and don’t survive as well as heavier lambs.

Ewe condition

At set-stocking it is absolutely critical that ewes are at a Body Condition Score of 3.

Less that this and multiple lamb survival goes down significantly.

Every .5BCS lost between scanning and lambing and lambing survival fall 5% and lamb weaning weight falls by 6%.

Lambs from ewes with a lower BCS

  • Have poor vigour
  • Take longer to stand
  • Ewes are less interested in their lambs
  • Ewes have poor udder development.

Unlike cows, a ewe’s milking ability is developed well before lambing.

If ewes have a sub-optimal condition score at scanning, farmers only have three weeks to get condition back on them, so it is important these ewes are identified at scanning.

The issue of bearings

With one or two exceptions, farmers at the seminar reported that bearings were not much of an issue and this was backed up by Anderson.

While visually very evident, the incidence in most flocks is typically between 1% and 2%.

Bearings are a space and pressure issue caused by a relaxed vulva and vagina. It occurs when animals go between famine and feast – being pushed for feed over winter then suddenly put on high pasture covers at lambing. Consistent feeding right through the year will help prevent the issue.

Terrain doesn’t help, when sheep sit uphill after grazing, pressure from the bladder can also contribute to bearings.

Significant weight increase in the first half of pregnancy is an over-riding factor and this can be due to multiple lambs, extra abdominal fat and large lambs.

Therefore, bearing issues are often pre-determined in early pregnancy.

If ewes are well-fed throughout the year they will have a normal-sized placenta, whereas ewes that put on a lot of weight in the first half of pregnancy have a large placenta.

The whole aim is to maintain a BCS 3 throughout the year.

Pete says they can lose a bit of condition between lambing and tailing – but cannot lose condition at any other time of the year.

He doesn’t agree with the idea of taking weight off the ewes after ram removal.

Hogget management has a huge impact on the incidence of bearings. Well-grown hoggets will have fewer bearing problems because they have adequate pelvic space.

Other contributing factors include feeding swedes close to lambing and breed.

Vitamin D may help strength the pelvic floor and this can have an influence on bearings.