Sheep Scanning

Pregnancy diagnosis of sheep.

By March most sheep farmers will have vaccinated their young stock with Toxovax and Campyvax 4. The mineral status would be measured and supplemented where necessary particularly Selenium and Iodine. Ewes will be putting on weight and teasers introduced two weeks before the rams go out. Feed budgeting will ensure weight gain continues for the first few weeks of mating. The rams would also have been checked to ensure that they are fertile and supplemented with the same minerals as the ewes. Lameness problems will have been attended to. They will NOT be vaccinated with Toxovax!

So the next step is to scan the ewes to see how successful you’ve been. This is done 80-90 days after the ram is introduced to the ewes. This date is a compromise to get the most information out of a single scanning episode. It allows accurate detection of multiple lambs as well as dry ewes. Variation of this date reduces the accuracy. Scanning at, for example, 100 days after ram introduction will give greater confidence that dry ewes are in fact dry as scanning can only detect pregnancies at 35 or more days! But because fetuses are large at 100 or more days it is more difficult and hence less accurate in detecting multiple births. The reverse is true scanning at 70 days after ram introduction.

If rams are removed after 3 cycles (51 days) then at 85 days dry ewes can be accurately detected. If rams are left in longer then some ewes called dry may be pregnant but very late lambers. They could be rescanned one month later but most people find it more economic to send them to the works.

The benefits of scanning include:

1. Early detection of dry ewes which can be culled at a premium price and saving feed for pregnant stock.
2. Determination of ewes carrying single, twin or triplet lambs.

Ewes can be grazed according to their requirements reducing Dystocia (trouble giving birth) in singles and Sleepy Sickness in twins. Ewes can be put into lambing paddocks which suit them. Twin lambs are born heavier which improves their survival rate. On better feed the lambs’ growth rate is better. Twin bearing ewes will hence be in better condition at weaning and more likely to produce twins the following year.

1. Replacements can be selected from twin lambs.

To put a dollar value on the benefit of scanning is difficult. If your tailing percentage is in the region of 80-90% then the bulk of the ewes will be carrying singles and if it is above 160% they will all have multiples. You may choose to scan in either of these situations just to remove the dries.

The greatest benefit occurs when you tail in the region of 120%. Generally if your scanning results have been about 150%; which means about half your ewes are having singles and half are having twins, with a dry rate of 3-5%. The financial benefit assuming a premium on dry ewes sent to slaughter early, greater survivability of lambs and improved ewe survival (Dystocia, Sleepy sickness) and ewe weights at weaning is in the order of $5 - $7.00 per ewe scanned. This is a great cost; benefit ratio and probably explains why virtually without exception everybody who tries scanning continues to do so year after year.

For more information or to book your ewes in for scanning, please contact us.