Shepherds' warning on twin lamb disease

ALTHOUGH the snow is now in slow retreat over most parts of Scotland, the big worry for sheep farmers still lies in the future.

The vet in charge of the Scottish Agricultural College centre at Perth, Graham Baird, yesterday advised shepherds to blood-test their pregnant ewes to confirm whether they were sufficiently well nourished.

The snow that fell over Scotland and which is still falling in some parts of the country caused huge problems for many farmers, who struggled in desperate conditions to feed their stock. Inevitably, the big freeze, the worst weather for almost three decades, disrupted feeding for many animals, putting pregnant ewes under stress.

Even in normal years, ewes carrying twins and triplets often struggle to meet the energy demands of developing lambs, and, as Baird pointed out, this hasn't been a normal year.

When any break in feeding occurs, pregnant ewes are forced to fill the energy gap by using their own fat reserves. This utilisation of fat reserves is exactly the principle on which the Atkins diet works for humans.

However, in pregnant ewes it increases the risk of developing "twin lamb" disease, which occurs when there is a build-up of toxic chemicals in the blood. Fewer than a third of ewes affected make a recovery, and even fewer go on to rear lambs successfully.

Baird said the best way of identifying an energy gap was to run a simple blood test on a selection of ewes in the flock. This test measures a chemical called BOHB, which increases in the blood when ewes are underfed. He advised farmers to carry out these blood samples about a month before lambing. He suggested, for flocks with scanning results, a sample of five ewes carrying twins and five with triplets. For sheep that have not been scanned, shepherds should sample ten animals of average condition.

By carrying out the test at this time in the pregnancy, it would give shepherds time to make any necessary changes to diet. He said farmers finding one or two cases of twin lamb disease each year might be seeing only the "tip of an iceberg". Baird added: "Many other ewes could be suffering from a sub-clinical disease energy gap, which has implications for their ability to rear lambs successfully. It's vital to monitor energy balance in lambing flocks to prevent twin lamb disease."