Independent sheep specialist Dr John Vipond says feeding protected forms of soya at 50g/day for every lamb carried and straight soya at 100g/lamb can result in a saving at current prices of more than £3 a ewe.

"High quality silage when supplemented with soya can allow a 75 per cent reduction in concentrate use," he said.

"Soya is the cheapest and best source of digestible undegraded protein in the UK."

"We have been feeding sheep in the same model as we feed cattle, meeting energy requirements and topping up with protein, but the nutritional needs of modern sheep are very different to the animal that this feeding advice was first based on," he said. 

"We used to get pregnancy toxaemia in hill ewes because they were short of glucose; we are now seeing this in lowland-lambing flocks because we are overfeeding energy and underfeeding protein," he added.

He recommends allocating ewes ad lib silage and 50g/day/lamb carried of protected soya during the last three weeks of pregnancy.

Soya only need be fed to multiple-bearing ewes; the nutrition in silage is adequate for those carrying single lambs.

He warned that modern bales are too dense to be fed in ring feeders. "Bales should be shaken out or put through a chopper where possible."