This fact emerged yesterday as PPL Therapeutics, the Edinburgh company licensed to produce cloned farm animals, announced that it could fulfil the pounds 100m annual world demand for the blood clotting protein Factor IX using only 50 cloned sheep.
Each would have an added human gene so that it generated the clotting protein in its milk. That could then be extracted and sold on the world market.
In the UK alone, Factor IX - a protein essential for causing clotting - is prescribed for approximately 400 people who have the "B" form of haemophilia, the rarer form of the disease in which the blood will not clot. The UK market for Factor IX is about pounds 4m annually, and the world market is 25 times that. Most is presently derived from human plasma.
PPL says that its transgenic sheep produce 300mg per litre of Factor IX in their milk. Alan Colman, the company's research director, said: "I am very excited by this very high-level result. Levels of Factor IX in human blood are very low - approximately 5mg per litre - so the sheep have made 60 times the naturally circulating amount of this high-value protein."
The protein would be pure, so it should be disease-free. By contrast, the Government said last week that all British-derived blood plasma (from which Factor IX is made) would be destroyed, because of fears that it could be contaminated by "new variant" Creutzfeldt-Jakob Disease, caused by eating BSE-infected food.
PPL has licensed the technique that produced Dolly - taking the DNA from an adult and putting it into an egg cell whose nucleus has been removed. The company could quickly produce a flock able to out-produce every rival, feeding it on nothing more complex than grass.