The discovery should make it easier to clone cattle, but comes as French scientists publish the most complete description yet of health problems linked to the cloning process.
Colostrum is rich in white blood cells.
But the Embryo Transplant Institute of Snow Brand Milk Products, on Japan's northern island of Hokkaido, cloned two calves using stray mammary gland cells in the secretion. The new technique will cause less distress and allow researchers to screen larger numbers of cells for cloning. It died of severe anaemia aged seven weeks after its spleen, thymus gland and lymph nodes failed to develop normally.