Scientists have bred cows that produce skimmed milk and hope to establish herds of the cattle to meet the demands of health-conscious consumers.

The milk is also high in omega3 oils, claimed to improve brain power, and contains polyunsaturated fat. The saturated fats found in normal milk are linked to increased risk of heart disease. The cows, which have a particular genetic mutation, were bred from a single female discovered by researchers when they screened milk from millions of cattle in New Zealand.

Butter from these cows has the extra advantage of being spreadable straight from the fridge, like margarine.

Scientists at ViaLactia, the biotech firm behind the research, have named the cow Marge. Russell Snell, ViaLactia’s chief scientist, said: “Marge looks like an ordinary Friesian cow but has three key differences. She produces a normal level of protein in her milk but substantially less fat, and the fat she does produce has much more unsaturated fat. She also produces milk with very high levels of omega3 oils.”

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Marge was discovered in 2001 when ViaLactia’s researchers bought her from her owner and moved her to a secret location.

The key issue was whether her calves would inherit her traits. “You have to generate daughters and then they have to carry a calf and deliver milk,” said Snell. “The eureka moment was when we found her daughters produced milk like their mother.”

The Auckland-based company says the first commercial herds for spreadable butter could be expected by 2011.

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