Scientists in New Zealand say they have bred cows with a genetic mutation which produces low-fat milk.
In what is a world first, the scientists at ViaLactia, an Auckland biotech firm behind the US$109 million research project, have bred the cows, from a single female discovered by researchers when they screened milk from millions of cattle in New Zealand.
The cow "Marge" has a chance mutation which resulted in her milk having a significantly lower fat content than that of other cows.
The scientists say Marge looks like any other Friesian cow, but she has three distinct 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, and she also produces milk with very high levels of omega-three oils which is thought to improve brain power.
The saturated fats found in normal milk are said to be associated with an increased risk of heart disease.
The discovery is so commercially sensitive that the herd's location has apparently been kept a secret.
The scientists had to initially work out how to ensure Marge's calves inherited her genes and also how to generate daughters that would then carry a calf and deliver the same quality milk.
They say the 'eureka moment' came when it was found her daughters produced milk like their mother's.
It seems butter from Marge's cows has the added advantage of being spreadable straight from the fridge, rather like margarine.
The scientists are currently trying to build up a herd and say any products will not be ready to take to the international market for another five to 10 years; they are hoping that Marge's male offspring also carry the same gene.
A summary of the company's research is published this week in the journal Chemistry and Industry, issued by the Society of Chemical Industry and a formal research paper for peer-review is expected to follow.