A New Zealand biotech company has identified a pretty special mutation in a Friesian cow called Marge. Marge
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.
The trait is heritable, and a commercial herd producing milk that is healthier and butter that is spreadable right out of the fridge is expected to be ready by 2011. The boffins at ViaLactia are looking for the gene involved.