Genes for higher protein milk

Israeli scientists have discovered a gene that determines the concentration of protein found in cow's milk, and plan to use that finding to spur the production of higher-protein milk in dairy herds all over the world.

A team, headed by Dr Micha Ron of the Volcani Research Institute, found that a cattle gene called ABCG2 is responsible for the amount of protein found in milk, and that one version of that gene boosts protein concentration by 10%.

The researchers first discovered the mutation in two Israeli Holstein bulls, one of them named Goliath. The study, published in the scientific journal Genome Research, was conducted in collaboration with scientists from the University of Illinois.

It marks the first time a gene responsible for protein content in cow milk has been found - and only the second discovery of a gene linked to cow milk production. (The first, identified recently by a German-Belgian team, affects the fat content of milk.)

Israeli cows rank #1 in the world in terms of average milk production, as well as the protein and fat content of their milk - achievements that are due largely to the science-based approach that underlies dairy farming in Israel.

In that respect, the discovery of the new gene won't make much difference in Israel where dairy cows - all of the Holstein variety - already produce high-protein milk.

Through classical breeding techniques, protein content of milk (or any other trait) can be increased at an optimum rate of 1% a year - meaning it would take at least a decade to augment it by 10%. Now farmers will be able to select a bull that bears the gene variant, and use him to impregnate [through artificial insemination] thousands of cows. A simple blood test can then determine which of the new-born offspring have the high-protein version of the gene, enabling farmers to pick out the 'stars' - for both milk production and siring.

It is a short cut, particularly for developing countries, which will enable them to boost the genetic profile of herds and enrich the nutritional value of milk.

While the average cow produces milk containing 3% protein, those with the mutation produce 3.3% - a significant difference when dealing with thousands of litres of milk per cow per year.

The finding will also have implications for cheese-makers, who require mainly protein.

Even without the benefit of this latest research, Israeli dairy cows are the most productive in the world, averaging 11,600 kg of milk per cow per year, compared to approximately 8525 kg achieved by the American runners-up, 7700 by Canadian cows, 6260 by European Union ones, and 4625 by Australian cattle.