Gene key to dairy profits

By PHILIPPA STEVENSON

The identification of a cattle gene governing milk yield and its protein and fat content may enable farmers to breed animals that produce high-profit products.

The finding by New Zealand, Belgian and Dutch scientists is the first from an eight-year-old project investigating the function of cattle genes.

Dr Russell Snell, of Fonterra research subsidiary ViaLactia Biosciences, is one of the international team who reported the discovery in a paper published last month on the Genome Research www.genome.org website.

Cattle had one of two versions of the gene, known as DGAT1, he said.

"One version will give you more protein, more milk volume and less fat, and the other version more fat, less protein and less milk volume."

A startling aspect of the discovery was that scientists had previously believed that fat and protein "travelled together", with the greater fat content of some cow's milk matched by greater protein content, he said.

The team reported that because fat and protein had different economic value in some countries, the ability to identify a gene governing the components could have a significant effect on how milk production was modified in response to consumer demand.

Chris Moller, managing director of Fonterra ingredient business NZMP, said the discovery was a win-win for farmers, manufacturers and marketers.

"Overall, a development like this definitely drives in the direction best for the business. Even though there might be more volume of protein, there is a strong demand for it globally. It is worth more and can be used for a lot of functional applications."

Milk with a higher protein content would be valuable because it was always a challenge for the company to sell fat in products such as butter and cheese. They were most wanted in markets such as America to which New Zealand had little access.

NZMP's main markets for fat were the low-returning, politically and economically volatile regions of Eastern Europe and the Middle East.

Protein was worth more in the market, and consequently to farmers.

Snell said the gene variation occurred naturally in cattle. "It's nature's experiment, and we're trying to unravel it."

The aim of the research was to help with breeding decisions. "That's exactly what breeding companies have been doing for years. They've been breeding for a trait, but this adds to the accuracy of the breeding."

A simple DNA test, available from research co-sponsor Livestock Improvement, showed which variation of the gene a cow had.

On average, the "more-fat" version was prevalent in New Zealand herds - an expected result since a higher fat content in milk had been emphasised in dairy cattle breeding here for more than 30 years from the 1950s.

American animals appeared to have the "more-protein" version.

Snell said the incidence of the gene versions varied between breeds. Jersey cows, known for the higher fat content of their milk, tended to have the more-fat version.

The discovery was made in June 2000, with preliminary patenting following that October. Breeding and genotyping companies around the world had since shown interest, Snell said.

Another factor identified in the DGAT1 gene was that the different versions also influenced the softness or melting point of the fat, which had implications for processing and products.

"It really points out what a wonderful thing it is finding an individual gene and how much biology you can unravel once you have it."

Moller said that while butter's taste was popular with consumers, its lack of spreadability was not.

"If we could have a product that spread but still had the taste of butter, there would be huge consumer demand and acceptance for that."

The company had created spreadable butter but at high manufacturing cost.

"To the degree that cows could be bred to produce softer fractions of fat, that would certainly have consumer demand and, presumably, reduce the [manufacturing] cost involved."

Snell first read in a scientific journal about the gene in mice. Researchers investigating human obesity found that when the gene was removed from a mouse it lost the ability to lactate.

He wondered if the same gene might be associated with traits in cattle. Some investigation was done in New Zealand before the project was passed to Professor Michel Georges, head of the genetics depart at the University of Liege's veterinary medicine faculty in Belgium.

Georges' group did more analysis and identified the variation.

"This is how cross-species research is really important," said Snell. "They make things so simple."

The work was financed by ViaLactia and Livestock Improvement Corporation in New Zealand, Dutch and Belgian organisations and the European Union.