Scientists at the Government's AgResearch science centre at Ruakura, near Hamilton, say they have produced a herd of nine cloned, transgenic calves whose milk boosted yields of two types of caseins by up to 100 per cent.
The researchers, led by Goetz Laible, said the technique of delivering extra casein, if
taken out of the lab and adopted by the dairy industry, offered "substantial economic gains".
It could be widened, to "tailor" milk for human consumption, they said.
The two key proteins are a boon to dairy manufacturers because they help liquid cheese to solidify and they also drive off whey, a watery by-product that is unwanted in the curdling phase of cheese-making.
AgResearch won permission from the Environmental Risk Management Authority (Erma) in 1999 for two parts of its original project to create up to 90 engineered holstein-friesian cows.
The most controversial part of the research - putting a copy of a human myelin basic protein gene into cattle cells so the beasts would secrete the gene in their milk - was held up in regulatory delays and court battles, but eventually approved.
Then in 1999, the scientists were given the go-ahead for two pieces of important research related to dairy production.
One was to knock out of transgenic cattle the gene that controls beta lactoglobulin, the main whey protein in the milk of cows.
This protein, thought to bind fatty acids for the benefit of animal young, is not found in human milk, and causes allergenic reactions in some infants and adults.
The other was to insert additional copies of two cattle milk casein genes to produce milk with more protein, without reducing the amount of milkfat already produced.
Conventional selective breeding to lift the protein level would be accompanied by a drop in the fat production.
This is important for butter and cheese manufacture.
- NZPA
Herald feature: Genetic Engineering
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