Milk resembling human breast milk has been produced by genetically engineered cows.
Chinese researchers announced in the journal PLoS ONE this week that they had engineered cows to secrete milk containing lysozyme, a protein found in human breastmilk that boosts the immunity of breastfed babies.
The researchers from the China Agricultural University and GeneProtein Biotechnology Company, both in Beijing, say alternatives to breastmilk are important because mothers are sometimes reluctant or unable to breastfeed.
"Modified bovine milk is a possible substitute for human milk," they wrote.
The researchers inserted human lysozyme genes into the nuclei of cells in the bodies of cows, and then used a technique called somatic cell nuclear transfer (the 'Dolly method') to clone the cows.
Uncertain public support
New Zealand researcher Goetz Laible of AgResearch has been involved with boosting nutrient levels in milk through transgenic cows.
He said the Chinese research builds on previous research in the U.S., which developed transgenic goats that produced milk with human lysozyme.
"I think it's great that the step has been taken to go from goat as a model into cattle," says Laible. "It might form a new base for an improved infant formula."
But he says, uncertain public support for the use of transgenic animals in food production means funding for such research has dried up.
"We are not actively working on this for funding reasons," says Laible, who now focuses instead on 'biopharming', the use of transgenic animals to produce therapeutic products, such as monoclonal antibodies.
Technical hurdles and ethics
David Nation from the Dairy Futures CRC in Melbourne says there is no active research on genetically modified cows in Australia.
"The dairy industry [in Australia] made a very definite decision to discontinue investment in transgenics because there are still lots of technical limitations and still large ethical issues to resolve with the community," he said.
The Chinese researchers implanted 312 blastocysts into cows. But only 37 full-term calves were born, of which many did not survive and only four were found to reach normal lactation.
Nation says previous research on transgenic cows in Australia found similar problems with calf mortality.
"That's considered one of the big unknowns in this technology," he said.
"Why is it in the cloning process that there is a significant number of abnormalities that lead to both abortions and low survival for those animals that do reach term?"
Nation said the problems are even more pronounced when the clone has been genetically modified.
Breast milk experts are also dubious about this direction of research.
"This is an interesting scientific achievement but it really has little relevance to feeding babies," said Peter Hartmann, a professor at the University of Western Australia.
He said lysozyme is only one of 279 proteins in human milk that provide protection to babies.
Babies are also protected by antibodies circulating in the breastfeeding mother, said Hartmann, who is president of the International Society for Research in Human Milk and Lactation.
"Breastfeeding is not just pouring breastmilk down the baby's throat. It involves a very complex interaction between mother and infant," he says.
"Claims of producing cows that secrete breastmilk are naïve to the extreme," he said, adding lysozyme would be largely destroyed during pasteurisation of cow's milk.
Meanwhile, Kate Mortenson of Australian Breastfeeding Australia argues there is no need to produce alternatives to breast milk given the existence of breast milk banks.
"The ones in Melbourne and in Western Australia are mainly for premature infants whose mothers do sometimes have trouble producing enough milk to start with. And they have more than enough donors," said Mortenson.
GM Salmon precedent
As for Laible, he would like to continue research on milk from transgenic cows, and is watching with interest to see if US regulatory authorities approve genetically modified salmon for human consumption.
"I think the outcome of that will of course be important for how this whole field is going," he said.
The U.S. Food and Drug Administration (FDA) is currently considering whether Atlantic salmon engineered to grow faster than normal is safe to eat.
Consumer and environmental groups have expressed concern about the potential health and ecological effects of the fish. They claim there is a lack of expertise in food allergies, endocrinology and fish ecology among the expert panel advising the FDA.