Researchers in New Zealand have genetically engineered a cow to produce milk with very little of a protein that causes an allergic reaction in some children.
They hope the technique, which uses a process called RNA interference that reduces the activity of certain genes without eliminating it completely, can be used to control other traits in livestock.
With new mothers breastfeeding less, cows' milk is an increasing source of protein for babies, but the different composition of cows' milk can cause an allergic reaction.
In developed countries, 2% to 3% of infants are allergic to cows' milk proteins in the first year of life, the researchers said in a paper published in the Proceedings of the National Academy of Sciences.
Protein reduced by 96%
Anower Jabed and colleagues at the New Zealand government-run AgResearch company said their genetically modified cow produced milk with a 96% reduction in beta-lactoglobulin (BLG), a protein known to cause allergic reactions that is not present in human milk.
While there are dairy industry processes that can reduce the allergenic potential of normal milk, they are expensive and can result in a bitter taste.
Another gene manipulation technique using a process called homologous recombination could theoretically knock out, rather than suppress, the gene that produces BLG but the researchers said that, so far, this has not worked.
Bruce Whitelaw, professor of animal biotechnology at the University of Edinburgh, said the New Zealand research "offers a good example of how these technologies can be used to provide alternative strategies to current manufacturing process".
He said that although RNA interference has been shown to work in manipulating plants and worms, "it has not worked in livestock before".
Whitelaw told Reuters that aside from accentuating or reducing genetically determined characteristics in farm animals, such as growth rate, the technique could be used to improve defence against infection.
"Time will tell how widely applicable RNA interference will be in GM livestock. But this is certainly a milestone study in this field," he said.
(Reuters Health, October 2012)