WOULD you eat genetically modified cheese? That is the question food companies will be asking now that cows have been engineered to produce high-protein milk for cheese-making.
It is the first time that cows鈥� milk has been altered to produce food rather than pharmaceuticals. Dozens of extra copies of the genes for two milk proteins, beta and kappa-casein, were added to fetal cow cells, which were then cloned. Of 126 embryos implanted, 11 calves survived till weaning. The milk of nine of them contains twice as much kappa-casein as usual and up to a fifth more beta-casein (Nature Biotechnology DOI:10.1038/nbt783).
Dairy cattle breeders have long selected for high levels of casein. Casein-rich milk yields more cheese and clots more quickly. 鈥淏asically, cheese is casein. An increase in casein would be of great value to the dairy industry, because farmers are paid on the basis of how much casein is produced in the milk,鈥� says project leader G枚tz Laible of the Ruakura Research Centre in Hamilton, New Zealand.
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Laible says it is too early to think about commercialisation. If the institute does press ahead, it would take several years to create large herds for commercial production. The attitude of consumers could be crucial. 鈥淚f people don鈥檛 want to eat it, no one will produce it,鈥� says Vanessa Atkinson of Greenpeace Australia. 鈥淲e鈥檝e seen that clearly in Europe.鈥� Milk from cows fed Monsanto鈥檚 GM growth hormone has long been controversial, and is banned in Europe and Canada.
But most cheese is already made using rennet from GM yeast, with little public opposition. And some companies may see the high-casein milk as the ideal product to spearhead the sale of GM animal products.
With farm animals like cows there is little possibility of transgenes spreading to wild populations 鈥� a serious worry with the fast-growing transgenic salmon that AquaBounty of Massachusetts wants to market. And because the cows simply make more of the proteins already found in milk, there should be no risk of allergic reactions as there might be with genes transferred from other species. The cows do contain a gene for resistance to a bacterial antibiotic, but Laible says the associated protein should not be present in the milk.
However, many consumers will not be given a choice. GM plant products do not have to be labelled in the US and Australia, and the same is likely to apply to GM animal products. But such milk would have to be labelled in the European Union.
Another contentious issue is animal welfare. 鈥淲e don鈥檛 think the use of cloned or GM animals in agriculture is justified, on the grounds of animal suffering,鈥� says Sue Mayer of the lobby group GeneWatch in Britain. Half of the calves in New Zealand died between birth and weaning, she points out.