Now, genetically modified cow that provides 'low allergy' milk

The modified cow produced milk lacks beta-lactoglobulin - a major whey protein of cow and sheep's milk, to which some people are allergic.

The study has been dubbed as a "milestone" by scientists. However, some campaign groups say it raises ethical concerns, the 'BBC News' reported.

There are important differences between a woman's breast milk and cows' milk, such as beta-lactoglobulin, which is found in milk from cows but not people.

"It is not surprising that is constitutes a major milk allergen," researchers from the University Waikato in New Zealand said.

The instructions for making the beta-lactoglobulin protein are contained in genes in the cow's DNA.

The scientists added extra genetic material to disrupt the manufacturing process using a technique called RNA interference.

The resulting calf was born without a tail, however, the researchers say that is "unlikely" to be because of the genetic modification.

It has not yet become pregnant and produced milk normally so the scientists used hormones to jump-start milk production.

"All milk samples from the transgenic calf were devoid of any detectable beta-lactoglobulin," they said.

The researchers concluded that the technique was an "efficient tool" for modifying livestock.

The study was published in the journal 'Proceedings of the National Academy of Sciences'.