An experimental farm in Russia could soon be producing human breast milk substitutes following successful milking trials on mice, scientists report. Thanks to human genes spliced into their genome, the mice are the first genetically modified animals to produce lactoferrin. This human breast milk protein protects babies from viruses and bacteria while the infants' immune systems are still developing (get a quick genetics overview).

The ultimate aim of the Russian team, and of similar research projects in other countries, is to extract lactoferrin from the milk and use the protein to create healthier baby formula.

"Mouse milk is very protein-rich, and this can also translate into very high concentrations of transgenic protein," Patrick van Berkel, a senior director at the Danish biotech company Genmab, wrote in an email.

Breastfeeding mothers typically produce 4 to 5 grams (0.1 to 0.2 ounces) of lactoferrin per liter (about a quart) of milk.

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