They may look like ordinary goats but for their creators they are drug-making machines. A herd has been genetically engineered in the US to make a human protein in their milk that can prevent dangerous blood clots.

The goats produce a protein called antithrombin, which prevents blood clotting. One in 5,000 people is at risk of developing blood clots in their veins. Such clots can be extremely painful, even lethal, especially if they break loose and travel through the bloodstream to the lungs or the brain.

Experts say that in practice the medicine, produced by the miraculous animals, fights strokes, pulmonary embolisms and other life-threatening conditions.

The whole process of production needs to be approved by the American Food and Drug Administration (FDA), but it’s clear that medicine is now entering a new era. On Friday, the FDA panel voted overwhelmingly that the process is safe and effective. So when and if the final decision is made, the first ever drug from a genetically engineered animal may start to be produced in the US.

Obviously it's cheaper to create the animals than to build and maintain expensive bioreactors. The technique could make it cost-effective for companies to develop drugs to treat diseases that affect relatively few patients.

Meanwhile, there have recently been misgivings in the US about eating food from genetically modified animals, and some vocal critics of such technology say the wariness could extend to medicines. However, geneticists and animal scientists insist the technology is harmless.