Researchers in New Zealand genetically engineered a cow that can produce hypoallergenic milk. The calf’s milk lacks milk protein beta-lactoglobulin or BGL, which is what causes allergic reactions in humans and what’s missing from human milk.

So how do you go about making a hypoallergenic dairy cow? They used RNA interference in a female cow’s egg cell nucleus to turn off the gene that signals for production of BGL. Then they fertilized the egg and artificially inseminated another female cow.

It took 57 attempts to produce the calf. After the healthy baby was born, researchers gave the calf hormones to make it produce milk early, and lo and behold, no BGL.

But there’s another strange trait the cow expresses: It has no tail. Researchers aren’t sure if the calf’s vacant backside is because of the RNA interference or some unplanned genetic mix-up.

Photo: dcysurfer / Dave Young/Flickr