The typical image of a modern biological research lab involves high-tech machinery and table-sized microscopes; at most, there might be some dishes of cells or a few mice floating around. For people with those images in mind, yesterday's odd report on how federal inspectors were surprised to find 841 goats at a California biotech facility they didn't even know existed might come as a surprise. Why, you might wonder, would Santa Cruz Biotechnology need a secret herd of goats at all?

As it turns out, goats (along with rabbits and a handful of other animals) play a key role in modern bioscience—but on the supply side, not the research side. A paper found in a major science journal might well have depended on a goat in some way; it's just that the lab never saw the animal. Instead, the goat probably lived at a facility like the one that's under investigation, while the research lab received the goat's contribution via a UPS shipment.

The men who stare at goats

So what does a goat (or a bunny) offer a biologist? Antibodies. Antibodies are useful for several procedures conducted by biologists because they can stick so specifically to a single target. If you can raise antibodies against a specific protein, you can then use those antibodies to purify that protein out of the huge mix of proteins produced by a cell. If you can generate antibodies to a protein that's on the surface of a cell, you can use them to purify whole cells out of a mixed population.

Antibodies can also be tagged with fluorescent molecules so that they light up all the locations within a cell where the protein normally resides. The result is images like the one below.

Now, you can generate antibodies using many different animals. All you need to do in many cases is inject the protein you're interested in—or even just a fragment of it—into the target animal; its immune system will do the rest. One convenient option is mice, since many research institutions have experience working with them, but mice have a short lifespan and a small blood supply, meaning you don't get much antibody out of them. (There are ways to create cells that provide a permanent supply of mouse antibodies, but they're technically challenging and have a few drawbacks.) If your mouse dies and you still need more antibody, your only option is to inject the protein into a new mouse and start over again, though with no guarantee that any of the new antibodies will have an equivalent quality to the old ones.

Researchers have instead turned to some larger and longer-lived species. Chickens can work well, since they pump lots of antibodies into their eggs, and they produce a lot of eggs. Rabbits live longer than mice, and it's possible to take larger blood samples from them. But goats are better still in both regards.

Euthanizing the factory

Even with goats, however, all good things must come to an end, and that's a problem for Santa Cruz Biotechnology. The company earns its money by providing a huge range of antibodies for all sorts of proteins, some of which are only going to be of interest only to a few dozen labs on the entire planet. For the company, the death of a goat can mean the end of a product.

And Santa Cruz isn't always given the chance to decide when the goats die. Research animals are covered by the Animal Welfare Act, enforced by the US Department of Agriculture. Its rules mean that, among other things, an animal suffering from problems that leave it in pain should be euthanized. But USDA inspectors have, in the past, found problems with Santa Cruz's compliance—including one goat with a large tumor that was kept alive to get more antibody out of it.

This doesn't mean that the recently discovered collection of 841 goats was intentionally hidden; the company told Nature that it had properly disclosed all goats, including the "secret" herd. But the USDA says it knew nothing about the goats and that the existence of the facility in question was directly denied by company officials, despite having been in use for over two years. Several of the goats found at the newly discovered facility were in poor health (though it's not clear any of them were at the point where regulations would require euthanasia).

Still, if you thought that there was no possible reason for a company to hide goats, Santa Cruz actually has one. Whether it did so or not will be determined by investigators.