Goats bred for milk or their janitorial talents may be slaughtered when they're older, which yields meat that can be tough and gamey.

WSJ: Get Your Goat On

The silk gland of spiders and the milk gland of goats are almost identical.

FORBES: Charlotte's Goat

The FDA has approved only one product, ATryn, an anticoagulant derived from the milk of transgenic goats.

FORBES: White House Reverses Itself, Lifts Political Block on FDA Approval of GM Salmon

It's a model that scientists have tried with spider silk before, but because the proteins in spider silk are so large, it takes some pretty wacky-sounding techniques to replicate them (like getting it from the milk of transgenic goats).

BBC: Hagfish slime: The clothing of the future?

These hardworking rural dwellers make their living by herding horses, camels, goats, cattle and sheep for milk, cashmere, meat and other livestock products.

UNESCO: Herder Families Literacy and Life Skills

The settlers worked hard, clearing the forests along the valley floors, and making their living from livestock in a region where few crops grow well, but Alpine meadows are pasture for goats and cattle which produce unrivalled milk and cheese.

BBC: Hiking the Alpine Walserweg trail

He started with mouse embryos and graduated to goats, whose large mammary glands make better milk machines.

FORBES: Charlotte's Goat

To cover the down payment on his tuition, he sold fresh milk and cheese from a herd of goats that he bred.

NEWYORKER: The Visionary

Since transgenic goats, for example, are living factories whose worth depends on their producing as much milk as possible, every measure is taken to keep them happy, healthy, well fed and sequestered from non-transgenic animals.

ECONOMIST: REPORTS

Nexia became known as the spider-silk company, after it created transgenic goats capable of producing spider silk (which is, in fact, a form of protein) in their milk.

ECONOMIST: REPORTS