A breed of goats known as Fainting Goats suffer from "fainting" spells where they just
suddenly fall over and lie motionless. While the action is a result of
panic, it is not actually fainting since the animal does not lose
consciousness. Instead the goat's muscles freeze up suddenly, causing it
to keel over.
What is really happening is a hereditary, genetic disorder that affects the muscles called myotonia congenita. The disease can occur in many different species, including humans. In young goats the condition causes them to suddenly stiffen up and fall over for a few seconds. Older goats seem to have figured this out and will spread their stance for better support or lean against something. The condition is apparently painless and a bit embarrassing.
The goats are still being studied to understand the condition and why it occurs.