What causes goats to fall over?

There is a breed of goat called a fainting goat which faints and falls over because of a condition in their brain. It may not be a defect but rather a "play dead" defense mechanism.

There are also fainting cats and rabbits.

There are not very many because it doesn't always work if the attacker is hungry and eats fainted pray. It is natures Second Harvest Food Bank.

It is a genetic abnormality on one type of goat. 

They were eating rotten fruit and became totally inebriated.  Try it yourself.  I bet after enough drinks you will get the same condition.

I guess the lack of a due grip...😉