When a goat passes out or faints it's because the goat was born with a congenital condition known as myotonia congenita.
The condition the goats are born with is also known as Thomsen's disease. When a goat is born with this condition it causes their muscles to seize up when they've become startled which makes it appear that the goat has fainted or passed out.
This condition can also affect some humans as well.