It's estimated that around 8% of rams exhibit exclusively homosexual behavior.
To ensure that the sheep that are being taken in are actually homosexual, they'll place the rams that are assumed to be gay in an enclosure with ewes during the breed's “horny season.” If the ram refuses to mate, he says, “there is a clear indication that he's not interested.”
“So then we put him into our herd, and then a lot of action happens, if you know what I mean,” he says. “It's happening really within minutes.”
https://people.com/farmer-behind-rainbow-wool-tends-only-to-gay-sheep-saving-queer-lives-exclusive-12000672