Holly is ok, but obviously cause of the prickles it tends to not be their favourite thing to eat. My OH found an article about a man with a commercial herd of goats which he fed Xmas trees to, but generally evergreens aren't terribly good for goats. I didn't give our tree to them, and I don't think I would.
Leylandi, we had a fair amount of that, and goats would often snatch a quick mouthful in passing and they never came to any harm, but I would try and steer them clear. There again, ours used to steal mouthfuls of the snowberry hedge, and it is definitely poisonous, and that never did them any harm either.
Beth