Cargo 747 pilot here! I’ve flown horses a few times and yes, we have extra crew on board to take care of the horses. The handlers ride in some extra seats we have on the upper deck and check in on the animals every couple hours to make sure they have food and water. I’ve been told that most of the time the horses are fairly well trained and are calm during the flights but every once in a while they get unhappy and bite the handlers. I haven’t had any incidents on my flights that I’ve carried them though.