If I recall, the horse noises for animals are unfortunately hardcoded.
If you have a hard time finding game, leave, let the herd move a bit, then hunt again. Sometimes the whole herd will appear at once, so if you're on horseback with a spear, you could kill them all. I hardly ever do that, though, because I'm worried about overhunting. Sure, herds seem to randomly generate, especially around Goutodin and Alt Clut, but whereas in the early game it's not uncommon to find twenty or so deer in a herd, later on, you'll be lucky to find ten or more.