If these livestock animals are considered wild and a nuisance then have at them with whatever you are legally allowed to use.
There's a lot better ways to handle escaped livestock than shooting at them IMO. Better fences come to mind, yours or the owners. Livestock is usually someones property and unless you live in a free range area its up to the owner to keep them contained. Besides, if you spook a cow, steer or horse they'll take off and run though or over anything that gets in their way and often not in the direction you expect. Just because they're on your land doesn't make them your property and any damage they get or do from being spooked by being shot at will be your legal and financial responsibility.