I'm looking to own a cattle farm in the near future, and while I already have a GSD, he's in training to be an SD. As such, I will need to get a dog that can live outside with the cattle and handle being a farm dog before a house dog first and foremost. This is mainly aimed towards knowledgable dog owners of the following breeds and/or knowledge of which breeds seems best regarding the situation.

Great Pyrenees are highly recommended for guard dogs of cattle, and normal don't venture out of the yard so they are more likely to stay with the cattle after chasing whatever foe out of the yard.