A great Guardian dog holds their weight, however, they take training. livestock pups are in training it take months and even up to two years old. however, only get one from a farmer and older pups 4 , 5 or more months old that have lived continuously with livestock. Finding a well trained guardian dog is not unheard of but hard, no one will sell a well train guardian dog. Unless that dog is out of a job which happens. We had a sheep farm locally get auctioned off and his dogs he rehomed to individuals with livestock.. SO it happens but if looking for a full grown dog you must watch out for dogs that people made pets and then sell them as guardian dogs..
IMO Guardian dogs are awesome, I have one and i love him, he is still a pup though but he was well trained and 6 months old when i got him..he helps my st bernard who i will say is not a guardian dog, the bark just deters animals to keep away. she will protect my sheep but she not protecting chickens she just tolerates them..in any rate guardian dogs are not really quick fixes because it takes alot of time to train them.
Also farmers train guardian dogs differently ask what they are trained for like my Pyrenees will shoo black birds off and bark overhead at them, he does not like them in the yard, he also cases coons, skunks and other wildlife. However he is trained to kill cats because he came from a farm that had serious issue with outdoor cats preying on their fowls and chickens. I am glad that farmer offered what his pups where trained to because i have a indoor cat and now i have to make extra extra sure she never gets outside.
I think the electric fence is a great idea because I have seen my st bernard chase a coon out of my yard that when up and over my 6ft fence and if a coon can do that i bet a fox can to.If you wish a guardian dog in training, even older guardian pups are great even though they are learning they got the basics and the bark is like a megaphone..large breed pups eat alot, however once they are older they do not consume huge amounts of food. infact they eat less than expected..guardian dogs r good but you need fencing until it is trained well and more than likely after it is trained as some guardians like to roam.
If you have an Amish community around look to them also. I have a friend that has a Pryenees trained by Amish and that dog is amazing.