Today, as I was walking back from the field, on of the student volunteers (we'll call her Tara) came running up to me and told me that one of the pigs had escaped the sty. The poor girl, being timid and outweighed, was at a loss as to what to do. This turned out to be my dogs long-awaited opportunity to do something useful on the farm.
I instructed Tara to keep the door to the pig pen open to admit the fugitive while keeping the others inside. Once she was in place, I called to my dogs and once I had their attention, I started running after the pig, crying in an exaggerated and excited voice "Get the piggy! Get the Piggy!"
Formosan Black dogs (the breed that makes up most of my mutts' bloodlines) though not bred for herding livestock, WERE bred for chasing wild boar. Admittedly, a farm pig is a poor substitute for a wild boar but they made it work. The thoroughly harassed pig decided that the pig sty IS safer than the outside world after all and ran straight back in.
First problem solved, Tara told me that the recently re-incarcerated pig had been misbehaving all day and she was scared to turn her back on it to clean the sty. Once again, my dogs were put on the job, this time as wardens of the pig sty. When any of the pigs would get too close, I'd once again tell the dogs to "get the piggy" and they would chase it back. Once at an acceptable distance, id give a "leave it" command. Eventually, the pigs all decided to stay in one corner, content to hump each other instead of fucking with the farmhands.
Will all dogs behave like this without training? Of course not. But if you spend enough time with your pooch, you probably know how much control you have over him, how he is likely to respond to certain stimuli and most importantly what his natural inclinations are. I know that my dogs love to chase things. I also know that their ancestors were bred for chasing pigs specifically. Because I've already put a lot of energy into teaching the "leave it" command I know that I can expect them to chase the pigs if allowed, and to return to me when I tell them the pig has had enough. This, in itself makes them excellent sty wardens. Because I'd assumed correctly that, when threatened, the pig would run back to a familiar, safe place, this combination of natural inclination and training made them acceptable livestock herders in this very specific instance. That being said, I certainly wouldn't set them loose on a flock of sheep with very positive expectations.
There are many jobs a dog can do besides watered down boar hunting, even with a small minimum of training. Perhaps you have a dog that can't be threatened or bribed into walking politely on a leash without trying to rip your arm off. He might be good at bikejoring. Maybe he is an accomplished digger. Set him loose in the garden on the off season to clear out the gophers and voles. Perhaps he is the laziest dog on the block but the local predators haven't figured that out. Put him in the chicken pen where so long as he is un-inclined to chase the poultry he will likely intimidate predators.
In short, figure out what your dog is inclined to do, give him whatever requisite training is needed to make him successful, then let him loose to accomplish his life goal: to assist and please you. Both you and Mans Best Friend will be glad you did.