Maybe having just bitches with a strong learnt/guided protective instinct towards more fragile charges like here Peepers chihuahuas works for others too, even single males.... But I don't think livestock guardians are really cut out for such, either sex. Just my own instincts here. Some seem to have a rather active and selective prey drive towards most game fowl or other little flighty things like rabbits for example. I suppose it's all in the selection of the individuals and the specific work they've been prepared for as youngsters. Quite honestly I guess most livestock guardian breeds would try and chase and nip even sheep unless guided and taught otherwise, even pups from pure proven guardian stock. Chihuahuas could be at risk though as they could get trampled just in the course of play. That would worry me to distraction where my own anecdotal evidence doesn't allow me to worry so much with JRTs, my own dogs of course.

I guess livestock guardian types are "made as much as they are born" to excel and neither should ever be taken for granted but bitches used for breeding do have to make good mothers. So there is that.

I've noticed there is also quite marked sexual dimorphism in many purely livestock guardian breed types, the bitches being much smaller and more femine and as such are probably not completely able even as a team to work many predators, wolf for example. Not as much as males are.

I know very masculine Boerboel bitches, the breed is not particularly good nor bred for pure livestock guardian work anyway but these masculine bitches do make terrible mothers and will often only throw a single or couple of pups at most. They make excellent homestead guardians though. Most certainly they do, same as males. 

It is interesting this topic because males depending on the type should get on, form a workable pack order (not that it is never unchanging) and live with it to be effective as livestock gaurdians. They're generally worked in teams against certain predators, wolves for example which is what most were used against. Not as individuals. Though some Western selected types that have become breeds outside of the types homeland like "Anatolian Shepherds" are worked as individuals guarding sheep against smaller animals like jackals, cheetah even leopard........horses for courses.

As much as I like bitches not sure many have actually used bitches with or without dogs for work purposes though and this is probably due to the fact that they could present a total distraction due to nothing but pheromones and that is the last thing a shepherd would want with marauding predators to cope with.

Things are very different in the average backyard though. I think bitches would be altoghether more suitable perhaps. Nothing worse than seeing a fenced off single frustrated male barking its head off day and night. This is a danger to everything including the dog.