I currently have a three year old rough collie raised from three weeks. never a mean look towards domestics.
a fifteen year old german shepherd, when got August of this year, was recent and through whole life a killer of one colt, cats, chickens, guinea, geese, and ducks. took two days at most to deter her from looking hard at stock. she even played nanny dog and protected young ducks that hatched soon after got her. so cute how the dozen would run and huddle under her when hawks around.
An Australian cattle dog/red heeler that just got almost two weeks ago now, about four months, wild and attacked anything that moved or made noise first day, took two days to deter. She sounded alarm already and got flock rouned to pond, went and bayed a "panther" (jaguarundy), and al three then chased and attacked all way till couldn't hear panther screaming no more (we live in wild mountainous country).
Locals talk about how natural great pyraneese dogs around here are, but when not trained and maybe needing be contained they just roam and destroy and kill eat stock worse than others cause of size ect. I've retraind some that then were decent guard dogs but slow lazy and not economical to keep for anything but huge farms by today's standards of most. many I've heard of and seen kill stock raised even with, or bought proven loving stock protection for flock of previous owner.
I've done years of dangerous (meaning strong and usually large, but usully less aggressive than media and politicians make out for campaign scares for votes of those choosing to only believe everything they hear), breed, fighting dog/attack dog/private security dog/police dog/military dog, and hybrid work. never found a breed generally that couldn't be easily quickly retrained, bssides retrivers (not bright and too mouthy) and chows (most headstrong loyal to one original owner only, and very game all around dog I've worked with), for some reason.. lol
i just take the dog calmly along and back and fourth, slip lead at top of neck if needed or loose if not, and correct with sharp subtle sound and sharp subtle jerk of lead releasing immediately repeating as needed (never choking or holding pressure, as that then fixates the dog more on), when dog shows interest at first at all till it gives up and stops tensing trying to face, look at at all, perk ears to sounds of, or lip licking ect. when dog stops sit or lays relaxed looking away or at you then the first step is started. it helps greatly if prey ect animal isn't terrified/reactive at all, but once its been attacked and drawn blood from/injured, that can be difficult. lol
Any dog needs to know your boss and its not. i practice "take it" and "leave it" with new dogs first thing, it then gets to know house rules right off that everything is mine and as such learns to obey what when to do and not to do. toys bones food, everything is given taken given again and maybe ends up taken at end depending on how well exercise went.
if i put a baby chick in a pitts mouth from two hours to two days after starting, it won't hhurt it. its a dog, its vred and hard wired to work as programmed, and you just need to look at from third party, but then friends say a lot easier for me because i was trained to handle K-9 police and military units, and wolves and hybridizations (different job), which leaves little room for error or your dead or hurt bad.. dogs taught to how and when to attack or defend owners stock land ect are less likely to go off on someone/they shouldn't, and do less damage IF do, but can inflict fatal damage by accident if training done badly, harshly, or no to lazy and not assertive enough training is done.
Staffordshire bull terriers and jack russel terrier, those two most common trainable and effective of terrier breeds, but over all shepherds and collies (old word coined for shepherd types meaning "useful"), top list. Rotts oldest of guarding and herding breeds (most told "old breeds" are recreations of lost breeds), are great but actually lack greater mobility ect due to breeding recent for thinner tails docked that decreases their mobility. Olden times some working type dogs had tails cut off or "docked" so they weren't able to chase as effectively chaseand use to run down the lords of lands wild game animals. taxes were higher and fines for those poor commoners that had dogs to work that may hunt or let dogs hunt game. (Then useless show type owners allowed then showed and started favor and "standard for "docked" look).