Even today serious working dogs performing traditional roles like hunting and guarding livestock are treated very harshly. I believe these sub-cultures can essentially serve as windows into the past and give you a good idea of how things used to be. In fact it's almost like the man-dog alliance is a "dumb animal" with predictable behaviours. Just as a leopard doesn't need to study how leopards used to act in 1405 in order to act the same as them, so too with man-dog hunting teams and the like.

One only needs to compare photos and videos of boar hunting with dogs in Australia today in 2020, with old art works of boar hunts from medieval Europe, it's uncanny how perfectly the same it basically is. The dogs are the same, what's going on is the same, down to really peculiar little details like dogs of a certain type wearing armour and dogs of another type not, certain dogs of a specific appearance being lead in and released while others of a specific appearance run free... Now the modern Australian hunters aren't history buffs or art connoisseurs, they're quite frankly entirely uneducated rednecks just doing what works and adapting to the demands of the task, but it ends up uncannily familiar to someone who is a history buff and art connoisseur. You're seeing something medieval when you watch them do what they do today. And yes they are harsh, dogs get badly injured and/or die frequently and they don't really care. I'm confident it's fairly faithful to how things always were.

While you're waiting and if you're interested, /u/sunagainstgold talks about the training of dogs in the medieval Arab world here:

What do Ancient and Medieval sources say about the care and training of dogs?