I wasn't aiming at a massive set-up like the ones used for chickens, cows, fish, pigs and such. I was referring to a small to medium-sized group of deer bred for food. I should have been more specific. From what I see in the butchers and supermarkets today, the demand for venison isn't particularly high, so I doubt people are going to move to farming deer like they do with many domestic animals.
Pumping the animals with drugs isn't necessary or compulsory either, it's just done (mostly) to improve the growth rate.
Also, regarding fish, bacteria and disease spreads easier in water than on land.
We don't live in a perfect world, I'm aware of that. Not everyone is going to care about the environment and how to farm sensibly, by a long shot. There are too many humans in the world and a lot have lost their ability to care for themselves, thus the amount of poorly-kept animals packed together and spat out by the millions in packets every day.