<<Lets say that I owned you as a slave , I would put you in the best most healthy circumstance I could . . . >>
That is simply not true. In fact, it's quite absurd. My best and most healthy circumstance would require regular medical attention, at times expensive medication, bed rest when required, regular and stress-free time off, ergonometric tools and dry, insulated cabins with plenty of fresh air and sunshine, kept cool in summer and warm in winter, plus a healthy and nutritious diet.
Assuming that you are sane and reasonable, your concern with me would begin and end at the concept of cost-benefit analysis. At the minimum possible outlay on your part, you need to get a good day's work out of me each and every day. When the cost of meeting my health and other needs approaches the cost of my replacement with another slave in better condition, that is the day I am thrown on the scrap heap. Since I was not paid any wages for my years of labour for you, I have no resources of my own to fall back on. I am now left to sink or swim by a master who doesn't really give a shit if I live or die, any more than he cares what happens to his old sofa or chest of drawers.
Moreover, even as a healthy and productive worker, if I don't feel like taking any more of your shit one day and mouth off at you, or if I should show any visible attraction to one of your womenfolk (or she to me) you can have me flogged or horsewhipped, probably even to death.