Nearly all primitive societies have used slaves for labor at one time or another. Xeno Slavery has little in common with such ancient practices
Xeno Slavery understands that the slave is merely a piece of biological machinery. It has no soul. It has no rights. It is not a sentient being.
Xeno Slavery is a science. It is a collection of techniques that take a thinking creature and converts it into a biological machine. Techniques such as gene therapy, chemical enhancement, and mental conditioning help us turn what were once "people" into things. Things that will work tirelessly and without complaint until they cease to function.