score:7
No, I don't think that the kind of detailed breeding that a poodle breeder does was ever more than a tiny element of the Slave system in the Americas. Sure, a person wanting to sell slaves for value will look for healthy slaves. But the lifetimes are too long and humans too ornery to ask for much success treating them like lab animals.
Also, marriages were usually encouraged among slaves to both reward well behaved slaves and to support the supposed civilization and Christianization that was one of the supposed reasons African slavery was acceptable. An overly "scientific" breeding program would be viewed poorly by the other slaveowners around. Even normal operations that were too directly visible as breeding for sale were looked down on, although everyone sold off slaves. Often you will hear assertions that that only transplanted Yankees would do that. Again, the vision of slavery as a humanistic and "family like" atmosphere was clung to very strongly, no matter how poorly this image matched the underlying reality.