What do you mean by "bred?"
If you mean were they raped, yes, yes they were.
If you mean were they collectively put into cramped corners and ended up fucking after so long, that typically happens with everybody in every station of life. Surely you've had a job or been in school. This said, that we also know that slaves would frequently abort their pregnancies, kill themselves, and even poison their own children to spare them the life of a slave.
Part of the reason that the Atlantic slave trade was so expansive was because a lot of them died and it didn't matter how many were lost as it was cheaper to go get more than to keep slaves in safe conditions. In 1833, when the British outlawed slavery and tried to police the slave trade (conveniently after they had been kicked out of most of their slave colonies) there was a forced attempt to create more slaves in the given area. If you look at the US census from that time on, you can see how the categorization of what constitutes a black person continues to exist as American ships came in for a bit—but then rather quickly fall to the, "one drop rule," as slaves become more scarce and then outlawed entirely:
Pew wrote:In the 1850 census, enumerators were instructed to record blacks, mulattos (generally defined as someone who is black and at least one other race), black slaves, and mulatto slaves separately. In 1890, the racial categories of “quadroon” (defined as one-fourth black blood) and “octoroon” (one-eighth or any trace of black blood) were introduced. In 1930, for example, the “one-drop rule” included in enumerator instructions said that “a person of mixed White and Negro blood was to be returned as Negro, no matter how small the percentage of Negro blood.”
By 1890 there is no slavery, but there is a legal category that all people of African ancestry at all must fall into, reflecting the fact that the human breeding you're speaking of, was almost certainly white master raping black slave and then deciding whether their heirs were "legitimate" or slave. As noted:
Ibid wrote:It was not until 1960 that people could select their own race. Prior to that, an individual’s race was determined by census takers, known as enumerators.
This being all said, the OP and the responses, sans Decky, look to have been made with no research or knowledge and typed with one hand.
Alis Volat Propriis; Tiocfaidh ár lá; Proletarier Aller Länder, Vereinigt Euch!