Bringing an animal into existence for the purpose of abusing, using and harming them is not ethical under any circumstance. If we breed dogs for dogfighting, the harm inflicted on the dogs by the fight is still not morally acceptable. If we breed bulls for bullfighting, the suffering inflicted on them is never justified.
The animals that are being used and killed do not care about why they were bred, they just want to live and avoid suffering. It is not our right to go against those interest just because we brought them into existence.