IACUCs, the animal version of IRBs, evaluate the potential benefits to both human and animal welfare compared to the suffering of the animals in question - and

IACUCs, the animal version of IRBs, evaluate the potential benefits to both human and animal welfare compared to the suffering of the animals in question - and that a minimum of animals are being used. It's very possible the argument is that this research outweighs the cost of life for these animals. It's also possible this was effectively going to happen anyway. Research animals are often, by law, culled rather than sold or the like, and many researchers do their best to ensure that their sacrifice is not wasted. If they are going to be euthanized anyway, they may be directed to a project like this.