The United States Conference of Catholic Bishops (USCCB) has decried a proposal by the National Institutes of Health to fund human/animal chimera research.
This is not surprising. With genetic engineering research already going on with humans, the idea of doing whatever you want with humans is a - for some - logical next step. Man recreates man to function in ways outside of his current capabilities or to enhance capabilities he already has. I could list a bunch of reasons but it’s not necessary. It would not surprise me if the military was the first beneficiary of any “successful” experiments.
Destroying human embryos in doing this is killing unique human beings.
Get a copy of The Abolition of Man by C.S. Lewis. It’s all there.