Put the summary of the bug you're having here

What I expected to happen was when the baby animal grew up it would stay unhurt in the 1 by 1 block space

What actually happened was when the baby animal grew up it started taking damage

Steps to Reproduce:
1.make a 1 by 1 block space 2 high so no animals can escape
2.spawn a animal(saves finding one)in the 1 by 1 block space
3.spawn the same animal but click on the first to make a baby.

(I have tried this with chicken,cow and mooshroom)