Does butchering non-adult tame animals give the same amount of meat, skin, etc. as a grown animal of the same kind?
No, you will receive less resources for slaughtering animals before they are fully grown.
My advice would be to check the wiki which has details about the resources gained from slaughtering animals to decide whether it is worth it or not.
It is also worth considering how much grazing space each animal needs (because animals that die of starvation cannot be slaughtered), and if you have a breeding pair of animals.
As a general rule, the amount of meat, fat, and bones received from slaughtering animals tend to vary the most between slaughtering fully grown and young animals. Other items, such as brain, heart, lungs, raw hide, etc. tend to remain constant.