When you have two dogs and you try to mate them, their baby comes with the life almost to the minimum, this is a bad thing, since if you want to mate that baby with another dog, you have to cure it before and it makes you spend a lot of food resource.
Thank you for your report!
We're actually already tracking this issue in MC-27287, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.