I not sure if this is a bug or not but 2 of my horses have 100 energy. It just hit me today that if upgraded with specialty breed =80 and you can only add 10 extra on once that should be 90. The horses in question are (ID #239458) and (ID #237634). When I bought them they had 90 energy but after they came to my account it turned to 100. But it really never crossed my mind until today. Oh they are on this account (#18278) and I bought them from 2 different accounts.  So they didn't come from the same account.

They can go up to 100 energy if you buy extra from the cash shop. So it's possible the previous owner did that?