It’s a copy from the original minion that pops up, so if the original minion doesn’t have a Deathrattle, the new minion won’t have one either. So any cards that receive a Deathrattle (because of a Battlecry or spell) won’t have a Deathrattle when they return. The whelps summoned by Vectus are 1/1’s who receive their Deathrattle from Vectus, but don’t have it on their own.