rottweiler in heat

Question
i have a mixed breed rottweiler in heat, is she to old to breed she's almost 4 she's never been in heat before

Answer
Four is old for her to come into her first heat. That is a indicator that there are health issues you may not see.

Before I did any breeding I would have her thyroid tested to make sure she doesn't have a condition that would be passed on to her off-spring.

Good luck