strictly breastfed vs half formula/half beast milk? what do you ladies think?

My son is breastfeed but a few days ago my mom watched him and gave him 4 oz of formula (we have a can just in case) and it fucked up his stomach. While I agree fed is best in my case breast is the only option.

And to empty them out.

Fed is best. If you feel comfortable and are able to exclusively breastfeed/pump that's great. If you feel that it's best to do both, that's great too. If you are doing formula too, make sure when you give formula you pump instead so your supply doesnt drop.

From my stand point Breast is best I breast fed both kids but.. I was just in the hospital and couldn’t really even pump. My sister had him and he wouldn’t even take formula. If I had him try it every once and a while he would have been fine. It made me wish I would have switched it up. But if you do that you must pump so you don’t lose milk