Is It Ok For My 4 Month Old Pit Bull Puppy To Start Eating Adult Dog Food?

I don't think it will necessarily hurt..but, the puppy food is better, softer on the teeth.

I would say stick with puppy kibble. My dog preferred Purina Puppy Chow and even though she just turned 2 I fed her some about 6 months ago.  Most vets recommend the hard kibble. 

I have raised several pit bull puppy's, you should feed your puppy puppy chow for at least the first 12 months. Buy it in 40 pound bags it's a lot cheaper.

No. Puppy food is richer in protein which is crucial for your growing pup. In about 4 months, when he/she is 8 months you can put him/her onto adult food.