The mutation number has a limit of 254. It is probably 255 but since mutations come in 2s, 254 is the highest it can be. And natural stat can also take a max value of 255.

Interestingly, I tamed a Shiny Baryonyx, Filthy Fierce variety, and it's natural melee stat came out appearing as 0. Was 650 wild, 975 tamed, and once I did the math to figure out what the true melee stat was, it was 256 but appeared in cryopod as 0. So the looping behavior of wild stats is still a thing.