I don't have any meat birds, they are various breeds of egg layers. And they do have a grit bowl too. I haven't seen any all flock at the feed store, but I think they have a flock raiser. The reason I mentioned the feather fixer feed is because the bag said for hens and roosters over 16 weeks of age. That one was also 18% protein if I remember correctly, or maybe 20%. Would still need calcium supplement with that one too. Thanks.
Keep in mind the Feather Fixer has 3.25% calcium. Not as high layer feed but higher than some suggest. Feeding layer never hurt my roosters, YMMV.