Speaking from experience with processing my own birds... if you are planning on feeding them a high protein starter feed and then a high protein grower feed until processing so they grow quickly (like they should) then they should be ready at around 14 wks. Some of them may be ready at 12 wks, some may be ready at 16 wks tho, depends on the individual bird and how hearty it is, where it is in the pecking order and how well it eats. I don't know about Jumbos, but with regular Helmeted Guinea Fowl there's typically not much growth/meat weight gain after the 14th wk (at least not enough to justify another bag of feed in hopes of them gaining another 1/2 lb or so). There's really not much meat on regular Guineas, and they are lean by nature, so my advice is to feel their breast prior to processing them... start with the heavier/meatier birds first, and give the others another week or 2 longer to grow a little more if they need it.
