First, no dual purpose bird is going to put on weight like a Cx or a quality broiler in those strains where breeders have worked hard to put meat back on the bone.
Second. To the extent it *may* be valuable to you,
here is what Cobb-Vantive recommends for finishing the 500 (p10). Note that Lysine levels remain very high, though total crude protein has reached more typical feed numbers in the finishing weeks. Lysine is key to big breast development, a hallmark of the Cx. If your bird doesn't have genetics for a big breast, some of that will be wasted, of course. Now look alse ot the MJ/kg - as the crude protein has been coming down, total energy (often in the form of fat) has been coming up.
That's pretty typical of the literature and the recommends for putting weight on table birds for decades. Here's
a more generic source. Start on slide 20. and if you want to just jump straight to the charts,
this is what UGA offers (half way down). If you look for recipes, you will often find the proportion of corn rising in the mix, and sometimes even the addition of corn oil or similar to get fat content up around 6% and lots of easy calories.
Obviously, keep feed available at all times, and to the extent you can, restrict activity. Birds that are ranging consistently grow more slowly.
Just kidding of course, hope they make it to 5lb for you!
