@Aceoky
It is the amino acid content that is more important than crude protein. Then the vitamins (especially B's) and mineral traces, which are essential for healthy growth in meat birds and layer production.
Then importantly, bird type. Layers have different mineral needs than meat birds and vice versa. Obviously layers need significantly greater calcium earlier. Study indicates that many layers need both layer feed AND oyster shell or calcite free choice. Meat birds are especially in need of trace minerals such as manganese.
Here are some of those links for you for your own research. Each owner must decide which is most effective for their flock given their flock type, environment, and cost requirements.
Food for thought...and poultry
LofMc
Nutrition Requirements of Poultry, 9th Edition (excerpts)
"Excessive crude protein intakes are to be avoided. Daily intakes of 27 g per hen had adverse effects on hatchability (Pearson and Herron, 1981, 1982). Lower crude protein intakes may be satisfactory if additional amino acid supplementation is practiced. Bornstein et al. (1979) calculated that a daily crude protein intake of 15.6 to 16.5 g per hen would be sufficient in terms of an ideal amino acid mixture. Performance of hens fed corn-soybean meal diets providing 16 g protein per day was not improved by supplemental lysine and methionine. (Waldroup et al., 1976b)."
"Leeson and Summers (1989) concluded that pullet growth is initially most sensitive to dietary protein and amino acids, whereas energy intake becomes more critical as the bird approaches maturity."
There are helpful charts and comparisons in this article showing low protein (less than 15%) vs. high protein (18%) effects. No where does it indicate an above 22% need in layers. Birds tend to eat more or less what they need...higher protein they eat less; lower protein they eat more, assuming adequate amino acids and minerals and vitamins.
https://www.nap.edu/read/2114/chapter/4#33
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Then from the Future Consideration of Poultry Feed Symposium 2011, which recognizes poultry needs have not changed in the last 50 years, and are not expected to change in the next 10 to 15...
On meat birds:
There will be no major change in the nutrient requirements of meat birds and layers over the next 10 to 15 yr, just as they have changed little over the preceding 50 yr. On the other hand, diet formulation, feeding programs, and production goals are continually changing, and these 3 factors effect ever-evolving diet specifications (Leeson and Summers, 2005). Formulation will be dictated by the need to accommodate ever-increasing genetic potential, the need to grow birds on diets containing less pharmaceutical products, and the impact of poultry products on human health. If we want meat birds to achieve ever-increasing weight-for-age or more specifically decreasing age-for-weight, then greater emphasis will have to be placed on both early and late-phase nutrition."
Later on... "Formulating prestarter diets revolves around the selection of highly digestible ingredients rather than there being a need for higher nutrient density"
...and later
Energy Costs
"Both layers and meat birds still eat quite precisely to their energy requirements. The key to successful use of lower-energy diets lies in prediction of change in feed intake and corresponding adjustment to all other nutrients in the diet."
https://academic.oup.com/ps/article/91/6/1281/1547144
As you read that piece, you will find the greatest change in poultry feed is the consumer concerns with removal of antibiotics in the feed and concern over fatty acid contents in eggs and meat (addition of flaxseed and fish oil to poultry diet).
