Regarding protein, I wanted to add that % of crude protein can be misleading, especially if people are mixing ingredients. The % on a bag of feed or reported as the content of an ingredient is crude protein. It doesn't differentiate between the makeup of essential amino acids.
Since most feeds are vegetarian (grains and legumes), feed manufacturers usually need to add synthetic lysine, methionine and sometimes other amino acids to make up what is missing in the vegetable based ingredients to meet the needs of omnivorous chickens.
There are ways of looking at amino acids as a barrel with each stave being one of the essential amino acids. If one is short, the others are excessive and the ingredients will spill out so even though the crude protein content may be high, there can still be deficiencies.
The excesses of some amino acids will be excreted as nitrogenous waste and result in high ammonia in the litter.
What feed companies do to correct this is to keep the crude protein as low as possible and supplement the deficient amino acids so the overall cost of protein and nitrogenous excrement is kept as low as possible.
Sometimes, in feeding, I accomplish this by using a 16% organic grower feed for most birds and mix in 60% fishmeal depending on the needs of the birds. The animal based fishmeal will have much higher ratios of amino acids that are deficient in the vegetable based feeds. A 10:1 mix of 16% grower to fishmeal will provide 20% protein for chicks and molting birds.
Limiting amino acid theory.
https://puyallup.wsu.edu/lnm/wp-con.../Protein-and-amino-acid-for-poultry-final.pdf
I'm really lucky in that the feed I buy uses fish meal as the primary protein source, with spring peas (not soy) providing additional protein. And believe me, if I allow the feed to ferment too long, I can DEFINITELY smell the fish meal.