Feathers are 92% protein, which is why chickens eat them when they feel deprived.
It can be any fish. The reason I suggest mackerel is because it is much cheaper ounce to ounce than tuna or salmon and is at least as nutritious. It comes in a can so it won't go bad till you open the can. You can keep a couple cans on hand and occasionally, give them a treat. They won't need the supplement every day but for growing birds, they make good use of the essential amino acids.
A good way to look at the relationship between crude protein and essential amino acids is the rain barrel example. It doesn't matter how high the crude protein is, the benefit is constrained by the limiting amino acid.
The following example is for swine but it holds true for all living creatures.
https://www.asi.k-state.edu/extensi...y of describing a,level of the shortest stave.
This is a graphical representation.
https://www.researchgate.net/figure...nthesis-due-to-the-lack-of-an_fig20_333729916
To further belabor the point, protein tends to be expensive.
When feeding a high protein diet that is in excess of what an animal can use (this includes all the protein over and above the limiting amino acid), the excess protein needs to be processed by the liver and expelled by the kidneys. It works both organs harder than necessary. That protein ends up as nitrogen and ammonia in the bedding. If you occasionally put get down and put your nose at the level where chickens breathe and you smell ammonia, they are getting too much protein in some fashion. That is also hard on their fragile respiratory systems.
You come at this much better prepared than new chicken owners because you raised guineas. Any exposure to livestock gives the prudent observer insight.
It can be any fish. The reason I suggest mackerel is because it is much cheaper ounce to ounce than tuna or salmon and is at least as nutritious. It comes in a can so it won't go bad till you open the can. You can keep a couple cans on hand and occasionally, give them a treat. They won't need the supplement every day but for growing birds, they make good use of the essential amino acids.
A good way to look at the relationship between crude protein and essential amino acids is the rain barrel example. It doesn't matter how high the crude protein is, the benefit is constrained by the limiting amino acid.
The following example is for swine but it holds true for all living creatures.
https://www.asi.k-state.edu/extensi...y of describing a,level of the shortest stave.
This is a graphical representation.
https://www.researchgate.net/figure...nthesis-due-to-the-lack-of-an_fig20_333729916
To further belabor the point, protein tends to be expensive.
When feeding a high protein diet that is in excess of what an animal can use (this includes all the protein over and above the limiting amino acid), the excess protein needs to be processed by the liver and expelled by the kidneys. It works both organs harder than necessary. That protein ends up as nitrogen and ammonia in the bedding. If you occasionally put get down and put your nose at the level where chickens breathe and you smell ammonia, they are getting too much protein in some fashion. That is also hard on their fragile respiratory systems.
You come at this much better prepared than new chicken owners because you raised guineas. Any exposure to livestock gives the prudent observer insight.