Peas, like any grain, have average values and weights when it comes to stats. However, feed companies get samples in and test them for protein and use those values to base their mixes on in addition to what's been said previously on this thread.
http://www.rayglen.com/crop-bushel-weights/
For example, wheat's base weight per bushel is 60. The wheat I'm currently using for the chickens is heavy with a 69 lbs/bushel weight and it has a high protein value over 13.5...very nice with low/no mycotoxins.
Each field and even each load of grain can have a different protein value. Protein values tend to increase when the grain gets stressed; hot weather, lack of rain etc. It can be influenced by the timing of fertilizers etc as well. Processed feed will have the values listed...but if sourcing from a farmer, just know the protein values can differ. They should be able to provide you with it's protein value if they've gotten it tested at a grain company. Here, testing is done free to determine the quality and thus the price point offered by the grain company.
Not every field pea is equal. I requested to grow field peas this year and we've put in 70 acres for the chickens and the sheep. Our very helpful crop specialist called their animal nutritionist to locate appropriate varieties. I wanted a variety with low trypsin-inhibitor values that averages a higher protein value and is resistant to lodging. Low trypsin inhibitor values are important when looking at peas. In general, peas are one of the safer feeds. Grains high in trypsin inhibitors like soybeans is why these feeds can't be fed raw to livestock and must be heat treated for livestock. I can get complex...lol.
https://www.sciencedirect.com/topics/neuroscience/trypsin-inhibitor
http://articles.extension.org/pages/70164/including-field-peas-in-organic-poultry-diets
We've used feed peas in a blend for our breeding ewes and lambs. Peas work very well for finishing hogs and lambs. They give a great flavour to the meat. However, this is the first time we'll be incorporating peas for feed for the chickens. We used peas specifically as a smaller percentage of my feed ration for keeping good weight on the ewes but not high enough to reduce milk production. We consider it a fairly rich animal feed. I'm hoping our peas turn out.
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