I just get canned mackerel and/or salmon. A tall can is about $2 and I divide it up into two portions, feed one now, one in a week or so. Sometimes I mix it with oatmeal, olive oil and yogurt. They really love it.
For regular laying hens, 16% is adequate protein. I use the 22% when some are molting heavily, though. For the breeding flocks, I try to run some Game Bird Breeder/Layena (with animal protein) through them on occasion. Helps with hatchability of chicks at 20% protein and is formulated for helping to hatch healthy chicks.
Some brands with animal protein are ADM Alliance Pen Pals, Tucker Milling, Faithway Feeds, and I think Dumor (though I never will buy from
TSC if I can help it and have never used that feed) They use porcine (pork) products as the protein.
Purina's Game Bird feeds do have animal protein in them as well.
Mad Cow came from feeding dead cows to cows, who are herbivores. There is no Mad Pig or Mad Chicken disease that I'm aware of. The feeds say no ruminants are used in the feed, so they use decent quality pig protein, at least the ones on the labels I've read.