If the by - products are from organ meats like liver kidney, or vegetable material like soybean, then the nutrition is excellent. (lbah.com)
As this chart shows, it is the animal foods, especially organ meats like liver, that provide the most nutrients. (westonaprice.org)
In traditional hunter gatherer societies, the whole of an animal was eaten, with generous helpings of organ meats like liver and connective tissues. (supernaturalacnetreatment.com)