Methionine (Met) and lysine (Lys) are the two most studied essential amino acids (AAs) and have been shown to be limiting output of milk protein in dairy cows fed North American rations. Histidine (His) is another of the 10 nutritionally essential AAs that must be provided in sufficient amounts in the diet of lactating cows.

Manure nutrients, a valuable commodity in the past, are becoming an unwanted pollutant. Manure is a natural “byproduct” of milk and meat production from farm animals. In human history, this “byproduct” has always been regarded as a highly valuable source of nutrients and was being applied back to the soil where the nutrients to feed animals originally came from.