Protein is the second most expensive nutrient after energy in swine rations. While essential amino acids have been looked at extensively regarding requirements needed, total dietary nitrogen and non-essential amino acids have not. Pigs can use non-protein nitrogen to correct essential amino acid deficiency, though it is not a viable dietary alternative as it may not be efficient enough. Non-protein nitrogen absorbed from the hindgut can be used efficiently under conditions of dietary non-essential amino acid deficiency or total nitrogen deficiency for body protein deposition. These results may not replicate in commercial practices.
The Importance of Nitrogen for Growth (full article)