Growing-finishing pigs should consume daily the minimum amounts of energy and amino acids needed for maximum lean deposition. This should optimize performance traits, carcass leanness and nitrogen excretion. These ideal conditions are difficult to achieve under experimental or farm conditions due to factors that affect amino acid requirements and daily feed intake. Lean deposition rates and sex are two of the major factors that affect amino acid requirements. Knowing the lean deposition rates for the herd will allow the development of custom feeding programs Segregating pigs according to sex will improve the ration's nitrogen utilization.

Over the years there has been a lot of research on developing amino acid requirements of swine. Apparent ileal digestibility of amino acids has been used to estimate amino acid absorption. Knowing the amino acid requirement and digestibility of the amino acid in the diet, one can formulate diets that can meet the animal's amino acid requirement without wasteful excesses. Crystalline amino acids can be used to improve amino acid balance and reduce excessive intake of protein. While synthetic amino acids can replace supplemental proteins, their effect on carcass quality is still uncertain.

Excretion of nitrogen in manure can be minimized by matching the amino acids needs to the amino acid supply, increased use of crystalline amino acids to lower the dietary protein level and the use of highly digestible protein ingredients, such as soybean meal. Soybean meal's amino acid composition complements the amino acid profile of feed grains to minimize nitrogen waste and maximize performance of the growing-finishing pig.

Knabe, D.A. 1996. Optimizing the protein nutrition of growing-finishing pigs. Animal Feed Sci. and Tech. 60:331-341.