Swine production and nutrition: W.G. Pond and J.H. Maner, Animal science textbook series, Avi Publishing Co., CT, U.S.A., 1984, 733 pp., price $47.50, ISBN 0-87055-450-6

Abstract

Methionine is the second or third limiting amino acid in typical swine diets, and exogenous methionine supplementation can improve the efficiency of dietary protein utilization by swine when dietary methionine is limiting. Several feed-grade methionine products, such as DL-methionine and DL-methionine hydroxy analogue free acid, have been on the market for feed formulation. Recently, some feed-grade l-methionine products also became available on the market for swine. However, questions often asked by producers and nutritionists are whether or not more crystalline methionine should be used, and which product should be used. Although a simple answer does not exist, this paper was written to comprehensively summarize our current knowledge in methionine nutrition with an attempt to provide a single source of reference for swine nutritionists and scientists to develop more pertinent answers for different swine production systems. Therefore, in this paper, firstly, different forms of commercially available feed-grade methionine products were reviewed chronologically. Secondly, the overall effectiveness of methionine on swine growth performance was summarized. Thirdly, our current understanding of methionine metabolism in animal body was updated. Fourthly, various biochemical and physiological functions of methionine in swine were described. Lastly, dietary methionine deficiency and toxicity to the animal were pointed out. In brief, it is understood from the cellular metabolism standpoint that methionine functions primarily as a substrate for protein and peptide biosyntheses in the body. From a regulatory standpoint, methionine is an initiator amino acid for universal protein translation. Methionine is also an essential source of methyl groups for methylation of at least seven classes of bioactive compounds, such as DNA, RNA, and proteins. Meanwhile, methionine and some of its derivatives are endogenous antioxidants which can protect living cells from oxidative stress. Synthesized from methionine, a myriad of proteins and peptides are involved in immune system for maintaining animal health. Dietary methionine deficiency negatively affects pig growth performance, while supplementation of more methionine may cause toxic effects. Overall, this paper not only can endorse animal scientists to further explore the underlying metabolic and molecular mechanisms that are responsible for methionine nutrition, particularly in pigs, but also can help the field nutritionists to determine methionine requirements of pigs with different production purposes and to selectively use certain commercial methionine products during their diet formulation practice.