Is the total Sulfur Amino Acid:Lysine Ratior for Lactating sows greater than 50%?

Due to increased litter size and milk production in modern sows, the requirements for amino acids have changed. The requirements for essential amino acids other than lysine are typically predicted from the amount secreted in milk and available from body protein. The drawback of establishing essential amino acid requirements in this manner is that not all amino acids are used for milk protein production, with some used for protein deposition and turnover. Along with conversion into protein, methionine also can be converted to Sadenosylmethionine, which acts as a methylating substrate for synthesis of other metabolites. Furthermore, we are only aware of one published study that examines the requirement of sulfur amino acid for the lactating sow. As a consequence, there is little knowledge of the total sulfur amino acid (TSAA) requirement of the modern lactating sow. Calculations based on NRC (1998) recommendations result in a TID TSAA:lysine ratio of approximately 48 to 49%, depending on the level of milk production. The objective of this experiment was to determine whether the TSAA:lysine ratio calculated from NRC (1998) recommendations is adequate for lactating sows. A secondary objective was to determine whether deleting methionine from a diet containing large amounts of synthetic amino acids would alter sow productivity, thus, providing a model to determine the TSAA:lysine ratio for lactating sows in future experiments.