Page 9 of articles about amino acids
Lysine to metabolizable energy ratio affects growth performance, blood metabolites and hormones of lactating sows
Lipid metabolism in pigs fed CLA and/or dietary arginine

Nutrition and intramuscular fat: Effect of the levels of protein, lysine and other amino acids
The decrease in the level of protein seems to be a promising strategy to increase the intramuscular fat, as long as the lysine level is adapted to the to the kind of pig used.