Soybean meal (SBM) has been shown to have positive impacts on finishing pig growth performance. In one USB supported project, (USB 1930-352-0509 Determining the Productive Energy Content of Soybean Meal), we observed that SBM contains greater amounts of net energy (NE) than previously estimated. In our next project (2240-352-0514-L, Maximum allowable soybean meal levels in swine diets), improvements in average daily gain and feed efficiency were observed with increasing amounts of SBM in the diet, even when the SBM energy levels were adjusted. Therefore, we believe the next logical step is to evaluate if this improved performance is due to SBM’s greater energy content or a Lys:Calorie ratio response. We will formulate a negative control diet with low SBM levels and a positive control diet with high SBM levels, both assuming SBM to have NE = 100% of corn. The third and fourth diets will have low SBM levels with SBM assumed to have 78% the NE of corn. The third diet will contain added fat to equal the diet NE in the positive and negative control diets. The fourth dietary treatment will have increased lysine to determine if the lost performance of low SBM diets is because of a lower L