Impact of Alternative Energy Systems on the Estimated Feed Requirements of Pigs with Varying Lean and Fat Tissue Growth Rates When Fed Corn and Soybean Meal-Based Diets

Swine growth models can be used to predict the nutrient requirements, feed costs, and economic returns of specific genetic populations of pigs. The objectives of this study were to 1) predict changes in energetic and economic efficiency of 2 genetic populations of pigs with different compositional growth rates; 2) compare the predictions of 3 energetic models — 2ME based systems and a NE based system (ME-Noblet, ME-Tess, and NE), and 3) evaluate the impact of predicting maintenance energy requirements as a function of BW or lipid-free empty BW when fed corn-soybean meal based diets. The higher lean-gain (HLG) pigs had lesser rates of lipid deposition (423 vs. 356 g/d), greater protein deposition (101.89 vs. 106.0 g/d), and similar BW growth rates as the lesser lean-gain (LLG) pigs. Overall, the ME-Noblet and NE energy systems predicted similar feed intakes, diet composition, feed costs, and similar differences between the genetic populations and sexes. The HLG pigs were predicted to require 28.4, 29.9, and 30.1kg less feed and to have 33.5, 34.1, and 29.1% greater lean efficiency (carcass lean-gain:feed intake) than the LLG pigs from 25 to 125kg based on the ME-Noblet, NE, and ME-Tess equations, respectively. The prediction of maintenance requirements based on BW or lipid-free empty BW had little impact on the predicted differences between the 2 genetic populations. The 3 energy systems predicted similar differences in feed intakes and feed costs between the HLG and LLG pigs.