Modeling Dietary Net Energy for Maximum Profitability in Growing-Finishing Pigs

Knowledge of energy use by the pig is essential to predict, optimize, and formulate diets to achieve expected performance. Taking into consideration the productive and financial implications of the energy density of the diet, the objective of this project was to develop a tool to estimate the dietary NE concentration that yields maximum profitability for growing-finishing pigs. A Microsoft Excel®-based model was developed to contrast dietary NE currently utilized by the user with recommended concentrations intended to maximize profitability in user-defined production and economic scenarios. The model is divided into 3 sections: 1) model inputs (including economics, production, and dietary criteria), 2) model calculations and optimization (including growth performance and carcass yield predictions, and profitability indicators), and 3) model outputs (including recommended dietary NE concentrations and profitability indicators). To calculate pig performance, the model uses prediction equations for ADG. Where ADG, g = 0.1135 × NE, kcal/kg + 8.8142 × Avg BW, kg - 0.05068 × (Avg BW, kg)² + 275.99, when Lys or other amino acids are not limiting. To calculate G:F, the assumption is that G:F has a linear relationship with NE in the diet. Therefore, a 1% change in NE will result in a 1% change in G:F. The model also uses the NDF content of the diet to estimate the effect of the diet on dressing percentage, where carcass yield, % = 0.03492 × WP, d – 0.05092 × NDF1, % – 0.06897 × NDF2, % – 0.00289 × (NDF2, % × WP, d) + 76.0769, where WP is the withdrawal period and NDF1 and NDF2 are the NDF levels in the dietary phase prior to the final phase and in the final phase before marketing, respectively. The model predicts responses for an average pig without population variance included. For profitability calculations, a non-linear mathematical programming model was designed to select the optimum values of dietary NE that yield the maximum profitability. In this model, the objective function of income over total cost on a live- or carcass-basis is maximized by selecting the optimal value of NE in each dietary phase. In conclusion, the model herein can be used to predict the value of dietary NE that yields maximum profitability for growing-finishing pigs.