184 Modeling grow-finish pig growth performance responses to variable net energy levels with ingredient nutrient estimations using four energy systems

Abstract The objective of this meta-analysis was to characterize growth performance of pigs from 20 to 130 kg BW based on dietary NE and content of other nutrients. Data from 94 grow-finish pig trials with diets differing in NE were used to predict growth performance based on the diet’s NE, CP, standardized ileal digestible (SID) Lys, NDF, and Lys to NE ratio. Energy and nutrient concentrations in all diets were determined using the values from four different databases (NRC, 2012; CVB, 2022; INRA, 2024; Rostagno et al., 2024). Backward stepwise selection using Akaike information criteria was used for model selection considering the linear, quadratic, and interactions of NE, SID Lys, CP, NDF, Lys to NE ratio, and pig BW. Model estimators were predicted using a linear mixed model with experiment included as a random effect. The selected models were able to predict the influence of NE in the magnitude of the responses’ change when the following input ranges were used: 40 to 125 kg BW, 2.20 to 2.80 Mcal NE/kg, 0.50 to 1.20% SID Lys, 10.4 to 19.0% CP, 7.9 to 19.8% NDF, and 2.20 to 5.20 Lys:NE ratio. The selected models indicated that ADG and G:F improved as dietary NE increased for the four energy systems evaluated. However, the response magnitude differed for each model for each additional Mcal of NE, with the predicted G:F responses differing between energy systems at the early and late stages of the finisher period. In addition, the model using Rostagno and Albino (2024) nutrient values overestimated the predicted ADG when using high NDF levels. The models with all 4 databases also predicted greater changes in ADG and G:F when the Lys to NE ratio was maintained compared to when a constant SID Lys level was maintained as NE increased (NRC example in Figure 1). In conclusion, the model provided estimates of the magnitude of the response change for ADG and G:F for pigs between 40 to 125 kg when using NE, SID Lys, CP, NDF, Lys:NE ratio in the ranges suggested, improving the ability to predict growth performance changes with changes in dietary NE.