Dynamic Nutritional Trajectories in Growing–Finishing Pigs: A CRITIC-Based Evaluation and SHAP-Interpreted Final Body Weight Prediction

Phase-specific nutrient supply influences growth performance, nutrient utilization, carcass development, and skeletal health. Dietary strategies are usually evaluated using a limited number of production traits. In this study, 165 pigs were assigned to nutritional trajectories across three body-weight phases: 25–50, 50–75, and 75–100 kg. Four dietary nutrient levels corresponding to 100%, 90%, 80%, and 70% of the reference nutrient concentrations were used. The trajectories included continuous nutrient supply, phase-specific nutrient restriction, nutrient switching, and nutritional recovery. A hierarchical indicator system was established using growth performance, nutrient digestibility, carcass traits, body conformation, energy and nitrogen deposition, bone geometry, trabecular microarchitecture, and bone mineralization traits. The Criteria Importance Through Intercriteria Correlation (CRITIC) method was used to determine indicator weights and calculate domain-specific and overall performance scores. Support vector regression, back-propagation neural network, and random forest models were developed to predict final body weight; SHAP analysis was used to interpret the contribution of input variables. Growth performance, energy and nitrogen deposition, and carcass quality received the highest objective weights. Combining internally validated predictions and model interpretation provides a quantitative basis for designing phase-specific nutritional strategies for growing–finishing pigs. Independent farm, breed, and management condition validation is required before practical application.