Effects of Distillers Dried Grains with Solubles Replacing Soybean Meal on Pelleting Characteristics of Mash Feed and Optimization of Processing Parameters

Highlights Investigated the key impacts of DDGS replacement ratio on feed processing. Elucidated the effects of key processing parameters on pelleting characteristics and determined the optimal processing parameters. Established a prediction model for pelleting characteristics based on response surface methodology. Abstract. This study investigated the effects of replacing soybean meal with Distillers Dried Grains with Solubles (DDGS) at different proportions on the physicochemical and pelleting characteristics, as well as pellet quality of corn-soybean meal mash feed. A Box-Behnken design was used with replacement ratio (0%, 25%, 50%), conditioning temperature (75, 80, 85℃), and conditioning time (45, 135, 225 s) as independent variables, while power consumption per ton, pellet formation rate, and pellet durability index served as dependent variables. A total of 17 pelleting experiments were conducted. The results showed that: (1) Increasing DDGS replacement ratio significantly decreased angle of repose, angle of friction, apparent density, and tapped density, but increased compressibility (P < 0.05); it also significantly decreased peak viscosity, trough viscosity, final viscosity, and setback, while increasing pasting temperature (P < 0.05). Higher replacement ratios gradually decreased power consumption per ton and pellet durability index, while pellet formation rate initially increased then declined at approximately 18% replacement. (2) With increasing conditioning temperature, power consumption per ton initially decreased and then increased at approximately 82℃, whereas pellet formation rate and pellet durability index peaked at about 79℃ and 81℃, respectively. Prolonged conditioning time reduced power consumption per ton initially and then increased, with opposite trends for pellet formation rate, transition periods for both ranged 70–145 s, while the changes of pellet durability index were relatively small. (3) Variance analysis indicated that DDGS replacement ratio had the greatest effect on pelleting characteristics, followed by conditioning temperature and time. Response surface methodology established reliable predictive models for pelleting characteristics under different replacement ratios. Overall, replacing soybean meal with DDGS significantly reduced power consumption per ton, although an excessively high replacement ratio adversely affected the pellet quality.