Effects of Extruded Corn with Different Gelatinization Degrees on Feed Preference, Growth Performance, Nutrient Digestibility, and Fecal Microbiota of Weaning Piglets

**Background:** Weaning stress in piglets causes reduced feed intake and growth performance due to abrupt environmental and dietary changes. Corn is a major energy source in piglet diets, and extrusion—a thermal-mechanical process—can improve starch digestibility and palatability by altering gelatinization. However, the optimal degree of gelatinization for weaning piglets was unclear, as prior studies reported inconsistent results. This study aimed to quantify the effects of different gelatinization degrees of extruded corn on feed preference, growth performance, nutrient digestibility, and fecal microbiota in weaning piglets.

**Methods:** Two experiments were conducted. In Experiment 1 (preference trial), 144 piglets (35 days old, 9.45 ± 0.76 kg BW) were allotted to six treatments with four replications per treatment (6 piglets/replicate). Each treatment offered a choice between two of four diets: conventional corn (NC; 12.65% gelatinization) or extruded corn with low (LEC; 41.82%), medium (MEC; 62.60%), or high (HEC; 89.93%) gelatinization for 18 days. Feeders were switched sides every three days. In Experiment 2 (performance trial), 144 piglets (34 days old, 9.24 ± 0.55 kg BW) were allotted to four treatments with six replications per treatment and fed one of the four diets for 28 days. Growth performance (ADG, ADFI, F:G) was measured at days 0, 14, and 28. Nutrient digestibility was assessed using chromic oxide as an indigestible marker during the final four days. Blood samples were collected on days 14 and 28 for serum analysis (TP, ALB, GLB, TC, GLP-1, leptin). Fecal samples on day 28 underwent 16S rDNA gene sequencing (V3–V4 region) for microbiota analysis. Statistical analyses included t-tests, one-way ANOVA with LSD, linear and quadratic regressions, and Kruskal–Wallis/Wilcoxon tests for microbiota data.

**Key Results:** In the preference trial, LEC showed the highest relative preference (67.02%) and feed consumption (408.95 g/d), significantly higher than NC, MEC, and HEC (p < 0.05). Relative preference and feed consumption showed a quadratic increase with gelatinization degree (p < 0.05). In the performance trial, LEC and MEC significantly decreased F:G during 14–28 days and 0–28 days compared with NC and HEC (p < 0.05), with a quadratic decrease in F:G during 14–28 days (p < 0.05). No significant differences were observed in BW, ADG, or ADFI among treatments (p > 0.05). For nutrient digestibility, LEC and MEC groups showed higher ATTD of CP than NC and HEC (p < 0.05). MEC also showed increased ATTD of EE compared with NC and HEC (p < 0.05). ATTD of CP and EE showed quadratic increases with gelatinization degree (p < 0.05). On day 14, LEC showed the highest plasma TP and GLB levels, significantly increased compared with NC (p < 0.05). No differences were observed in GLP-1 or leptin levels. Microbiota analysis revealed that extruded corn increased the relative abundance of Bacteroidetes at the phylum level (from 46.05% in NC to 50.37–51.92% in extruded groups; p < 0.05). At the genus level, LEC and MEC increased Lactobacillus, Alloprevotella, Prevotellaceae_UCG-003, and Prevotella_2 compared with NC (p < 0.05). The MEC group tended to have increased observed species (p = 0.090) and Chao-1 index (p = 0.106). Beta-diversity analysis showed separation of NC microbiota from extruded corn groups.

**Clinical Implications:** This study demonstrates that extruded corn with a gelatinization degree of approximately 41.82–62.60% optimizes feed preference, feed efficiency, and nutrient digestibility in weaning piglets while promoting beneficial gut microbiota (increased Bacteroidetes, Lactobacillus, and Prevotella). These findings provide practical guidance for feed formulation to mitigate weaning stress. The quadratic relationship between gelatinization degree and outcomes indicates that over-processing (89.93% gelatinization) reduces benefits, likely due to increased pellet hardness and potential Maillard reactions. Limitations include the lack of significant effects on ADG and ADFI, suggesting that under single-diet feeding conditions, nutritional requirements may override palatability effects. Further research is needed to clarify the mechanisms by which gelatinization degree influences intestinal viscosity and microbial fermentation.