Effects of polyphenols from involucres of <i>Castanea mollissima</i> Blume on the nutritional quality and bacterial community of high-moisture ear corn

High moisture ear corn (HMEC) is widely used in dairy cow diets, but its high moisture content can cause protein hydrolysis during fermentation. This study evaluated the effects of polyphenols extracted from the involucres of Castanea mollissima Blume (PICB) on the nutritional quality and bacterial communities of HMEC at two moisture levels: low moisture (LM, 40%) and high moisture (HM, 45%), using a 2 × 4 factorial design. HMEC was treated with 0% (CON), 0.1% (PICB1), 0.15% (PICB2), or 0.2% (PICB3) PICB. Lactic acid bacteria (15 mg/kg) were applied before ensiling. After 60 days of fermentation, crude protein (CP), dry matter (DM), lactic acid (LA), acetic acid (AA) and ammonia nitrogen (NH3-N) were highly significantly higher (p < 0.01) in LM than those in HM. DM and CP contents were also highly significantly higher (p < 0.01) in LMPICB3 than those in LMCON. LA content of LMPICB3 was highly significantly higher (p < 0.01), while neutral detergent fibre (NDF) and NH3-N content were highly significantly lower (p < 0.01) than other treatments in LM. DM, CP and LA contents were significantly higher (p < 0.01) in HMPICB3 compared to other treatments in HM. Microbial analysis revealed that Lactobacillus was most abundant in LMPICB3, positively correlated with LA. In contrast, Pantoea and Serratia were positively correlated with NH3-N content. Klebsiella was negatively correlated with CP and LA contents. In conclusion, 40% moisture content combined with 0.2% PICB addition resulted in optimal fermentation quality in HMEC, demonstrated by increased LA and CP contents along with reduced NH3-N contents.