Optimization of moisture content and application rate of hay preservative during high‐moisture alfalfa hay baling in northwestern China

Background Leaf shatter during low‐moisture baling and mold proliferation under high‐moisture conditions pose major challenges in alfalfa hay production. A proprietary propionic acid‐based hay preservative product, LZP, effectively inhibits microbial reproduction in high‐moisture alfalfa bales; however, its optimal moisture thresholds and application rates remain undefined. Methods A two‐factor design tested baling moisture (Low, 17%–21%; High, 21%–26%) and the LZP application rate (0, 4, and 6 L t −1 ), with conventional dry bales (below 15%) as a control. Results Low‐moisture bales treated with 6 L t −1 LZP showed temperature characteristics and mold and yeast counts comparable to those of the control while reducing the maximum temperature by 23.1°C and heat degree days above 30°C (60 days) by 153°C·d compared with low‐moisture bales without LZP (0 L t −1 ). Although microbial growth was inhibited in high‐moisture bales treated with 6 L t −1 LZP, severe mildew occurred in the bale cores. LZP significantly reduced neutral and acid detergent‐insoluble crude protein (NDICP, ADICP) at both moisture levels relative to untreated bales ( p < 0.05). Antifungal efficacy was greater in low‐moisture bales treated with 4 or 6 L t −1 than in the corresponding high‐moisture bales. Conclusions The optimal baling moisture and LZP application rate were determined to be, respectively, 17%–21% and 4–6 L t −1 .