Qualitative parameters of pearl millet silage ammoniated with urea, at different compaction densities

Abstract: The objective of this work was to evaluate the effects of urea ammoniation of pearl millet silage, at different compaction densities, on chemical composition, losses in the ensilage process, fermentation profile, microbial population count, and aerobic stability. The experimental design was completely randomized, in a 2×4 factorial arrangement, with two compaction densities (600 and 800 kg m-3) and four urea levels (0, 2, 4, and 6% on a dry matter basis), with five replicates. For the aerobic stability assay, the experimental design was completely randomized, in a 2×4 factorial arrangement, with two times (0 and 72 hours) and four urea levels (0, 2, 4, and 6%, on dry matter basis), with five replicates. The urea levels interacted significantly with density as to the contents of organic matter, crude protein, neutral detergent insoluble protein, and as to dry matter recovery; and with exposure hours as to the contents of acid detergent fiber and lignin. Molds and yeasts were not observed in the ammoniated silages. The 800 kg m-3 density reduced losses in the fermentation process of pearl millet silage, and promoted better nutritive value than the compaction at 600 kg m-3. The use of urea does not reduce losses and does not improve the aerobic stability of silages; however, it controls mold growth after silage exposure to air.

摘要：本研究旨在探究不同压实密度下珍珠粟（pearl millet）青贮饲料的尿素氨化处理对其化学成分、青贮过程损失、发酵特性、微生物种群数量及有氧稳定性的影响。本试验采用完全随机2×4因子设计，设置2个压实密度（600 kg·m⁻³和800 kg·m⁻³）与4个尿素添加水平（以干物质（dry matter）计为0%、2%、4%和6%），每组设5个重复。针对有氧稳定性测定试验，本试验同样采用完全随机2×4因子设计，设置2个暴露时长（0小时与72小时）及4个尿素添加水平（以干物质计为0%、2%、4%和6%），每组设5个重复。尿素添加水平与压实密度对有机质、粗蛋白、中性洗涤不溶蛋白（neutral detergent insoluble protein）含量及干物质回收率存在显著交互作用；而尿素添加水平与暴露时长则对酸性洗涤纤维（acid detergent fiber）与木质素（lignin）含量存在显著交互作用。经尿素氨化处理的青贮饲料中未检出霉菌与酵母菌。800 kg·m⁻³的压实密度可降低珍珠粟青贮饲料的发酵过程损失，且相较于600 kg·m⁻³的压实处理，其营养品质更优。尿素的添加虽未降低青贮发酵过程损失，也未提升青贮饲料的有氧稳定性，但可抑制青贮饲料暴露于空气后的霉菌生长。