Replacement of aruana grass by gliricidia (Gliricidia sepium) on silage quality

Our objective was to investigate the effect of the replacement of aruana grass by gliricidia on the fermentative losses, chemical composition, and aerobic stability of silages. For ensiling, whole-crop aruana grass (75 d of growth) was chopped (275 g kg-1 dry matter - DM) and ensiled alone or associated with gliricidia (270 g kg-1 DM; 150 d of growth). For gliricidia, we used only the leaves and stalks to ensile. The evaluated treatments were different ratios of aruana grass to gliricidia (100:0, 75:25, 50:50, 25:75, and 0:100), with four replicates (mini-silos). The silage composed only of gliricidia exhibited a lower pH than the other silages. Dry matter recovery was not affected by the treatments, although effluent losses were affected. The replacement of aruana grass by gliricidia 50% at ensiling resulted in a higher lactic acid bacteria count. The aruana grass silages displayed lower protein contents and a higher neutral detergent fiber content than the gliricidia silages after 40 d of fermentation. Consequently, the silage consisting of 100% gliricidia showed higher in vitro DM digestibility, presenting an increase of 8.13% after 40 d of fermentation compared with 100% of aruana grass silage. After silo opening, the gliricidia silage was very stable (>72 h). The low quality of aruana grass silage is improved by replacing this grass with significant amounts of gliricidia (approximately 75%).

本研究旨在探究以格利西迪亚草（gliricidia）替代阿鲁纳草（aruana grass）对青贮饲料发酵损失、化学成分及有氧稳定性的影响。试验以生长75天的全株阿鲁纳草为原料，将其切碎至干物质（dry matter，缩写DM）含量为275 g·kg⁻¹后，单独青贮或与生长150天、干物质含量为270 g·kg⁻¹的格利西迪亚草混合青贮；本试验仅采用格利西迪亚草的叶片与茎秆作为青贮原料。试验设置阿鲁纳草与格利西迪亚草的不同混合比例处理组（100:0、75:25、50:50、25:75及0:100），每组设置4个重复微型青贮罐（mini-silos）。
仅由格利西迪亚草制成的青贮饲料pH值低于其余所有处理组的青贮饲料。干物质回收率不受处理组影响，但流出液损失量则受处理组显著影响。青贮时以50%比例的格利西迪亚草替代阿鲁纳草，可使青贮料中的乳酸菌（lactic acid bacteria）数量显著升高。发酵40天后，阿鲁纳草青贮饲料的粗蛋白质含量低于格利西迪亚草青贮饲料，而中性洗涤纤维（neutral detergent fiber，缩写NDF）含量则更高。因此，发酵40天后，100%格利西迪亚草青贮饲料的体外干物质消化率较100%阿鲁纳草青贮饲料提升8.13%。青贮罐开封后，格利西迪亚草青贮饲料的有氧稳定性极强（>72小时）。通过以占比约75%的格利西迪亚草替代阿鲁纳草，可显著改善阿鲁纳草青贮饲料品质较低的缺陷。