ABSTRACT The aim of this study was to evaluate the effect of two organic acids [malic acid (MA) and citric acid (CA)], Lactobacillus plantarum (LP) and their mixtures on the fermentation of alfalfa silage. The wilted and chopped alfalfa was ensiled in vacuum-sealed plastic bags (200–230 g per bag) with following additives: 0.5% distilled water (control), 0.5% DL-MA, 0.5% CA, LP (1 · 106 cfu/g), 0.5% DL-MA plus LP (MA+LP) or 0.5% CA plus LP (CA+LP) (application rates based on fresh weight). Each treatment had four replicates and was stored at room temperature. After 60 d of ensiling, decreases in pH, non-protein N (NPN) and increases in lactic acid were observed in all additive-treated silages (p < 0.01). Compared with treatment LP, higher pH and lower lactic acid concentrations were observed after MA or CA addition (p < 0.05) and further application of MA or CA together with LP did not promote lactic acid fermentation in ensiled alfalfa. Furthermore, additives decreased the proportion of saturated fatty acids and increased the proportion of polyunsaturated fatty acids in ensiled alfalfa, with the highest level in CA-treated silages (p < 0.05). Although MA and CA were not as effective as LP in improving silage fermentation quality, treatments MA+LP and CA+LP were more effective in decreasing silage NPN, and CA was most effective in inhibiting biohydrogenation of fatty acids in ensiled alfalfa.

中文翻译：

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添加苹果酸或柠檬酸、植物乳杆菌及其混合物对青贮苜蓿发酵品质、蛋白水解及脂肪酸组成的影响

摘要 本研究的目的是评估两种有机酸 [苹果酸 (MA) 和柠檬酸 (CA)]、植物乳杆菌 (LP) 及其混合物对苜蓿青贮发酵的影响。将枯萎和切碎的苜蓿装入真空密封的塑料袋（每袋 200-230 克）中，并加入以下添加剂：0.5% 蒸馏水（对照）、0.5% DL-MA、0.5% CA、LP（1·106 cfu/ g)、0.5% DL-MA 加 LP (MA+LP) 或 0.5% CA 加 LP (CA+LP)（施用率基于鲜重）。每个处理有四个重复，并在室温下储存。青贮 60 天后，在所有添加剂处理的青贮饲料中观察到 pH 值、非蛋白 N (NPN) 和乳酸增加（p < 0.01）。与处理 LP 相比，添加 MA 或 CA 后观察到更高的 pH 值和更低的乳酸浓度（p < 0. 05) 并且进一步应用 MA 或 CA 与 LP 并没有促进青贮苜蓿的乳酸发酵。此外，添加剂降低了青贮苜蓿中饱和脂肪酸的比例并增加了多不饱和脂肪酸的比例，其中在 CA 处理的青贮饲料中含量最高（p < 0.05）。尽管 MA 和 CA 在提高青贮发酵质量方面不如 LP 有效，但 MA+LP 和 CA+LP 处理在降低青贮 NPN 方面更有效，而 CA 在抑制青贮苜蓿中脂肪酸的生物氢化方面最有效。CA 处理的青贮饲料中含量最高 (p < 0.05)。尽管 MA 和 CA 在提高青贮发酵质量方面不如 LP 有效，但 MA+LP 和 CA+LP 处理在降低青贮 NPN 方面更有效，并且 CA 在抑制青贮苜蓿中脂肪酸的生物氢化方面最有效。CA 处理的青贮饲料中含量最高 (p < 0.05)。尽管 MA 和 CA 在提高青贮发酵质量方面不如 LP 有效，但 MA+LP 和 CA+LP 处理在降低青贮 NPN 方面更有效，而 CA 在抑制青贮苜蓿中脂肪酸的生物氢化方面最有效。