西藏地区荞麦与玉米混合青贮对发酵品质和微生物多样性的影响

Effects of variation in proportion of maize on the fermentation quality and microbial diversity of mixed buckwheat and maize silage in Tibet

为探究西藏林芝市全株荞麦与全株玉米混合青贮对青贮饲料发酵品质和微生物多样性的影响,分别设定全株荞麦单独青贮组(A)、全株荞麦∶全株玉米=4∶1混合青贮组(B)、全株荞麦∶全株玉米=3∶2混合青贮组(C)、全株荞麦∶全株玉米=2∶3混合青贮组(D)和全株荞麦∶全株玉米=1∶4混合青贮组(E)共5个处理组。分别在青贮第7、14、30和60天时,开窖取样,测定青贮饲料的发酵品质和微生物菌群结构。结果表明,与全株荞麦单独青贮组相比,全株荞麦与全株玉米混合青贮组在一定程度上改变了青贮的发酵品质,混合青贮组降低了青贮饲料的pH值,提高了乳酸含量,且氨态氮/总氮的值和丁酸含量均符合优质青贮饲料的要求量。从微生物菌群结构来看,混合青贮改变了青贮饲料的菌群结构,相比与全株荞麦单独青贮组,混合青贮组提高了厚壁菌门和LAB菌种的丰度,有效地抑制了腐败菌的生长,且这种效果随着全株玉米混合比例越高而越显著。综合考虑全株荞麦利用最大化和发酵品质,建议将全株荞麦和全株玉米以2∶3混合青贮较为适宜。

This study conducted in Nyingchi, Tibet, explored the effect on silage fermentation quality and microbial diversity of adding whole maize in in various proportions to whole buckwheat, when making silage. The combinations tested were:(A) whole buckwheat alone;(B) buckwheat∶maize mixed at a 4∶1 ratio;(C) buckwheat∶maize mixed at a 3∶2 ratio;(D) buckwheat∶maize mixed at a 2∶3 ratio;(E) buckwheat∶maize mixed at a 1∶4 ratio. On the 7 th, 14 th, 30 th and 60 th day after ensiling, samples were collected to determine the fermentation quality and microflora structure of silage. Compared with buckwheat alone(silage A) adding maize reduced the pH value and increased the lactic acid content of the silage. Both the ammonia nitrogen∶total nitrogen values and the butyric acid content of the mixed silages met the requirements to be considered high quality silage. Maize addition also changed the microflora structure of the silage. Compared with silage A, maize addition increased the abundance of Firmicutes and lactic acid bacterial strains, and effectively inhibited the growth of spoilage bacteria, and this effect was more significant as the proportion of maize increased in silages B to E. Considering the desirability of maximization utilization of buckwheat which is suited to the local climate, and silage fermentation quality, we conclude that silage D with a 2∶3 buckwheat∶maize ratio would be the preferred formulation.