不同品种葡萄渣对苜蓿青贮品质和有氧稳定性的影响

为探究不同品种葡萄渣对紫花苜蓿蛋白水解和有氧稳定性的影响,采用“甘农四号”紫花苜蓿作为青贮原料,分别添加马尔贝克(MC)、美乐(MT)、蛇龙珠(CG)3个品种葡萄渣50、100和150 g·kg^-1调制青贮饲料。试验共设置10个处理组,对苜蓿青贮后发酵品质、蛋白组分、蛋白质降解酶、微生物数量及有氧稳定性进行测定及分析。结果表明:3种葡萄渣在100和150 g·kg^-1的添加量下,均显著降低了青贮pH值(P<0.05);非蛋白氮含量随葡萄渣添加量增加而下降,以马尔贝克150 g·kg^-1最低,为430.25 g·kg^-1;添加葡萄渣降低了青贮中氨态氮含量,但添加量的变化对氨态氮含量影响不明显;美乐150 g·kg^-1对青贮羧基肽酶抑制作用最强,酶活性由17.56 μmol·h^-1下降至6.51 μmol·h^-1;葡萄渣增加了青贮发酵后乳酸菌数量,且抑制了霉菌的生长,蛇龙珠150 g·kg^-1乳酸菌数量最高,对照霉菌数量为3.02 log₁₀ cfu·g^-1,显著高于其他处理(P<0.05);3种葡萄渣均减缓了青贮有氧暴露阶段霉变腐败速度,其中美乐150 g·kg^-1处理组有氧腐败所用时间最长。综上所述,不同品种葡萄渣均能改善苜蓿青贮发酵品质,抑制蛋白酶活性,减少青贮蛋白水解程度,并提高了苜蓿青贮有氧稳定性。

Effects of different grape variety on proteolysis and aerobic stability of alfalfa silage made with added grape pomace

The aim of the present study was to determine the effects of pomace from different grape varieties on the proteolysis and aerobic stability of alfalfa silage. The alfalfa (Medicago sativa) variety “Gannong No.4” was used as the base material for the silage, and pomace of three grape varieties Malbec (MC), Merlot (MT) and Cabernet gernischt (CG) were added at rates of 50, 100 and 150 g·kg^-1, making a total of 10 treatment groups, including a control (CK) without added grape pomace. Silage fermentation quality, protein components, pH, activities of proteolytic enzymes aminopeptidase and carboxypeptidase, microbial counts and aerobic stability were determined. It was found that all grape pomace significantly (P<0.05) reduced the silage pH when added at 100 and 150 g·kg^-1. The non-protein nitrogen content decreased with increasing supplementation rate of the grape pomace. MC added at 150 g·kg^-1 had the lowest non-protein nitrogen content (430.25 g·kg^-1). Adding grape pomace reduced the content of peptide nitrogen in the silage, but peptide nitrogen content did not vary significantly with the rate of pomace added. MT added at 150 g·kg^-1 had the strongest inhibitory effect on silage carboxypeptidase; enzyme activity declined from 17.56 μmol·h^-1 to 6.51 μmol·h^-1. Addition of grape pomaces increased the lactic acid bacteria count after silage fermentation, and inhibited the growth of mold. The highest lactic acid bacteria count was for CG added at 150 g·kg^-1. The number of fungi in CK was 3.02 log₁₀cfu·g^-1, significantly (P<0.05) higher than other treatments. Addition of all three grape pomaces slowed down the rate of fungal spoilage during aerobic exposure and the MT treatment group was stable for the longest time before showing aerobic decay. The above results indicated that the pomace of all three grape varieties improved silage fermentation quality, inhibited activity of silage proteases and reduced the degree of silage protein hydrolysis, and improved the aerobic stability of silage.