添加剂对紫花苜蓿青贮饲料发酵品质的影响

Effects of additives on fermentation quality of alfalfa silage

为提高紫花苜蓿青贮饲料的发酵品质,抑制不饱和脂肪酸的损失,以无添加剂为对照,研究了添加剂:苯甲酸钠、酪蛋白酸钠、十六烷酸、糖蜜和丙酸,对紫花苜蓿青贮饲料发酵品质和脂肪酸的影响。青贮65 d后开窖,检测发酵品质指标和各种脂肪酸的含量。结果表明:对照组的pH低于4.50,乳酸含量达到54.25 g·kg^-1 DM,丁酸含量低于5.00 g·kg^-1 DM,弗氏评分为64.33,具有良好的发酵品质。与青贮前相比,青贮后苜蓿青贮饲料中的亚油酸(C18:2n6)和亚麻酸(C18:3n3)的含量显著增加(P<0.05)。青贮后,与对照组相比,十六烷酸和酪蛋白酸钠添加组分别不显著(P>0.05)和显著地(P<0.05)降低了乳酸含量;酪蛋白酸钠添加组增加了丁酸含量(P<0.05);二者的弗氏评分低于50.00,降低了发酵品质。与此相反,苯甲酸钠、丙酸和糖蜜添加组不同程度地增加了乳酸含量,降低了pH,减少了氨态氮和酸性洗涤纤维的含量,弗氏评分分别为70.33、74.33和67.67,进一步提高了青贮发酵品质。与对照相比,苯甲酸钠和丙酸添加组不同程度地增加了C18:2n6或C18:3n3的含量,而糖蜜添加组降低了C18:2n6和C18:3n3的含量(P<0.05)。综上所述,丙酸和苯甲酸钠适宜于作为青贮添加剂生产优质紫花苜蓿青贮饲料。

The objective of this study was to improve fermentation quality and inhibit the loss of unsaturated fatty acids from alfalfa silage.Alfalfa was ensiled without additives(control),or with sodium benzoate,sodium caseinate,hexadecanoic acid,molasses,or propionic acid.After ensiling for 65 days,the fermentation quality and fatty acid contents of the various silages were evaluated.For the control silage,the pH was lower than 4.50,the lactic acid content was 54.25 g∙kg^-1 DM,and the butyric acid content was lower than 5.00 g∙kg^-1 DM.The Flieg score of the control silage was 64.33,indicative of good fermentation quality.Compared with the alfalfa material before ensiling,the silages showed significantly increased contents of linoleic acid(C18:2n6)and linolenic acid(C18:3n3)(P<0.05).Compared with the control silage,silages fermented with hexadecanoic acid and sodium caseinate showed non-significant(P>0.05)and significant(P<0.05)reductions in lactic acid content,respectively;and silage fermented with sodium caseinate showed a significantly increased(P<0.05)butyric acid content.The silages fermented with hexadecanoic acid and sodium caseinate had Flieg scores lower than 50.00,indicative of poor fermentation quality.Compared with control silage,the silages fermented with sodium benzoate,propionic acid,and molasses showed increased lactic acid contents,decreased pH,and lower contents of ammonia nitrogen and acid detergent fiber.The Flieg scores were 70.33 for sodium benzoate-treated silage,74.33 for propionic acid-treated silage,and 67.67 for molasses-treated silage,indicative of better fermentation quality than that of the control.Compared with the control silage,silages fermented with sodium benzoate and propionic acid showed increased C18:2n6 or C18:3n3 contents,while silage fermented with molasses had decreased contents of C18:2n6 and C18:3n3(P<0.05).In summary,sodium benzoate and propionic acid are suitable additives to produce highquality alfalfa silage.