添加乙醇和糖蜜对西藏地区燕麦和紫花苜蓿混合青贮发酵品质的影响

Effect of Adding Ethanol and Molasses on Fermentation Quality of Mixed Silage of Oat and Alfalfa in Tibet

为了充分利用西藏农区饲草资源,满足草食动物冬春季节的饲草料需求,本试验首先比较了不同比例燕麦和紫花苜蓿混合青贮的发酵品质,结果表明,各混贮组青贮饲料的pH均保持在4.10左右,乳酸含量随着紫花苜蓿添加比例的增加而上升,虽然随着紫花苜蓿混合比例的增加粗蛋白含量显著增加(P<0.05),但各混贮组显示较高的氨态氮/总氮值,均高于90g·kg-1 TN。为了进一步改善青贮饲料发酵品质,抑制青贮过程中粗蛋白的降解,选择燕麦和紫花苜蓿以7∶3混合,并分别添加4%糖蜜、3.5%乙醇及其组合。结果显示,糖蜜和乙醇单独添加组发酵品质均良好,糖蜜添加组显示最高的乳酸含量和最低的pH,与对照组相比,单独添加糖蜜显著降低了乙酸含量和氨态氮/总氮值。单独添加乙醇显著提高了乳酸含量,降低了丙酸含量、pH和氨态氮/总氮值,显著提高了水溶性碳水化合物含量。但与单独添加乙醇或糖蜜相比,乙醇和糖蜜组合添加对青贮发酵品质的改善效果不显著,因此综合考虑,在燕麦和紫花苜蓿以7∶3混合青贮的基础上单独添加4%糖蜜或3.5%乙醇即可获得优质青贮饲料。

The objective of this study was to improve the utilization efficiency of forage resources in Tibetan rural areas and to meet the forage need of herbivores during winter and spring.The fermentation quality of mixed silages of oat and alfalfa were investigated firstly.The results showed that the pH of all silages were maintained at about 4.10,the content of lactic acid increased with the increase of alfalfa percentage in mixed silages.Although the crude protein content increased significantly(P<0.05)with increasing proportion of alfalfa,the ratios of Ammonia /total nitrogen(AN/TN)in all mixed silages were more than 90g·kg-1 TN.In order to further improve the fermentation quality of mixed silage and inhibit degradation of crude protein during the ensiling process,mixed silage inclusion with 30%alfalfa was ensiled with 4% molasses,3.5% ethanol or the combination of molasses and ethanol,respectively.Molasses addition silages showedhighest lactic acid content and the lowest pH value.Compared with the control,molasses addition significantly decreased acetic acid content and the value of AN/TN.Ethanol addition enhanced lactic acid production,decreased the propionic acid content and the pH and AN/TN,and significantly increased residual water souble carbohydrate(WSC)content.Compared with the molasses or ethanol alone addition silages,the combination of molasses and ethanol did not significantly improve fermentation quality of mixed silages.It was concluded that the addition of 4% molasses or 3.5%ethanol were effective and economical for improving the fermentation quality of oat silages inclusion with 30%alfalfa.