添加乳酸菌和发酵底物对桑叶青贮发酵品质的影响

摘要

This study was conducted to assess the use of mulberry leaves as a non-conventional forage resource. The effects of lactic acid bacteria,glucose and molasses on fermentation and quality of mulberry leaf silage were determined.In addition to a control group (C),mulberry leaves were treated with glucose (G),molasses (M),Lactobacillus plantarum (P),L.plantarum+glucose (P+G)and L.plantarum+molasses (P+M). Both control and treatment groups were ensiled in laboratory silos,and samples taken at 7,14,30 and 60 days after initiation of ensiling.The results revealed that addition of L.plantarum accelerated lactic acid fermenta-tion.After 7 days of ensiling the lactic acid content in P,P+G and P+M treatments were >6 times that of the control.The pH of all treatments including L.plantarum fell below 4.3;the pH of P+G and P+M fell to a-bout 4.0 after 60 days.Addition of glucose or molasses did not improve fermentation quality.The pH of C,G and M were still above 5.85 after 30 days.At the end of ensiling,the pH of C,G and M treatments decreased to 5.96,5.35 and 5.24,respectively,significantly (P <0.05)higher than that in P.The acetic acid contents in P was the highest among all silages,significantly higher than that of C,G and M during the whole ensiling pe-riod (P <0.05),significantly higher than that of P+G and P+M after 7 days ensiling (P <0.05).The ammo-nia nitrogen:total nitrogen ratio (AN:TN)in P was significantly lower than that in control after 7 days (P <0.05).Afterwards,the AN:TN increased steadily in all silages while AN:TN in P,P+G and P+M was sig-nificantly lower than that in C,G and M until the end of the ensiling period.It was concluded that addition of L.plantarum markedly improved fermentation quality of mulberry leaves,while the addition of L.plantarum with as glucose and molasses did not further improve fermentation quality.%为开发桑叶作为非常规饲料资源，本试验探讨了添加乳酸菌、葡萄糖或糖蜜对桑叶青贮发酵品质的影响，试验设对照组（C）、乳酸菌组（P）、葡萄糖组（G）、糖蜜组（M）、乳酸菌＋葡萄糖组（P＋G）、乳酸菌＋糖蜜组（P＋M），青贮后第7，14，30和60天开窖取样分析桑叶青贮饲料发酵品质。结果表明，添加乳酸菌加速了桑叶青贮过程中乳酸发酵，青贮第7天 P，P＋G 和 P＋M 组乳酸含量已达到 C 组的6倍以上，pH 值降至4．30以下，其中 P＋G 和P＋M在青贮结束时降至4．0左右。补充发酵底物并未有效改善桑叶青贮发酵品质，C、G 和 M 组 pH 值在青贮前30 d 始终保持在5．85以上，青贮60 d 时 C 组为5．96，G 和 M 组分别下降至5．35和5．24，显著（P ＜0．05）高于 P组。整个青贮过程中 P 组显示最高的乙酸含量，始终显著（P ＜0．05）高于 C、G 和 M 组，青贮7 d 后开始显著（P ＜0．05）高于 P＋G 和 P＋M 组。青贮第7天 P 组氨态氮／总氮显著（P ＜0．05）低于对照组，之后各组氨态氮／总氮均随青贮时间的延长逐渐上升，其中 P、P＋G 和 P＋M 组氨态氮／总氮显著（P ＜0．05）低于 C、G 或 M 组直至青贮结束。本试验结论认为单独添加乳酸菌明显提高了桑叶青贮发酵品质，而组合添加并未进一步得到大的改善。