添加乙酸对西藏燕麦和紫花苜蓿混合青贮发酵品质和有氧稳定性的影响

摘要

The obj ective of this study was to evaluate the effects of adding acetic acid on the fermentation quali-ties and aerobic stability of mixed silage of oat and alfalfa.The treatments were as follows:control (CA)and three treatments of different acetic acid addition ratios (0 .3%,0 .4%,0 .5% of fresh weight ).These silos were opened 30,45 and 60 days after ensiling and the fermentation quality was analyzed.Then other silos were opened 60 days after ensiling and exposed to the air,and the aerobic stability was analyzed.Addition of acetic acid significantly (P<0.05)decreased the pH value of mixed silage,and the pH values of 0.4%and 0.5%ace-tic acid addition silages were significantly (P<0.05)lower than that of 0.3% acetic acid addition silages.Lac-tic acid (LA)contents of all acetic acid addition silages were significantly (P<0.05)higher than those of con-trol after 60 days from ensiling,however,there was no significant (P>0.05)difference among all acetic acid silages.Acetic acid addition significantly (P<0.05 )decreased the ratio of ammonia nitrogen/total nitrogen (AN/TN),and there was a pH decline (P>0.05)with increased of acetic acid addition.Water soluble carbo-hydrate (WSC)contents of all silages with acetic acid added were significantly (P<0.05)higher than those of the control,and 0.4% acetic acid addition silages showed the highest WSC content.During the first 10 days of aerobic exposure,the values of pH and AN/TN were stable in all silages,and those of silages with acetic acid added remained lower than these of control.After 10 days of aerobic exposure,the pH value of all silages in-creased,and that of the control significantly (P<0.05 )increased.The contents of LA and WSC decreased generally during the aerobic exposure process;all acetic-acid-treated silages showed significantly (P<0.05 ) higher LA and WSC than control,and the silage with 0.4% acetic acid added always had the highest lactic acid content.From the above results it is suggested that 0 .4% acetic acid addition is appropriate.%为探讨不同水平乙酸对燕麦和紫花苜蓿（7∶3）混合青贮发酵品质和有氧稳定性的影响，试验设对照组和3个乙酸添加组（0．3％，0．4％，0．5％），青贮后第30，45和60天开窖取样，测定青贮饲料的发酵品质，同时60 d后打开剩余的所有实验室青贮窖，将青贮饲料暴露于空气中，测定青贮饲料有氧稳定性。结果表明，添加乙酸显著（P＜0．05）降低了混合青贮饲料的pH，其中0．4％与0．5％乙酸处理组pH 显著（P＜0．05）低于0．3％乙酸处理组。青贮60 d后乙酸添加组乳酸含量显著（P＜0．05）高于对照组，但处理组间差异不显著（P＞0．05）。添加乙酸显著（P＜0．05）降低了青贮过程中氨态氮／总氮，且氨态氮／总氮随着乙酸添加量的增加呈下降趋势（P＞0．05）。各乙酸添加组水溶性碳水化合物均显著（P＜0．05）高于对照组，其中0．4％乙酸添加组最高。在有氧暴露前10 d，各组pH 和氨态氮／总氮基本保持稳定，其中乙酸添加组低于对照组。暴露10 d后各组pH 均有上升，其中对照组显著（P＜0．05）上升。在整个有氧暴露阶段，乳酸和水溶性碳水化合物含量逐渐下降，但各乙酸添加组均显著（P＜0．05）高于对照组，其中0．4％乙酸添加组乳酸含量始终保持最高。综合考虑发酵品质和有氧稳定性，0．4％乙酸添加量最适宜。