添加糖蜜和乙酸对西藏发酵全混合日粮青贮发酵品质及有氧稳定性影响

为研究乙酸和糖蜜对发酵全混合日粮(FTMR)品质及有氧稳定性的影响,试验以全混合日粮(TMR)为发酵原料,设对照组、乙酸(A)、糖蜜(M)、乙酸和糖蜜组合添加(AM)4个处理,发酵45 d后分析FTMR的发酵品质,同时将所有FTMR暴露到空气中,分别在第6,9和12天取样评定其有氧稳定性。结果表明,与对照相比,A和AM组降低了乳酸含量(P>0.05),各组仅检测到微量的丙酸、少量的丁酸和较低的氨态氮/总氮,表明各组FTMR发酵品质均良好。有氧暴露6 d后,各组乳酸、乙酸和水溶性碳水化合物含量均呈不同程度的下降,对照和M组pH值在第12 天显著(P<0.05)上升至5.70和6.50,具有较高的氨态氮/总氮和酵母菌数量。而A和AM组乳酸含量均呈先上升后下降的变化趋势,且好氧性微生物和酵母菌数量在整个有氧暴露的过程中始终维持在较低水平,有氧暴露12 d后pH值仍维持在4.50左右,延长了有氧稳定时间。综合考虑,为了获得品质优良的FTMR饲料,可在TMR中添加0.3%乙酸,既不影响发酵品质,也可提高其有氧稳定性。

Effects of molasses and acetic acid on fermentation and aerobic stability of total mixed ration silage in Tibet

An experiment was undertaken to study the effects of acetic acid or/and molasses on the quality of fermented total mixed ration silage. Treatments: silage fermented without additive (control), with acetic acid (0.3% fresh matter basis), with molasses (3% fresh matter basis), or with acetic acid+molasses. There were 20 silos per treatment. All silos were opened 45 d after ensiling; five silos per treatment were analysed to determine fermentation characteristics, the remaining silos were exposed to air for 12 d to evaluate aerobic stability. After 45 dall silages were of good quality having high lactic acid concentration, low ammonia/total nitrogen, low butyric acid and very little propionic acid. During aerobic exposure, lactic acid, acetic acid and water soluble carbohydrate tended to decrease in all silages. The pH of the control and molasses treated silages increased significantly to 5.70 and 6.50 respectively and ammonia/total nitrogen and yeast counts were higher than the acetic acid and acetic acid+molasses treatments after 12 days of exposure. However, adding acetic acid reduced ammonia/total nitrogen compared with the control. Lactic acid content in the acetic acid and acetic acid+molasses silages increased during the early stages of aerobic exposure and then slowly decreased. Undesirable bacteria and yeast counts in the acetic acid treatment remained at low levels during aerobic exposure and the pH remained at about 4.50. It is concluded that adding 0.3% acetic acid maintained fermentation quality and improved the aerobic stability of fermented total mixed ration silage.