| Oat and common vetch which were cultivated in Tibet were choosed as fermented material. Oat and common vetch were ensiling at different rates and determined the quality of mixed silages. Selecting the best ensiling rate and then applying enhancers (malosses, lactic acid bacteria) and inhibitors (propionic acid, sorbic acid, ethanol) to further improve fermentation quality and aerobic stability of the mixed silage. So theoretical support and technical guidance of the mixed silage of oat and common vetch can be provided in Tibet.1. A study on fermentation quality of mixed silage of oat and common vetchThe treatments were as follow:(1) 100% oat; (2) 90% oat+10% common vetch; (3) 80% oat+20% common vetch; (4) 70% oat+30% common vetch,The result showed that pH value of all treatments are lower than 4.2. Treatment oat 100% and oat90% was significantly (P<0.05) lower than other treatments at 30 days,and there is not significantly among all treaterment after 45 days, lactic acid contents were increasing as the process of silage was prolonged. Oat70% was not significantly (P>0.05) or significantly higher (P<0.05) than other treatments. Ammonia nitrogen/total nitrogen ratio of oat 100% were lower than others.Treatment oat70% has better fermentation quality than other treatments. Oat and common vetch mixed at the rate of 7:3 has the best fermentation quality.2. The effect of adding molasses and lactic acid bacteria on the fermentation quality and aerobic stability of oat and common vetch mixed silageThe treatments as follows in this experiment:no additives(Control), lactic acid bacteria(L) and molasses(M). The results showed that adding of L, M and S were efficient in improving the fermentation quality of mixed silages compared with the control. There were significantly (P<0.05) higher lactic acid content, lactic acid/acetic acid values in the M and L addition as compared with control, while the pH values, acetic acid, total volatile fatty acid content and ammonia nitrogen/total nitrogen values of silages was significantly (P<0.05) lower than other control.During the whole aerobic exposure period, comparing with the control, the pH value, ammonia nitrogen/total nitrogen ratio and volatile fatty acid contents were lower, lactic acid content was higher, delayed the time of deterioration of mixed silage. That adding molasses and lactic acid bacteria have some help on aerobic stability of mixed silage, consistent with their effects of fermentation quality.3. The effect of adding propionic acid, ethanol and potassium sorbate on the fermentation quality and aerobic stability of oat and common vetch mixed silageThe treatments as follows in this experiment:no additive (Control), propionic acid (B), potassium sorbate (S) and ethanol (Y). The result showed that dry matter contents of each treatments were not significant different (P>0.05), the lactic acid contents and lactic acid/acetic acid ratio of potassium sorbate and ethanol treatment were significantly (P<0.05) higher than that of the control and propionic acid treatment. The ammonia nitrogen/total nitrogen ratio of potassium sorbate treatment was significantly (P<0.05) higher than the control,while there was no sgnificant (P>0.05) diference between ethanol and other treatments. Thus,effect of additives on the fermentation quality of mixed silage was potassium sorbate> ethanol> propionic acid.During the whole aerobic exposure period, with the time of aerobic exposure, the pH value decreased gradully, lactic acid contents increased gradully, ammonia nitrogen/total nitrogen ratio increased slowly in the treated silage as compared with the control silage, and pH value, ammonia nitrogen/total nitrogen ratio and lactic acid contents of propionic acid treatment is the lowest, pH value and lactic acid contents of potassium sorbate and ethanol treatment was not significantly different (P>0.05), but the ammonia nitrogen/total nitrogen ratio of ethanol treatment was significantly (P<0.05) higher than the potassium sorbate treatment. Effect of additives on the aerobic stability of mixed silage was as follows: propionic acid> ethanol> potassium sorbate.4.1 Effect of combining addition of propionic acid,ethanol,potassium sorbate with molasses on fermentation quality and aerobic stability of oat and common vetch mixed silageThe treatments as follows in this experiment:(1) no additive (Control); (2) 0.4%propionic acid+3%molasses (BM); (3) 0.15% potassium sorbate+3%molasses (SM); (4) 3.5%ethanol+3%mollases (YM). The result showed that all mixed silages treated with additives significantly decreased pH value, ammonia nitrogen/total nitrogen ratio and total volatile fatty acids contents, significantly (P<0.05) increased lactic acid content and lactic acid/acetic acid ratio. Adding additives effectively improved the fermentation quality of oat and common vetch mixed silage, effect of additives on the fermentation quality of mixed silage was propionic acid+molasses> potassium sorbate+molasses> ethanol+molasses.During the whole aerobic exposure period, silages treated with additives decreased pH value as compared with the control silage. With the time of aerobic exposure, the lactic acid content of silage treated with SM increased gradually, the lactic acid contents of silage treated with YM and BM decreased gradually, while they were higher than the control silage. The ammonia nitrogen/total nitrogen ratio of silage treated with BM and SM increased gradually. Although the ammonia nitrogen/total nitrogen ratio of silage treated with YM increased, it did not change significantly (P>0.05). The ammonia nitrogen/total nitrogen ratios of silages treated with additives were all significantly (P<0.05) lower than control. Thus, that adding additives could improve aerobic stability of oat and common vetch mixed silage, effect of additives on the aerobic stability of mixed silage was as follows:propionic acid+molasses> potassium sorbate+molasses> ethanol+molasses.4.2 Effect of combining addition of propionic acid, ethanol, potassium sorbate with lactic acid bacteria on fermentation quality and aerobic stability of oat and common vetch mixed silageThe treatments as follows in this experiment:(1) no additive (Control); (2) 0.4%propionic acid+lactic acid bacteria (BL); (3) 0.15% potassium sorbate+lactic acid bacteria (SL); (4) 3.5%ethanol+lactic acid bacteria (YL). The result showed that all mixed silages treated with additives significantly (P<0.05) decreased pH value,ammonia nitrogen/total nitrogen ratio and total volatile fatty acids contents, significantly (P<0.05) increased lactic acid content and lactic acid/acetic acid ratio. Adding additives effectively improved the fermentation quality of oat and common vetch mixed silage,effect of additives on the fermentation quality of mixed silage was propionic acid+lactic acid bacteria> potassium sorbate+lactic acid bacteria> ethanol+lactic acid bacteria.During the whole aerobic exposure period, with the time of aerobic exposure, pH value of the control silage and silages treated with BL and YL increased, pH of silage treated with SL decreased gradually. While the pH of silage treated with BL and YL was significantly (P<0.05) lower than the control silage and SL silage was the lowest. The lactic acid contents of silages treated with significantly (P<0.05) higher than the control silage, with the time of aerobic exposure, the lactic acid content of silage treated with SL increased gradually,the lactic acid contents of silages treated with BL and YL decreased gradually.The ammonia nitrogen/total nitrogen ratios of silages treated with additives were all significantly (P<0.05) lower than the control silage. Thus, that adding additives could improve aerobic stability of oat and common vetch mixed silage and prevent it from aerobic spoilage. Effect of additives on the aerobic stability of mixed silage was as follows: propionic acid+lactic acid bacteria> potassium sorbate+lactic acid bacteria> ethanol+ lactic acid bacteria. |
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