Effect Of Adding Sorbic Acid And Ethanol On The Fermentation Quality Of Napier Grass And Hybrid Pennisetum Silage

There were four experiments were carried out in this study, and this study was to evaluate the effects of adding sorbic acid or ethanol on the fermentation quality and residual WSC contents of Napier grass(Pennisetum purpureum Schumach) and Hybrid pennisetum(Pennisetum americanum×P. purpureum) silages.Experiment Ⅰ. Effect of adding sorbic acid on the fermentation quality of Napier grass silage during ensilingThe silage treatments were as follows:control:without additive. sorbic acid treatment: Napier grass was treated with0.1%sorbic acid on the fresh weight basis. All silos were kept at the ambient temperature, and the silos were opened after0.5,1,1.5,2,3,5,7,14and30days of ensiling and the fermentation quality was analyzed. The contents of DM and WSC and the values of pH and LA/AA of0.1%S were higher than control, however, LA content did not greatly change within initial fermentation stage.0.1%S showed a significantly (p<0.05) lower AA and T-VFAs contents and AN/TN value as compared with the control. These suggested that the sorbic acid was effective on inhibiting the proteolysis and the use of WSC by aerobic microorganisms in the early stage of ensiling, thereby decreased the loss of WSC. However, sorbic acid also inhibited lactic acid bacteria activity in the early stage of ensiling. There was a significantly (p<0.05) higher WSC, or higher (p>0.05)DM and LA contents than control, however, had lower AN/TN value after3days of ensiling. At the later stage of ensiling, sorbic acid stimulated the activity of LAB and effectively inhibited the use of protein and WSC by clostridia and other undesirable microorganisms activities during ensiling, thereby decreased the loss of WSC and protein.0.1%S addition saved the fermentation substrate for lactic acid fermentation and improved the silage quality in this experiment. Experiment II. Effect of adding ethanol on the fermentation quality of Napier grass silage during ensilingThe silage treatments were as follows:control:without additives, ethanol treatment: Napier grass was treated with2.5%ethanol on the fresh weight basis. All silos were kept at the ambient temperature, and the silos were opened after0.5,1,1.5,2,3,5,7,14and30days of ensiling and the fermentation quality was analyzed. Compared with the control,2.5%E significantly (p<0.05) increased DM content and slightly (p>0.05) increased the WSC content and pH value. LA content of2.5%E was lower than control, whereas significantly (p<0.05) decreased the value of AN/TN and the contents of AA and T-VFAs during the early stage of fermentation.These suggested that the sorbic acid was effective on inhibiting the use of protein and WSC by aerobic microorganisms during the initial fermentation stage and reduced the silage losses. However, ethanol also inhibited lactic acid bacteria activity in the early stage of ensiling. After5days of ensiling,2.5%E showed a significantly (p<0.05) higher LA content, and showed a small (p>0.05) increase in DM, WSC contents and LA/AA value.2.5%E significantly (p<0.05) decreased AN/TN and slightly (p>0.05) decreased PA and BA contents. The value of pH and the contents of AA, T-VFAs were lower (p>0.05) and significantly (p<0.05) lower as compared with control. These suggested that the ethanol was effective on inhibiting the proteolysis and the use of WSC by the clostridia and other undesirable microorganisms activities during the fermentation process, and reduced the silage losses. These indicated that2.5%E stimulated homo-fermentative lactic acid bacteria activity, greatly increased the efficiency of WSC utilization by LAB, and further improved the fermentation quality.Experiment Ⅲ. Effect of adding sorbic acid on the fermentation quality of Hybrid pennisetum silage during ensilingThe silage treatments were as follows:control:without additive, sorbic acid treatment:Napier grass was treated with0.1%sorbic acid on the fresh weight basis. All silos were kept at the ambient temperature, and the silos were opened after0.5,1,2,3,5,7,14and30days of ensiling and the fermentation quality was analyzed. There is no significant (p>0.05) difference in LA content and pH value of silage with0.1%S compared with the control during the initial fermentation stage.0.1%S significantly (p<0.05) decreased the contents of AA, BA and T-VFAs, however, significantly (p<0.05) increased the DM and WSC contents compared with the control in the early stage of ensiling. These suggested that the sorbic acid was effective on inhibiting the proteolysis and the use of WSC by aerobic microorganisms in the early stage of ensiling, thereby decreased the loss of WSC. In the later stage of ensiling (after5days of ensiling), LA content of0.1%S increased quickly and was higher than control in the end of ensiling.0.1%S significantly (p<0.05) increased DM and WSC contents, and slightly (p>0.05) increased LA/AA but decreased the contents of BA, T-VFAs contents. And pH value and AA, PA contents of0.1%S were lower (p>0.05) and significantly (p<0.05) lower than control. The value of AN/TN of0.1%S was lower (p<0.05) than control during the whole fermentation process. Based on the results, addition0.1%S did not inhibit the activity of LAB in the later stage of ensiling, but was effective on inhibiting the use of protein and WSC by clostridia and other undesirable microorganisms activities, thereby decreased the loss of WSC and protein, and saved WSC for lactic acid fermentation and improved the fermentation quality of Hybrid pennisetum silage.Experiment Ⅳ. Effect of adding ethanol on the fermentation quality of Hybrid pennisetum silage during ensilingThe silage treatments were as follows,control:without additives; ethanol treatment: Napier grass was treated with2.5%ethanol on the fresh weight basis.All silos were kept at the ambient temperature, and the silos were opened after0.5,1,2,3,5,7,14and30days of ensiling and the fermentation quality was analyzed. Except0.5and5d, the WSC content of the silage with2.5%E was significantly (p<0.05) higher than control during the ensiling. In the early stage of ensiling,2.5%E showed a slight increase in the content of DM and value of pH. And the LA, AA, BA, T-VFAs contents and AN/TN value of2.5%E were lower (p<0.05) than control. These suggested that the2.5%ethanol was effective on inhibiting the proteolysis and the use of WSC by aerobic microorganisms in the early stage of ensiling, thereby decreased the loss of WSC. In the later stage of ensiling,2.5%E showed a tendency of increase in DM, LA, BA contents and LA/AA value and decrease in the values of pH, AN/TN and the contents of AA, PA and T-VFAs as compared with the control. There suggested that2.5%ethanol did not completely inhibited the use of protein and WSC by clostridia and other undesirable microorganisms activities, producing less LA content, and pH did not quickly decrease to below4.2, and produced more BA and AN contents.