| The purpose of this study was to make full use of forage resource in Tibetan rural areas and to meet the forage need of herbivores during winter and spring. The fermentation quality of mixed silages of oat (Avena sativa L) and alfalfa (Medicago sativa L) with different proportion were investigated. The oat and alfalfa were cultivated in the experimental field of the Grassland Station of Gongga, Shannan prefecture of Tibet. The suitable ration of mixture was screened for further study firstly, and then effects of adding molasses, lactic acid bacteria, propionic acid, potassium sorbate and ethanol on fermentation quality and aerobic stability of mixed silage were studyed. The significance of this study was to provide a theoretical support for high quality silage modulation. The study was divided into the following three parts.1. Effects of different mixed ratio of oat and alfalfa on fermentation qualityThis study compared the fermentation qualitys of mixed silages of oat and alfalfa in different proportions as follows:100% oat (Oat100%),90% oat+10% alfalfa (Oat 90%), 80% oat+20% alfalfa (Oat 80%),70% oat+30% alfalfa (Oat70%). The results showed that the pH values of all silages were maintained at about 4.10. The contents of lactic acid and crude protein increased significantly (P<0.05) with the increase of alfalfa percentage in mixed silages. However, the ratios of ammonia nitrogen/total nitrogen (AN/TN) in all mixed silages (>90 g·kg-1 TN) was higher than the control after 60 days ensiling. It was concluded that mixed oat silage inclusion with 30% alfalfa had the best fermentation quality in all silages.2. Effects of additives on fermentation quality and aerobic stability of mixed silages of oat and alfalfa (70% oat:30% alfalfa)2.1 Effects of molasses or lactic acid bacteria on fermentation quality and aerobic stability of mixed silages of oat and alfalfaTo evaluate the effects of adding molasses or LAB on fermentation quality and aerobic stability of mixed silages of oat and alfalfa, the treatments were designed as follows: Control (C),4% molasses (M), and 0.6ml lactic acid bacterial suspension (LAB). Research had revealed that both molasses and LAB treatments showed significantly(P<0.05) higher lactic acid and, lactic acid/aectic acid and lower AN/TN than the control, and had better fermentation quality. After aerobic exposure of 15 days, the pH of molasses addition reached 4.88, and the AN/TN ran up to 119.07 g·kg-1 TN. During aerobic exposure, the pH of LAB treatment increased more slowly than the control and the M treatment. LAB addition silage keep always high lactic acid and low AN/TN during aerobic process and had better aerobic stability.2.2 Effects of propionic acid, potassium sorbate or ethanol on fermentation quality and aerobic stability of mixed silages of oat and alfalfaTo evaluate the effects of adding propionic acid, potassium sorbate and ethanol on fermentation quality and aerobic stability of mixed silage of oat and alfalfa, the treatments were as follows:control (C),0.4% propionic acid (B),0.15% potassium sorbate (S) and 3.5% ethanol (Y). Propionic acid addition decreased pH and AN/TN, and had no effect on the content of lactic acid. Propionic acid addition had significantly (P<0.05) higher contents of propionic acid and total VFAs than the control. Compared with the control, potassium sorbate addition had no significant effects on pH, dry matter, lactic acid, or acetic acid during ensiling. Ethanol addition enhanced lactic acid production, decreased pH and AN/TN, and significantly (P<0.05) increased residual WSC contents. During aerobic exposure, the pH and AN/TN of all additive treatments increased more slowly than the control. Additives treatments had better aerobic stability.3. Effects of combined additives on fermentation quality and aerobic stability of mixed silage of oat and alfalfa3.1 Effects of propionic acid and molasses or LAB combination on fermentation quality and aerobic stability of mixed silage of oat and alfalfaTo evaluate the effects of adding propionic acid and molasses or LAB combination on fermentation quality and aerobic stability of mixed silages of oat and alfalfa, the treatments were designed as follows:control (C),0.4% propionic acid (B),0.4% propionic acid+4% molasses (B+M) and 0.4% propionic acid+0.6ml lactic acid bacterial suspension (B+L). The results showed that the B+M and B+L treatments had significantly (P<0.05) lower pH and AN/TN than the control, and had significantly (P<0.05) higher lactic acid content and lactic acid/acetic acid than the B treatment. After 15 days aerobic exposure, the pH and AN/TN of all addition treatments were significantly (P<0.05) lower than the control (pH: 4.81, AN/TN:123.66 g·kg-1 TN). The lactic acid and WSC contents of addition treatments were significantly (P<0.05) higher than the control. And the addition treatments had better aerobic stability.3.2 Effects of potassium sorbate and molasses or lactic acid bacteria combination on fermentation quality and aerobic stability of mixed silage of oat and alfalfaThe aim to this study was estimating effects of adding potassium sorbate and molasses or LAB combination on fermentation quality and aerobic stability of mixed silages of oat and alfalfa. The treatments were as follows:control (C),0.15% potassium sorbate (S), 0.15% potassium sorbate+4% molasses (S+M) and 0.15% potassium sorbate+0.6ml lactic acid bacterial suspension (S+L). Based on results, the S+M and S+L silages has significantly higher lactic acid and WSC contents than the control and the S silage. During aerobic exposure, potassium sorbate could play a role in inhibition of yeast and fungi, so all addition silages showed better aerobic stability. However, the S+M silage had more residual WSC. The aerobic stability of S+M was not as good as S+L silage. It was concluded that potassium sorbate and LAB combination was effective for improving the fermentation quality and aerobic stability. 3.3 Effects of ethanol acid and molasses or lactic acid bacteria combination onfermentation quality and aerobic stability of mixed silage of oat and alfalfaIn order to assessing effects of adding ethanol and molasses or LAB combination on fermentation quality and aerobic stability of mixed silages of oat and alfalfa in this study, the treatments were designed as follows:control (C),3.5% ethanol (Y),3.5% ethanol+4% molasses (Y+M) and3.5% ethanol+0.6ml lactic acid bacterial suspension (Y+L). The results were as follows:all addition treatments had significantly (P<0.05) higher lactic acid and WSC contents. And the pH and AN/TN decreased significantly (P<0.05) than the control. Compared with ethanol alone, Y+M and Y+L silages has higher lactic acid content. During aerobic exposure, pH and AN/TN of all additive treatments increased slowly. After aerobic exposure of 15 days, pH and AN/TN of all additive treatments were significantly (P <0.05) lower than the control, and the lactic acid were significantly (P<0.05) higher than the control. Overall consideration, either ethanol alone or ethanol and molasses or lactic acid bacteria combination were effective for improving the fermentation quality and aerobic stability. |
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