| The Tibetan plateau is regarded as the Earth’s third pole and the highest unique territorial unit in the world, thus, its climate and natural environment are inherently extreme and instable. The cold and arid continental climates and short growing seasons are considered to be the most important limiting factors for forage production. Straw could be ensilaged and used as livestock’s feed. Research has indicated that lactate acid bacteria inoculation greatly increases the fermentation quality of silage, improve the nutritive value and positively promote livestock performance. This experiment was carried out in order to isolate and identify lactate acid bacteria strains which are suitable for silage additives. The chosen strains were isolated from silage made in Tibet without any additives. These were identified by physiological and biochemical ways. The16S rRNA analysis was done to investigate the optimal fermentation condition. After this method, the chosen lactate acid bacteria were inoculated as silage additives into forage grass in order to investigate the influence of the additives on the fermentation quality of silage and rumen. The in vitro dry matter digestibility was also carried out to investigate the influence of silage which has been inoculated with lactate acid bacteria or not with silages on milk yield and composition. The experiment was divided into five parts:1Screening and identification of Lactic Acid BacteriaThe study was carried out in order to screen and identify lactic acid bacteria strains which are suitable for silage additives. The chosen strains were isolated from maize straw silage made in Tibet without any additives. These were identified by physiological, biochemical, and16S rRNA analyses. In the process, the methodology used led to us to obtain37strains from silage using MRS medium and GYP medium.8strains were also obtained after preliminary identification following physiological and biochemical methods. In the experiment, cluster analysis was carried out to determine acid production efficiency. The results were that2strains namely TBT608and TBT717were obtained and to be specific, TBT7’17was Lactobacillus plantarum while TBT608was Enterococcus faecalis.2Fermentation condition optimization of Lactic Acid BacteriaThis experiment was carried out in order to investigate the optimal sources of carbon, and nitrogen for the two species of bacteria namely TBT717and TBT608. The critical medium components and culture condition of these two species through the single factor experiments and orthogonal test were also used. The single factor analysis method was used to screen carbon source of cane sugar, glucose and maltose. Here we found out that the optimal carbon source of TBT717and TBT608was glucose. We used a single factor analysis method to screen the source of nitrogen, peptone, yeast powder and maize steep liquor powder. It was found out that the optimal nitrogen source of TBT717and TBT608was peptone together with yeast powder. It was further discovered that the optimal culture conditions for TBT717was30℃while inoculum size was2%and the pH6.2. The optimal culture conditions of TBT608was recorded and found out to be37℃while the inoculum size was2%and pH6.4. The carbon and nitrogen sources were evaluated through4-factor and3-level orthogonal tests. This was done to optimize the fermentation medium of the two bacteria species. Here the findings for the optimal fermentation medium of TBT717were as follows:glucose1.8%, peptone1.2%, yeast powder1.8%, K2HPO40.3%, tween-800.10%, MgSO4·7H2O0.058%, MnSO4-4H2O0.025%. As for the optimal fermentation medium of TBT606results were as follows:glucose2.0%, peptone2.0%, yeast powder1.8%, K2HPO40.2%, tween-800.10%, MgSO4·7H2O0.058%, MnSO4-4H2O0.025%. In this study, the period for collection of TBT717was16hours after culture while the collection time for TBT608was12hour after culture.3Effect of lactic acid bacteria on fermentation quality of silagesIn this experiment, the effect of lactic acid bacteria (Enterococcus faecalis and Lactobacillus plantram) on the changes of fermentation and fermentation quality of silages was investigated. There are two parts in this chapter. Part1is where maize stover was ensiled with Perennial ryegrass, Tall fescue, Hullessbarley straw, Common Vetch, Wheat straw or Alfalfa in1L laboratory silao. There were two treatments in each experiment which were control group and LAB inoculant treatment group. The silos were opened after15,30and45days of ensiling respectively. The fermentation quality was analyzed in both groups. The results were that in maize silage mixed with various components and other materials showed higher fermentation efficiency and nutrition components. In that case LAB inoculants improved the fermentation quality which was indicated by higher LA contents while the LA/AA levels and AA and VFAs contents were low. LAB inoculants inhibited the BA and AN production during the ensiling, and there were evidence of presence of LAB inoculants in silages. In part2maize stover was ensiled in silos, which were opened after150days and then ensiling and the fermentation quality were both analyzed. It was found out that LAB inoculants did not only increased the DM, LA and CP content, but also significantly decreased AA content, pH value and AN/TN as compared with control. Traces of PA were found in LAB inoculated silage while there were no BA content in it. This can be explained in the way that may be both Enterococcus faecalis and Lactobacillus plantram were homofermentative bacteria, whose fermentation efficiency was higher than heterofermentative bacterial. It was observed that during the early stage of ensiling process more LA production and pH Value sharply declined which is suspected to inhibit the activities of aerobic microorganism which included acetic acid bacterial production. In this study, it can be concluded that inoculation with Enterococcus faecalis and Lactobacillus plantram was the effective way for improving the fermentatation process and quality of maize straw silage.4Effect of maize straw silages fermentation characters inoculated with rumen fluid in vitroThe study was carried out to evaluate the effect of fermentation characters of maize straw silages and the silage dry matter digestibility in vitro. In this experiment, in vitro dry matter digestibility (IVDMD) was determined through fermentation, inoculated with rumen fluid of wethers, in various combinations with soluble starch. The soluble starch represented a concentrate feed, silage represented feeding sole roughage. The IVDMD was determined at24h and48h after incubation. Silage without inoculated LAB served as control for each feed combination. The results indicate that, LAB applied at ensiling increased the IVDMD of the maize straw silage. And the LAB inoculated silages showed suitable pH value for rumen bacteria and lower ratio of Acetic/propionic acid. These results confirmed that application of the complex lactic acid bacteria improved fermentation quality and in vitro dry matter digestibility of the maize straw silage.5Effects of maize straw silages on dairy cows lactational performance and milk qualityIn the experiment, a total of20Holstein dairy cows with the parity of2.56±0.3, body weight of590kg±18kg and a daily milk production of20.07kg±2.39kg/d have been divided into two groups by randomized block design method. The pretesting time was10days while the testing time was30days. At the start and the end of the testing time, data has been collected for milk yield and analyzed. This experiment was carried out to study the influence of milk yield and milk component produced by cows fed with maize straw silage which has been inoculated with lactate acid bacteria or silage without lactate acid bacteria. The results were that the cows fed with silage inoculated with lactase acid bacteria increased in milk yield with high butterfat content, lactoprotein content, unlipoid milk solids content and production in some levels(P>0.05). In this experiment generally the conclusion was that feeding cows with maize straw silage inoculated with lactase acid bacteria shows some levels of improvement in milk yield and quality as compared with cows which were fed with silage without lactase acid bacteria. |
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