| This work was conducted in 2013 and 2014 to investigate the ensiling techniques of making high-quality alfalfa silage and to compare the effectiveness of different additives for preserving alfalfa silage in farm-scale silos. Additionally, the nutritive value evaluation was studied. The work is primarily divided into the following four parts:Experiment Ⅰ : The effect of wilting and different additives on alfalfa silage fermentation and nutritive value were studied under laboratory conditions according to two factorial(2×7) randomized design. Lucerne(at the early bloom stage of maturity), wilted for 3 and 12 h respectively, was ensiled at 72.6% and 61.8% moisture contents. Chopped grasses at each moisture content were either untreated(CK) or treated with(1) inoculant(LAB);(2) sugar beet pulp(SB);(3) sodium formate(SF);(4) a combination of inoculant and sugar beet pulp(LAB+SB), and(5) sodium formate and sugar beet pulp combined(SF+SB). Forages were packed into triplicate 1-L laboratory silos per treatment at a density of 650 g/L. Silos were opened and analysed after 65 d of ensiling. The results showed that in low wilted treatments all treatments had lower p H and lower concentrations of acetic acid than did untreated silages(P<0.05). The higher lactic to acetic acid ratio was found in LAB and LAB+M-treated silages compared with untreated silage(P<0.05). The fermentation quality of treated silages were strengthened in low wilted treatments and these effects were stronger in the LAB+M-treated silage. In high wilted silages all treatments had higher lactic to acetic acid ratio but lower ammonia-N(% of TN) contents compared with control(P<0.05). A lower p H value was observed in LAB-treated silage among treatments(P<0.05). The application of LAB, LAB+SB and SF+SB did improve high wilted alfalfa silage fermentation compared with other treatments. Treated silages had a similar concentrations of neutral detergent fiber(NDF), acid detergent fiber(ADF), dry matter recovery ratio and 24 h rumen DM degradation compared with untreated silage at two wilted treatments. Furthermore, water-soluble carbohydrate concentrations were found increased in silage from alfalfa herbage treated with LAB+SB and SF-treated silage compared with untreated silage(P<0.05). Wilting reduced the rate of decline of silage p H(P<0.05) and produced silages with lower acetic acid(P<0.05) and ammonia-N contents(P<0.05) but higher dry matter, crude protein and water-soluable carbohydtate concentrations. In a conclusion, as silage wilting was increased(moisture content reduced from 72.6% to 61.8%) silage quality was improved. Inoculant and sugar beet pulp combined(LAB+SB) was found to be the most effective additive.Experiment Ⅱ: The effect of different additives on the fermentation, nutritive value and aerobic stability of alfalfa herbage(Medicago sativa L) were studied under farm-scale silos according to single factorial randomized design. Whole fourth-cut alfalfa was harvested at the early bloom stage of maturity and allowed to wilt to a moisture content of about 50%. Chopped grasses were untreated or after the following treatments: 1) control(no additives,CK); 2) Lactic acid bacteria(a commercial inoculant)(LAB) at 2×105 colony-forming units(CFU)/g of fresh forage; 3) a combination of lactic acid bacteria at 2×105 CFU/g of fresh forage and molasses at 2% of fresh forage weight(LAB+M) and 4) sodium dehydroacetate(SD) at 0.1% of fresh forage weight. Silages were sampled on d 90 after ensiling for fermentation and chemical analysis. At the end of the ensiling period, 90 d, the silages were subjected to an aerobic stability test. In this test, temperature variation was measured and served as spoilage indicators. The results showed that all silages have a good fermentation quality. The application of LAB, LAB+M and SD as silage additives could significantly increase the lactic acid, lactic acid to acetic acid ratio, dry matter recovery ratio and decrease ammonia-N(% of TN) contents(P<0.05) but did not alter the crude protein, neutral detergent fiber, Acid detergent fiber and water soluble carbohydrates compared with control(P>0.05). The SD silages had less lactic acid concentrations compared with LAB+M silages(P<0.05) and greater ammonia-N(of % TN) and p H value compared with the LAB and LAB+M silages(P<0.05), implied a relatively lower fermentation quality. The LAB silages and LAB+M silages had an equal quality. Silages treated with LAB, LAB+M, and SD took longer to heat than untreated silage when exposed to air(P<0.05), and improvements were numerically substantial. Inoculating alfalfa silage with LAB dramatically improved the aerobic stability of alfalfa haylage. These results indicated that alfalfa haylage produced in farm-scale silos treated with LAB could obtain the best quality.Experiment Ⅲ: The study was carried out to determine the effects of different additives on the in vitro gas production and its parameters and rumen fermentation parameters of wilted alfalfa herbage ensiled with lactic acid bacteria(LAB), lactic acid bacteria in combination with molasses(LAB+M) and sodium dehydroacetate(SD) in farm-scale silos according to single factorial randomized design. The 4 different alfalfa silages were come from the experiment II. Gas production(GP) and its parameters were studied by using an automatic in vitro gas production technique with ruminally fistulated Chinese Holstein dairy cows(average 550±25kg) in mid-lactation. At the end of the in vitro procedures, 72 h, the rumen fluid was analyzed for p H and volatile fatty acids, dry matter degradabilities(DMD) were also determined. The results showed that all treated silages had a rapid rise of GP in 0 to 6 h and after 24 h flatten out. At 72 h incubation, the cumulative gas production, the maximum fractional gas production rate and the time at which half of the gas produced for LAB+M was significantly higher than CK and LAB(P<0.05). The CK, LAB and SD-treated silage had lower maximum fractional gas production rate and 72 h in vitro DMD compared with LAB+M(P<0.05). Additives significantly increased the ammonia-N concentrations in the rumen fluid(P<0.05). At 72 h incubation, the rumen fermentation parameters did not differ between control and LAB and SD(P>0.05). The addition of LAB+M resulted in increased concentration of total VFA, acetic acid, propionic acid and butytic acid but lower acetate to propionate ratio compared with CK, LAB and SD(P<0.05). In general, the addition of LAB+M to alfalfa silage significantly increased the characteristics of gas production and reduced acetate to propionate ratio(P<0.05) and had a shift for the fermentation pattern. Our results indicate that adding LAB+M to alfalfa silage showed beneficial changes on improving nutritive value of silages compared with other treatments.Experiment Ⅳ: The study was carried out to determine the effect of different additives on the in situ rumen degradation of dry matter(DM), crude protein(CP), neutral detergent fiber(NDF) and acid detergent fiber(ADF) and its rumen fermentation kinetic parameters of wilted alfalfa herbage ensiled with lactic acid bacteria(LAB), lactic acid bacteria in combination with molasses(LAB+M) and sodium dehydroacetate(SD) in farm-scale silos according to single factorial randomized design. The 4 different alfalfa silages were come from the experiment II. Three Chinese Holstein dairy cows(average 550±25kg) in mid-lactation equipped with ruminally fistulae were used in this experiment. The results showed that the effective dry matter degradability was significantly higher(P<0.05) in the LAB+M-treated silage than CK and LAB or SD treatments. The higher degradable components(d) of NDF and ADF were found in the SD-treated silage than CK and LAB or LAB+M treatments(P<0.05). Additives addition had no significantly effect on CP degradation kinetic parameters and effective crude protein degradability(P>0.05), and the same effect on effective neutral detergent fiber degradability and effective acid detergent fiber degradability(P>0.05). This study shows that ensiling alfalfa with LAB+M increases effective dry matter degradability compared to other treatments which implied a better dry matter digestibility in the LAB+M-treated silage.In conclusion, The proper wilting and scientific usage of silage additives could reduce silage DM losses and improve fermentation characteristics as well as nutritive quality to a great extent. The using of additives in farm-scale silos also had significant effect of fermentation quality and nutrition value. It was suggested that inoculating alfalfa silage with LAB dramatically improved the aerobic stability of alfalfa haylage and treating with LAB+M could obtain the best nutritive quality. |
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