Muck R E, Filya I, Contreras-Govea F E
USDA, Agricultural Research Service, US Dairy Forage Research Center, Madison, WI 53706, USA.
J Dairy Sci. 2007 Nov;90(11):5115-25. doi: 10.3168/jds.2006-878.
Alfalfa silages from 2 similar trials were analyzed for in vitro ruminal gas production. In both trials, there were 15 treatments: alfalfa treated at ensiling with 1 of 14 lactic acid bacterial inoculants or untreated alfalfa. First-cut (477 g of dry matter/kg) and second-cut (393 g of dry matter/kg) alfalfa were ensiled in glass jars for a minimum of 35 d at room temperature (approximately 22 degrees C). At opening, a portion of each silage was wet-ground with a mixer. Each silage was then assessed for in vitro ruminal gas production in 3 replicate runs with the wet-ground silage, 1 on the fresh silage and 2 on frozen and thawed silage. In vitro gas production was measured in 160-mL sealed serum vials incubated at 39 degrees C. One gram of silage was incubated with 17.1 mL of nutrient solution, 0.9 mL of reducing solution, and 12 mL of ruminal inoculum (1:2 vol/vol mixture of rumen fluid and buffer). Gas production was measured manually by using a pressure gauge at 3, 6, 9, 24, 48, and 96 h. At 96 h, the rumen fluid was analyzed for pH and volatile fatty acids. In the 2 trials, the untreated control silage produced either numerically the highest or one of the highest levels of gas production per unit of dry matter incubated. In first-cut silage, 9 of the inoculant treatments at 9 h and 4 treatments at 96 h had reduced gas production compared with the control. In second-cut silage, 10 inoculant treatments at both 9 and 96 h had reduced gas production compared with the control. Furthermore, in first-cut silage, the fraction of total gas production at 3, 6, and 9 h was numerically the highest for the control, and only 4 treatments were not significantly lower than the control at 9 h. In second-cut silage, 2 of 14 inoculated treatments produced faster fractional rates of gas production than the control, but most inoculated treatments had numerically slower fractional rates (4 significant) in the first 9 h. The in vitro fermented wet-ground control silages had one of the highest acetate:propionate ratios in both trials, significantly higher than 12 and 8 of the inoculated treatments in first- and second-cut silage, respectively. The response in acetate:propionate ratio in both cuts was similar, even though the control silage was highest in lactic acid in one trial and lowest in the other. Overall, inoculation of crops at ensiling appears to affect in vitro ruminal fermentation of wet-ground silages, even in the absence of large effects during silage fermentation.
对来自2个相似试验的苜蓿青贮饲料进行了体外瘤胃产气分析。在这两个试验中，均有15种处理：用14种乳酸菌接种剂中的1种在青贮时处理苜蓿或未处理的苜蓿。头茬（477克干物质/千克）和二茬（393克干物质/千克）苜蓿在玻璃罐中于室温（约22摄氏度）下青贮至少35天。开封时，用搅拌机将每份青贮饲料的一部分湿磨。然后，对每种青贮饲料进行3次重复试验，测定其体外瘤胃产气情况，一次用湿磨青贮饲料，一次用新鲜青贮饲料，一次用冻融后的青贮饲料。体外产气在160毫升密封血清瓶中于39摄氏度下培养测定。1克青贮饲料与17.1毫升营养液、0.9毫升还原液和12毫升瘤胃接种物（瘤胃液与缓冲液的1:2体积/体积混合物）一起培养。在3、6、9、24、48和96小时时用压力计手动测量产气情况。在96小时时，分析瘤胃液的pH值和挥发性脂肪酸。在这两个试验中，未处理的对照青贮饲料按每单位培养干物质计算产生的气体量在数值上要么最高，要么是最高水平之一。在头茬青贮饲料中，9种接种剂处理在9小时时和4种处理在96小时时的产气与对照相比有所降低。在二茬青贮饲料中，10种接种剂处理在9小时和96小时时的产气与对照相比均有所降低。此外，在头茬青贮饲料中，3、6和9小时时总产气量的比例在数值上对照最高，在9小时时只有4种处理不比对照显著低。在二茬青贮饲料中，14种接种处理中有2种产生的产气分数速率比对照快，但在最初的9小时内，大多数接种处理在数值上产气分数速率较慢（4种显著）。在这两个试验中，体外发酵的湿磨对照青贮饲料的乙酸:丙酸比例均处于最高水平之一，分别显著高于头茬和二茬青贮饲料中12种和8种接种处理。尽管对照青贮饲料在一个试验中乳酸含量最高，在另一个试验中最低，但两茬中乙酸:丙酸比例的反应相似。总体而言，青贮时对接种作物似乎会影响湿磨青贮饲料的体外瘤胃发酵，即使在青贮发酵期间没有显著影响。
