体外产气法评定不同留茬高度对全株玉米青贮体外发酵指标的影响

Effect of different stubble heights on in vitro fermentation indexes of whole maize silage by in vitro gas production method

试验旨在通过体外产气法评定不同留茬高度对全株玉米青贮发酵指标的影响,筛选出适宜留茬高度。试验以青贮用玉米品种吉祥1号为青贮材料,乳熟后期分为20、30和40 cm^(3)个留茬高度收割,桶内压实制作青贮。体外试验采用单因素试验设计,共3个处理,每个处理3个重复。结果显示,留茬40 cm组的全株玉米青贮粗蛋白质含量显著高于留茬20 cm组(P<0.05),留茬20 cm组的中性洗涤纤维和酸性洗涤纤维含量显著高于其他组(P<0.05);体外发酵指标中,留茬40 cm组72 h产气量比留茬20 cm组显著提高9.05 mL/g(P<0.05);体外发酵72 h后发酵液中,各组p H值、氨态氮浓度差异不显著(P>0.05),留茬20 cm组微生物蛋白含量显著低于其他组(P<0.05)。随留茬高度增加,留茬40 cm组总酸含量显著高于其他组(P<0.05),乙酸摩尔比例显著下降(P<0.05),留茬40 cm组丙酸摩尔比例显著高于其他组(P<0.05),且留茬40 cm组乙酸/丙酸显著低于留茬20 cm组和30 cm组(P<0.05);留茬40 cm组干物质消失率、中性洗涤纤维消失率和酸性洗涤纤维消失率显著高于其他组(P<0.05)。研究表明,参考营养成分和体外发酵指标,吉祥1号玉米制作的全株玉米青贮的适宜留茬高度为40 cm。

The experiment was to evaluate the effect of different stubble heights on fermentation patterns of whole corn silage by in vitro gas production method, to screen out the suitable stubble height. The test material was silage corn variety Jixiang No.1, which was harvested at three stubble heights of 20, 30 and 40 cm at later milky stage, compacted in a barrel to make silage. In vitro experiment was designed by single factor experiment with three treatments and three replicates in each treatment. The results showed that the crude protein content of whole corn silage in stubble group of 40 cm was significantly higher than that in stubble group of 20 cm(P<0.05), the content of neutral detergent fiber and acid detergent fiber in stubble group of 20 cm was significantly greater than that in other groups(P<0.05). For in vitro fermentation indicators, gas production in 72 h was 9.05 mL/g greater in stubble 40 cm group significantly higher than in stubble20 cm group(P<0.05). After 72 h in vitro fermentation, there was no significant difference in pH value and ammonia nitrogen concentration(P>0.05), the content of microbial protein in stubble group 20 cm was significantly lower than that in other groups(P<0.05). With the increase of stubble height, the total acid content in 40 cm stubble group was significantly higher than that in other groups(P<0.05),and the molar ratio of acetic acid was significantly decreased(P<0.05). The molar ratio of propionate in 40 cm stubble group was significantly greater than that in other groups(P<0.05), but the acetic acid/propionate in 40 cm stubble group was significantly lower than that in 20 cm and 30 cm stubble groups(P<0.05). Dry matter disappearance rate, neutral detergent fiber rate and acid detergent fiber rate in stubble group 40 cm were significantly greater than that in other groups(P<0.05). The experiment indicates that considering the nutrient composition and fermentation patterns in vitro, the suitable stubble height of the whole maize silage made by silage corn variety Jixiang 1 is 40 cm.