体外法评价青贮玉米与青贮菠萝渣的组合效应

【目的】通过体外产气法探讨青贮玉米与青贮菠萝渣的最佳组合比例，为开发南方地区青贮玉米和菠萝渣资源提供参考。【方法】将青贮玉米与青贮菠萝渣以100:0、75:25、50:50、25:75、0:100 （干物质）分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ组，进行体外发酵（3、12、24和48 h），每个时间点设3个重复，2个空白对照。发酵结束时测定各发酵时间点的pH、产气量、挥发性脂肪酸及发酵滤渣中的干物质降解率（DMD）、粗蛋白降解率（CPD）、中性洗涤纤维降解率（NDFD），并计算挥发性脂肪酸、DMD、CPD、NDFD的单项组合效应指数和多项组合效应指数。【结果】在整个发酵期内，随发酵时间推移，各试验组的pH显著降低（P<0.05，下同）；产气量、DMD、CPD、NDFD、总挥发性脂肪酸（TVFA）显著增加；乙酸和丙酸浓度先升高后降低。混合组在发酵初期，产气量偏低，TVFA、乙酸、丙酸和丁酸浓度随青贮菠萝渣比例提高呈先升高后降低趋势；发酵后期，TVFA、乙酸、丙酸和丁酸浓度随青贮菠萝渣比例提高呈显著升高。Ⅳ组的CPD与NDFD的单项组合效应指数为正值，而DMD的单项组合效应指数为负值（除3 h外），Ⅲ组和Ⅳ组的TVFA、乙酸、丙酸和丁酸（除48 h外）浓度的单项组合效应指数均为正值。发酵初期（3和12 h），Ⅲ组的多项组合效应指数最高，分别为3.83和11.85；发酵后期（24和48 h），Ⅳ组的多项组合效应指数最高，分别为20.01和21.71。【结论】青贮玉米与青贮菠萝渣比例为25: 75时多项组合效应指数最大，有助于瘤胃微生物生长代谢，提高营养物质的降解率。

Evaluation of associative effect of silage corn and silage pineapple residue by in vitro method

【Objective】To determine ideal ratio of silage corn(SC) and silage pineapple residue(SPR) through in vitro gas generation method, so as to provide guidance for silage corn and silage pineapple residue resource development in southern China.【Method】SC and SPR were mixed in ratios of 100:0, 75:25, 50:50, 25:75, 0:100 and divided into group Ⅰ, Ⅱ, Ⅲ, Ⅳ and Ⅴ. And sample in groups Ⅰ, Ⅱ, Ⅲ, Ⅳ, and Ⅴ were cultured in vitro(3, 12, 24, 48 h). Triplicates were used for each group and 2 blank controls were used for each time point. At the end of each time point, pH, gas production, volatile fatty acids and dry matter degradability(DMD), crude protein degradability(CPD), neutral detergent fiber degradability(NDFD), and calculated the single factor associative effect value of volatile fatty acids, DMD, CPD, NDFD, and multiply factors associative effects index were determined when fermentation ended.【Result】During fermentation, with the passage of time, each pH of each group decreased significantly(P<0.05, the same below);gas production, DMD, CPD, NDFD, total volatile fatty acids (TVFA) increased significantly; concentration of acetic acid(AA) and propionic acid(PA) increased first and then decreased. Early in the fermentation, gas production was low, and the concentrations of TVFA, AA, PA, and butyric acid(BA) increased first before decreasing as the proportion of pineapple residue silage increased. In final part of fermentation, concentrations of TVFA, AA, PA, and BA increased significantly. The single factor associative effect value of CPD and NDFD in group Ⅳ was positive, while the single factor associative effect value of DMD was negative(except for that of 3 h fermentation), and TVFA, AA, PA, and BA(except for that of 48 h fermentation) in group Ⅲ and group Ⅳ were positive. The multiply factor associative effects index of group Ⅲ was the highest at the early stage of fermentations(except for that of 3 h and 12 h fermentation), which 3.83 and 11.85, respectively. The multiply factor associative effects index of group Ⅳ was the highest at the later stage of fermentations(24 h and 48 h), which 20.01 and 21.71, respectively.【Conclusion】The multiple combination impact index is greatest when the ratio of silage corn to silage pineapple residue is 25:75, which promotes rumen microbe proliferation and metabolism and speeds up nutrient decomposition.