Voluntary intake of silages in dairy cows depending on chemical composition and in vitro gas production characteristics

A study was conducted to investigate the possibilities to develop models for predicting the relative silage dry matter intake (SDMI) in dairy cows utilising information on chemical composition and in vitro gas production (GP) kinetics of silages. In five experiments, each with an average of 38 lactating dairy cows, SDMI was recorded for 15 grass silages made from primary growth and regrowth swards of timothy (Phleum pratense L.). The silages were characterised by chemical analysis and by utilising an automated in vitro GP recording technique with end point measurements of substrate residues. The silage samples were analysed both as dried and wet samples to evaluate the effects of sample preparation techniques on GP kinetics and their relations to SDMI. Relationships between feed variables and SDMI were investigated utilising simple linear and multiple regression. The wet silage samples had higher cumulative GP and different GP curves compared to the dried samples. The linear relationships between, GP variables, harvest number (first or second cut) of the grass, chemical characteristics of the silages and the relative SDMI show that the GP technique is a powerful tool to detect silage quality. By using the parameters from the dried samples the multiple regression analysis resulted in a relationship, relative SDMI (kg per 100 kg live weight (LW)) per day = 0.071 + 0.0029 × NDFD − 0.266 × C (R² = 0.82, S.D. = 0.06). NDFD is the degradability of the neutral detergent fibre (NDF) (g/kg NDF) and C is the variable that regulates the switching characteristics of the GP profiles. By using the wet silage samples the multiple relationship did not include any GP variable; relative SDMI (kg per 100 kg LW per day) = 1.86 − 0.008 × acetic acid (g/kg DM) + 0.024 × ethanol (g/kg DM) (R² = 0.62, S.D. = 0.08). The results from the regression analysis and the experience of the laborious sample preparation technique for wet samples, give the conclusion that dried silage samples are recommended for determining feed characteristics using the GP technique in intake studies.     

甲醛处理豆粕对蛋白质瘤胃降解及活体外瘤胃发酵的影响

通过尼龙袋试验和产气量试验研究甲醛处理大豆粕对瘤胃蛋白质降解率、产气量和活体外瘤胃发酵参数的影响。3个处理分别为对照组、处理Ⅰ和处理Ⅱ,其中处理Ⅰ、处理Ⅱ的甲醛添加量分别占大豆粕粗蛋白质(CP)0.6%和1.2%。研究结果表明:与对照组相比,处理Ⅰ和处理Ⅱ的干物质及蛋白质的降解率及降解速度显著下降(P<0.001),快速降解组分的比例和有效降解率显著下降,慢速降解组分比例显著提高(P<0.001),但两处理组之间干物质降解速度和蛋白质慢速降解组分比例均无显著差异(P>0.05)。与对照组相比,处理Ⅰ与处理Ⅱ的72h产气量和理论最大产气量均显著升高(P<0.001),而产气速度显著降低(P<0.005);甲醛处理对活体外瘤胃72h发酵的pH值、NH3-N浓度没有显著影响(P>0.05),但发酵液中丙酸摩尔比例显著上升(P<0.05),从而导致乙酸/丙酸降低。两个处理组活体外24h发酵液中甲醛浓度分别为0.994μg/mL和0.370μg/mL;而72h发酵液中甲醛浓度分别为0.410μg/mL和0.141μg/mL。本试验结论:甲醛处理能有效降低蛋白质在瘤胃内的降解率,并改善活体外发酵参数,其中甲醛添加量以占0.6%CP的处理更为有效。     

中链脂肪酸对体外发酵甲烷产量的影响

利用人工瘤胃体外产气法研究不同精粗比(0:1和1:1)日粮类型时中链脂肪酸对甲烷产量的影响。结果显示,体外培养24h,添加脂肪酸对甲烷产量的抑制作用不受日粮类型的影响(P>0.05);与不添加酸的对照相比,添加50mg未酯化月桂酸(C12:0)及月桂酸和肉豆蔻酸(C14:0)以3:2的比例组成的混合物(50mg)可分别抑制甲烷产量的22.2%(P<0.01)和11.8%(P<0.05);添加50 mg未酯化C14:0使甲烷产量降低3.4%(P>0.05);不同日粮类型上饲料产气量、瘤胃液pH值和氨氮浓度差异显著(P<0.01)。     

干旱胁迫对5个种源沙柳(Salix psammophila)气体交换及水分利用效率的影响

在盆栽条件下,对5个种源沙柳进行了水分胁迫处理,在不同干旱阶段对苗木叶水势、土壤含水率、蒸腾速率、光合速率等气体交换特性及水分利用效率进行了研究.结果表明:沙柳属于亚低水势忍耐脱水耐旱树种,叶水势随土壤含水量的下降而下降,变化趋势可用双曲线方程y=a b/x(0.389 0＜a＜0.520 3,8.906 6＜b＜11.466 9)拟合,其中民勤种源沙柳的双曲线方程中b值最低,为8.91,表现出较强的耐旱特性.在正常水分供应条件下,榆林种源沙柳的光合速率为23.89 μmol/(m2·s),水分利用效率为3.44 μmol/mmol,表现出很强的光合生产能力.随着干旱胁迫的加剧,各种源沙柳苗木的水分利用效率均有不同程度增加,民勤种源沙柳的增加值最大,为0.75 μmol/mmol,表现出了较强的抵抗干旱的能力,而榆林种源沙柳对水分亏缺则非常敏感,光合速率、蒸腾速率都急剧下降.这充分表明在水分供应充足的条件下,榆林种源沙柳具有最大的光合生产潜力;而当遇到干旱胁迫时,民勤种源沙柳则表现出极强的维持体内水分平衡的能力,是5个种源中最耐旱的种源.     

补充青贮玉米对复合稻草块体外发酵特性的影响

应用体外发酵产气技术,研究了青贮玉米以不同比例(0%～100%)替代复合稻草块中稻草对其体外发酵特性的影响。结果表明:随着青贮玉米比例的升高,复合稻草块的24h产气量、产气速度常数、有机物消化率、代谢能呈逐渐上升的趋势(P<0.05)。替代比例低于40%时24h产气量组合效应不显著(P>0.05),替代比例高于40%后出现逐渐增大的正组合效应,当替代比例为50%时,正组合效应值(9.68)显著增加(P<0.05),以后变动幅度不大。综上可见,用青贮玉米替代复合稻草块中40%以上的稻草较为适宜,当替代比例为50%时,就可获得较好的消化率。     

逆固相基质分散净化和气质联机检测土壤中的六氯苯残留

建立了逆固相基质分散净化和气质联机法(GC-MS)快速、简便测定土壤中六氯苯(HCB)残留量的方法。以丙酮-正己烷(1∶ 1,体积比)为提取剂,采用超声波萃取,经固相基质PSA(primary secondary amine)吸附净化后采用GC-MS选择离子模式检测。结果表明,六氯苯在0.05~5 mg/L浓度范围内呈现出较好的线性关系,相关系数R2=0.999 5; 方法检测限为0.3 μg/kg,定量限为0.9 μg/kg,在0.89、1.78、8.90 mg/kg 3个添加水平上的平均回收率分别为106.6％、108.2％和108.1％。用该方法测定了天津某生产厂厂区地下1~10 m深的土壤样本,发现六氯苯的残留量在2.3~25 912 mg/kg 之间,表现出显著的空间变异趋势。该方法快速、简便、经济、高效、实用并且安全,适合大批量样本中六氯苯的快速检测。     

仲丁威三种测定方法的比较

本文采用反相高效液相色谱法和改进的气相色谱法对仲丁威含量进行了测定,并与ＣＩＰＡＣ采用的正相高效液相色谱法测定了进行了比较。结果表明,反相液相色谱法与正相液相色谱法等效,气相色谱法经改进后降低了仲丁威的热分解,三种方法对仲丁威原药及乳油含量的测定结果的相对误差在允许的范围之内。     

Collection,Analysis, and Utilization of Biogas from Anaerobic Treatment of Crab Processing Waters

Abstract

Two laboratory-scale, upflow anaerobic reactors were constructed to treat blue crab (Callinectes sapidus) cooking wastewater for determination of the volume and composition of the resulting bio-gas. Both systems (A and B) consisted of two 4-liter (L) upflow anaerobic reactors and one 8-L aerobic reactor in series. The first anaerobic reactor of System A contained 240,12.7 mm foam cubes, while the first anaerobic reactor of System B contained 180 foam pieces (25.4 ×25.4 ×12.7 mm). Biogas production rates for System A ranged from 6.6 L gas/L feed to 10.0 L gas/L feed. Mean values for System B ranged from 7.1 L gas/L feed to 11.9 L gas/L feed. Methane and carbon dioxide comprised 68% and 28%, respectively, of the gas from both systems. Hydrogen sulfide averaged 1.5% and 1.4% for systems A and B, respectively. A pilot-scale biogas collection and utilization system was also constructed and successfully demonstrated. Details of the pilot-scale system design are provided in the paper to help processors better understand how the technology might be applied.     

不同工艺对牛粪堆沤肥过程气体排放的影响

堆沤肥是中国畜禽粪便处理利用的最主要方式。为探究不同堆沤肥方式对温室气体和氨气排放规律和温室效应，在北京市密云区开展了为期71d的堆沤肥试验，以牛粪和玉米秸秆为原料，分析了静态堆沤 (T1)、堆沤+翻抛 (T2)、堆沤+覆膜 (T3)、翻抛+覆膜 (T4)等4种方式对堆沤肥过程中腐熟度、温室气体和氨气等指标的影响。结果表明，4个处理的种子发芽指数分别达到131.33%、134.49%、108.76%和136.24%，均满足堆肥产品的腐熟度要求（≥70%）。翻抛有利于CO₂、N₂O和NH₃的排放，而覆膜抑制了N₂O的生成，T2处理的增温潜势最高，T3处理的增温潜势最低，较对照组T1处理减排20.14%。因此，T3处理在能够保证堆肥产品的腐熟度要求的前提下，还可有效减少增温潜势。该研究可为中小养殖场户堆沤肥的工艺优化实践提供技术指导。     

提高天然气流量计量的准确度

叙述了天然气计算技术的现状及发展趋势，分析了孔板流量计在天然气工业应用中存在的问题，指出了提高天然气流量计量准确度的措施，提出了解决孔板开孔直角入口边缘尖锐度钝化和测量范围窄等问题的新思路。