日粮不同NDF/NFC水平对周岁后荷斯坦奶牛生产性能、营养物质消化率、瘤胃发酵特征和甲烷排放的影响

本试验研究了日粮中不同中性洗涤纤维/非纤维性碳水化合物（NDF/NFC）水平对周岁后荷斯坦奶牛生产性能、营养物质消化率、瘤胃发酵特征及甲烷产量的影响，并在此基础上建立了甲烷排放预测模型，旨在获得我国生产模型下的甲烷排放规律和甲烷转化因子，为提高奶牛能量利用效率、建立国家或区域性温室气体排放清单和探索减排策略提供科学依据和支撑。将45头体况良好，平均为15月龄的荷斯坦后备奶牛随机分为3组，每组15头牛：低日粮NDF/NFC组（NDF/NFC=0.60）、中日粮NDF/NFC组（NDF/NFC=0.75）和高日粮NDF/NFC组（NDF/NFC=0.90），试验期为70 d，包括14 d的预饲期和56 d的正试期。结果表明：1）提高日粮NDF/NFC水平显著降低了奶牛的干物质采食量、有机物采食量、平均日增重、干物质和粗蛋白的表观消化率（P<0.05）；2）提高日粮NDF/NFC水平显著增加了瘤胃内总挥发性脂肪酸产量、乙酸的相对含量和乙酸/丙酸比例（P<0.05），显著降低了丙酸的相对含量（P<0.05）；3）随着日粮NDF/NFC水平的提高，瘤胃甲烷和甲烷能产量、甲烷/代谢体重、甲烷/干物质采食量、甲烷/有机物采食量、甲烷/中性洗涤纤维采食量显著提高（P<0.05）。甲烷转化因子也随着日粮NDF/NFC水平的增加而显著提高（P<0.05）；4）基于体重、采食量、营养物质含量和NDF/NFC分别建立了甲烷预测模型，其中基于干物质采食量和中性洗涤纤维采食量建立的预测模型的决定系数最高（R²=0.77）。因此，提高日粮中NDF/NFC水平可显著降低周岁后荷斯坦奶牛的生产性能、营养物质消化率和瘤胃内丙酸的相对含量，可显著提高瘤胃甲烷产量和甲烷转化因子。     

Energy and protein requirements for maintenance of Hu sheep during pregnancy

This study aimed to determine the effect of stage and level of feed intake on energy metabolism,carbon-nitrogen(C-N)balance,and methane emission to determine energy and protein requirements for maintenance of maternal body including pregnancy tissues during pregnancy using the method of C-N balance.Twenty-one ewes carrying twin fetuses were randomly divided into three groups of seven ewes each in the digestion and respirometry trial at d 40,100,and 130 of gestation,respectively.Three groups were fed a mixed diet either for ad libitum intake,70 or 50%of the ad libitum intake during pregnancy.The results showed that the apparent digestibility of C and N were increased as feeding levels decreased at each stage of gestation.The daily net energy requirements for maintenance(NE_m)were 295.80,310.09,and 323.59 k J kg~(–1)BW~(0.75)(metabolic body weight)with a partial efficiency of metabolisable energy utilization for maintenance of 0.664,0.644,and 0.620 at d 40,100,and 130 of gestation,respectively.The daily net protein requirements for maintenance were 1.99,2.35,and 2.99 g kg~(–1 )BW~(0.75) at d 40,100,and 130 of gestation,respectively.These results for the nutritional requirements of the net energy and protein may help to formulate more balanced diets for Hu sheep during pregnancy.     

Effects of dietary supplementing tannic acid in the ration of beef cattle on rumen fermentation,methane emission,microbial flora and nutrient digestibility

Four adult Simmental male cattle (376 ± 9.0 kg initial BW), fitted with permanent rumen cannulas, were used in a 4 × 4 Latin square design to investigate the effects of dietary supplementing tannic acid (TA) on rumen fermentation, methane (CH₄) production, rumen microbes, nutrient digestibility and plasma biochemical parameters. Four levels of TA, that is 0, 6.5, 13.0 or 26.0 g/kg dry matter (DM), were added to the basal ration (composed of corn silage and concentrate mixture) as experimental treatments respectively. Each experimental period consisted of a 12‐day adaptation phase followed by a 3‐day sampling phase. The results showed that supplementing TA at 26.0 g/kg DM decreased the relative abundance of protozoa, methanogens and Ruminococcus albus to the total ruminal bacterial 16S rDNA in beef cattle (p < 0.05). The results also showed that supplementing TA at 6.5, 13.0 or 26.0 g/kg DM decreased (p < 0.01) the CH₄ production (l/kg DM intake) by 11.1%, 14.7% and 33.6% respectively. Supplementing TA at 13.0 or 26.0 g/kg DM decreased the ratio of acetate to propionate and ammonia nitrogen (NH₃–N) (p < 0.05) and tended to decrease the total volatile fatty acid (VFA) concentration of rumen fluid (p = 0.07). Supplementing TA at 26.0 g/kg DM decreased DM and organic matter (OM) digestibility (p < 0.05), supplementing TA at 6.5, 13.0 or 26.0 g/kg DM decreased (p < 0.01) crude protein (CP) digestibility by 5.0%, 8.6% and 15.7%, respectively, and supplementing TA at 6.5, 13.0 or 26.0 g/kg DM increased (p < 0.05) the plasma total antioxidant capability. It was concluded that supplementing TA in the ration of beef cattle decreased the CH₄ production and digestibility of CP of beef cattle. Supplementing TA could be an effective option to mitigate CH₄ emission form cattle, further research is necessary to study the effects of TA on the performance of cattle.     

不同有机肥对稻田温室气体排放及产量的影响

为研究有机肥施入稻田对温室气体排放的影响,设置猪粪、鸡粪和稻草分别与化肥混施处理,利用静态箱法-气相色谱仪监测稻田甲烷(CH_4)和氧化亚氮(N_2O)排放通量并进行分析。研究结果表明,化肥处理(CF)CH_4季节排放为202.1、279.9和332.5 kg/hm~2,与猪粪(PM)无显性差异,明显低于鸡粪(CM)和稻草(RS)处理;CF处理N_2O排放总量最高,与有机肥处理无显著性差异;CH_4季节排放通量与土壤Eh值呈极显著负相关关系,与土壤温度呈极显著正相关关系;肥料中不同活性有机碳质量分数为18.4~114.5 g/kg,肥料中被167 mmol/L高锰酸钾氧化的有机碳(ROC167)与稻田CH_4排放总量呈显著正相关关系(相关系数为0.872,P0.05);施有机肥第三年水稻平均产量比CF处理增加14.3%(P0.05);不同有机肥中,以PM处理的增温潜势和温室气体排放强度最小,与不施肥和CF处理无显著性差异,猪粪的ROC167含量低,能较好的协调环境与产量之间关系,是值得推荐的有机肥种类。     

Converting conventional agriculture to poplar bioenergy crops: soil greenhouse gas flux

Conversion of agricultural fields to bioenergy crops can affect greenhouse gases (GHG) such as carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Soil GHG emissions were measured seasonally in poplar bioenergy and agricultural fields at three Northwestern US locations. A forest stand was also used at one location for comparison. A portable gas analyzer was used to measure CO₂ efflux and CH₄ and N₂O fluxes were first measured with chambers and later with gradients. Agricultural soil had 17% larger CO₂ efflux rates than poplar soil. Chamber fluxes showed no differences in CH₄ uptake but did show higher N₂O fluxes in poplar than agricultural soil. Gradient CH₄ uptake rates were highest in agricultural soil in the summer but showed no N₂O flux differences. Forest soils had smaller quarterly CO₂ efflux rates than agricultural soils and greater CH₄ uptake rates than poplar soils. The largest GHG contributor to soil GHG flux was CO₂, with those being ～1000 times larger than CH₄ flux rates and ～500 times larger than N₂O flux rates based on CO₂ equivalences. Converting conventional agricultural cropland to poplar bioenergy production does not have adverse effects on soil greenhouse gas flux and these results could be useful for modeling or life cycle analysis of land use conversion.     

水合氧化铁提前施用对持续淹水条件下水稻甲烷的减排效应

水合氧化铁是一种弱晶质三价铁氧化物,可用来减少稻田甲烷（CH4）的排放。采用水稻盆栽试验,研究水合氧化铁的提前施用对持续淹水条件下水稻CH4排放的影响。结果表明:水合氧化铁在水稻移栽前47 d施用,加Fe处理的全生育期CH4总排放通量比对照减少17.52%,其CH4减排效应仅出现于水稻生长后期。在移栽后第70天,加Fe处理的根孔隙度、根表铁膜含量和单株根表铁膜数量均显著高于对照,而稻根产CH4速率则显著低于对照。因此,提前施用水合氧化铁能够通过促进植株介导的根表铁膜的形成抑制稻根的产CH4潜力,进而实现持续淹水条件下水稻CH4的减排。     

海带渣与养殖固体废弃物混合发酵产沼气试验

废弃物的高效和资源化利用是现代渔业发展面临的重要课题。该文以海带渣和养殖固废为原料开展了两相发酵产沼气效果试验研究,探讨了中温条件下(35±1℃)料液TS浓度和接种率对混合水解酸化特性以及厌氧发酵产沼气效果的影响。结果表明,海带渣与养殖固废混合水解酸化过程启动很快,第2天乙酸浓度即达到峰值,5 d后丙酸和丁酸浓度增幅较快,水解酸化过程中甲酸产量相对较低。不同TS浓度(6%、8%和10%)和不同接种率(10%、20%和30%)的料液水解3 d,乙酸的酸化度分别为42.6%、50.0%、49.8%和50.7%、44.3%、40.3%;主要有机酸(乙酸+丁酸+甲酸)的酸化度分别达到61.7%、68.7%、62.2%和69.4%、57.5%、58.0%。料液TS浓度为8%~10%、接种率为10%~20%和p H值为6.0~7.0时,海带渣与养殖固废在中温条件下混合水解2~3 d,即可获得后期发酵产沼气所需的酸化料液。此外,发酵产沼气结果表明,每天按与产沼气接种污泥质量比为1:7~1:9的比例添加酸化料液,在p H值为7.0~8.0和35±1℃的条件下厌氧发酵产沼气,产气系统启动很快,而且8~13 d即进入稳定产气阶段,产气率保持在489.4~581.5 m L/g VS,所产沼气中的甲烷体积分数达到82.7%~84.9%,而且料液不会出现酸化现象。海带渣与养殖固废混合水解酸化、批量填料发酵产沼气工艺明显提高了产气效率和系统稳定性。     

Effects of different molecular weights of chitosan on methane production and bacterial community structure in vitro

As a new feed additive, chitosan has been shown in recent years to have a certain role in reducing methane emissions from the gastrointestinal tracts of ruminants. However, the effects of chitosan with different molecular weights on rumen fermentation, methane production and bacterial community structure are not yet clear. A basal diet without chitosan served as the control(CTL), and the treatment diets were supplemented with chitosan with different molecular weights: 1 000(1K), 3 000(3K), 5 000(5K), 50 000(5W) and 200 000(20W) dry matter(DM). Six fermentation units per treatment were established. Gas chromatography was used to measure the concentrations of methane, H_2 and volatile fatty acids(VFAs). The bacterial 16S rRNA genes were sequenced with an Illumina MiSeq platform and analysed to reveal the relative abundances of bacterial community taxa. The results showed that the propionate proportion was significantly increased by the addition of chitosan with different molecular weights(P0.05), while methane production and the acetate proportion were significantly decreased(P0.05). The relative abundances of Rikenellaceae_RC9_gut_group and Prevotellaceae_UCG_003 were significantly increased in the 3K chitosan group compared with the CTL group, whereas the relative abundance of Ruminococcaceae_NK4A214_group was significantly decreased(P0.05). Correlation analyses of the relative abundances of the bacterial genera showed that Prevotella was positively related to propionate production(P0.05). In conclusion, 3K chitosan could reduce methane production by replacing fibrolytic bacteria(Firmicutes and Fibrobacteres) with amylolytic bacteria(Bacteroidetes and Proteobacteria) in the bacterial community structure.     

体外法研究硝酸钠调控水牛瘤胃甲烷生成对脂肪酸生物氢化途径的影响

本试验旨在研究硝酸钠调控水牛瘤胃甲烷生成对脂肪酸生物氢化途径的影响。选取3头体重约为（650±50）kg、安装永久性瘤胃瘘管的水牛作为瘤胃液供体动物，通过体外批次培养，设计发酵底物的精粗比为40：60，试验设4个组，每组5个重复，每组各添加0.25 mg/mL的α-亚麻酸，硝酸钠添加水平分别为0（对照）、1、2、3 mg/mL。分别培养3、6、9、12、24 h时测定产气量和甲烷产量，在培养24 h结束后测定体外发酵参数和脂肪酸含量。结果表明：①添加硝酸钠显著降低了瘤胃培养液24 h的总产气量、甲烷（CH₄）含量和甲烷/总产气量的比例（P<0.05），添加1、2和3 mg/mL硝酸钠后瘤胃液甲烷含量分别降低了89.62%、91.20%、91.75%。②添加硝酸钠组瘤胃培养液的pH和氨态氮（NH₃-N）含量显著高于对照组（P<0.05），添加1 mg/mL硝酸钠组微生物蛋白（MCP）含量也显著高于对照组（P<0.05），其他组别差异不显著（P>0.05）；添加硝酸钠组瘤胃液乙酸浓度差异不显著（P>0.05），但丙酸、丁酸、异丁酸、戊酸和异戊酸浓度显著低于对照组（P<0.05），乙酸/丙酸显著高于对照组（P<0.05），添加3 mg/mL硝酸钠组瘤胃液总挥发性脂肪酸（TVFA）含量显著低于对照组（P<0.05）。③添加1 mg/mL硝酸钠组瘤胃液C18：2 cis-9，trans-11、C18：2 trans-10，cis-12、C20：1、不饱和脂肪酸（UFA）含量及UFA/SFA显著高于其他组（P<0.05）；添加硝酸钠组瘤胃液C18：2n6c、C18：1n9t、C20：5n3（EPA）和C22：6n3（DHA）的含量均高于对照组，且1 mg/mL硝酸钠组含量最高，但差异不显著（P>0.05）；添加1 mg/mL硝酸钠组瘤胃液C18：3n3、C18：2n6c和C18：1n9c含量均高于对照组，差异不显著（P>0.05）。由此可见，体外添加硝酸钠显著降低了瘤胃液总产气量和甲烷含量，pH和NH₃-N含量显著升高，TVFA含量降低，通过显著减少丙酸含量而升高乙酸/丙酸；添加1 mg/mL硝酸钠可显著提高瘤胃液共轭亚油酸（CLA）和UFA含量，且在抑制甲烷产生的同时能够降低不饱和脂肪酸的生物氢化程度。     

Process performance of anaerobic co-digestion of waste activated sludge and aquaculture sludge

The mesophilic anaerobic co-digestion (AcD) performances of waste activated sludge (WAS) and aquaculture sludge (AS) were studied. Mixtures of different compositions (0, 30, 50, 70 and 100 % of AS on the volume basis) were used as AcD substrates and tested via biochemical methane potential assay. The results showed that CH₄ production increased with AS/WAS ratio increment, and AS alone used as the substrate showed the maximum CH₄ yield, which was 8% higher than that achieved using WAS alone as the substrate. The CH₄ yield values were well fitted with the modified Gompertz model. The maximum methane potential (P₀) and maximum methane production rate (R₀) increased from 66.8 mL CH₄/g VS_fed to 70.9 mL CH₄/g VS_fed and from 4.40 mL CH₄/g VS_fed·d to 5.59 mL CH₄/g VS_fed·d, respectively, as the AS/WAS ratio increased from 0% to 100 %. In addition, lower levels of free ammonia and non-biodegradable organic matter contributed to the CH₄ production increasing with AS/WAS ratio increased.