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1.
LANG Man 《干旱区科学》2021,13(5):487-499
The soil type is a key factor influencing N(nitrogen) cycling in soil; however, gross N transformations and N_2O emission sources are still poorly understood. In this study, a laboratory ~(15)N tracing experiment was carried out at 60% WHC(water holding capacity) and 25℃ to evaluate the gross N transformation rates and N_2O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province, China. The results showed that the gross rates of N mineralization, immobilization, and nitrification were 3.60, 1.90, and 5.63 mg N/(kg·d) in silt loam soil, respectively, which were 3.62, 4.26, and 3.13 times those in sandy loam soil, respectively. The ratios of the gross nitrification rate to the ammonium immobilization rate(n/ia) in sandy loam soil and silt loam soil were all higher than 1.00, whereas the n/ia in sandy loam soil(4.36) was significantly higher than that in silt loam soil(3.08). This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil, and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO_3~– leaching. Under aerobic conditions, both nitrification and denitrification made contributions to N_2O emissions. Nitrification was the dominant pathway leading to N_2O production in soils and was responsible for 82.0% of the total emitted N_2O in sandy loam soil, which was significantly higher than that in silt loam soil(71.7%). However, the average contribution of denitrification to total N_2O production in sandy loam soil was 17.9%, which was significantly lower than that in silt loam soil(28.3%). These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.  相似文献   
2.
目前,我国豆渣年产量高但利用率低,浪费严重。豆渣中含有丰富的膳食纤维,具有独特的保健功能。本文在传统酸奶的基础上,添加豆渣膳食纤维,研制膳食纤维保健酸奶。采用因素控制法,确定了复合酶法提取豆渣膳食纤维的工艺条件;利用正交试验设计优化了酸奶的制作工艺。结果表明,复合酶法提取豆渣膳食纤维的最佳工艺为木瓜蛋白酶添加量6%,α-淀粉酶添加量2%,酶解时间90 min,此时豆渣膳食纤维提取率达74.26%;豆渣膳食纤维酸奶的最优工艺条件为豆渣膳食纤维量1.8%,乳酸菌粉添加量3.5%,蔗糖添加量7%,稳定剂果胶添加量0.5%,发酵温度40℃,发酵时间3.5 h,在此条件下制得的酸奶色泽柔和均一,凝乳均匀细腻,具有纯正的乳酸发酵香味。  相似文献   
3.
本研究旨在探讨谷物膳食纤维(DF)对高胆固醇饮食小鼠的脂质代谢和肠道菌群的影响。选取C57BL/6J小鼠30只,并根据体重随机分为4组,分别饲喂基础饲粮(对照,CO组,n=8)、基础饲粮+5 g/kg DF(CO+DF组,n=8)、高脂高胆固醇饲粮(HF组,n=7)及高脂高胆固醇饲粮+5 g/kg DF(HF+DF组,n=7)。试验期8周,测定各组小鼠生长性能、血清和肝脏生化指标、粪便总胆固醇(TC)、短链脂肪酸(SCFA)、相关肝脏胆固醇和胆汁酸(BA)蛋白表达及肠道菌群。结果表明:1)CO+DF组的最终体重显著低于CO组(P<0.05),与HF组相比,CO组和HF+DF组的4周和最终体重均显著降低(P<0.05),肝脏和脂肪的重量显著减少(P<0.05)。且与HF组相比,DF+HF组摄食效率显著降低(P<0.05)。2)CO+DF组血清TC、甘油三酯(TG)含量及天冬氨酸转氨酶(AST)和丙氨酸转氨酶(ALT)活性以及肝脏TC和TG含量显著低于CO组(P<0.05),CO组和HF+DF组显著低于HF组(P<0.05),粪便TC含量仅在HF+DF组显著低于HF组(P<0.05)。3)DF对肝脏胆固醇调节元件结合蛋白-2(SREBP-2)、3-羟基-3-甲基戊二酰辅酶A还原酶(HMGR)、肝脏X受体α(LXRα)、微管相关蛋白1轻链3-Ⅰ(LC3-Ⅰ)和微管相关蛋白1轻链3-Ⅱ(LC3-Ⅱ)蛋白表达没有显著影响(P>0.05)。CO+DF组肝脏胆固醇7-羟化酶(Cyp7a1)的蛋白表达水平显着低于CO组(P<0.05),但HF组和HF+DF组之间没有显著差异(P>0.05)。4)HF+DF组的粪便总SCFA和丙酸盐含量显著高于HF组(P<0.05)。与相应的对照组相比,CO+DF组和HF+DF组的粪便丁酸盐含量显著增加(P<0.05)。5)在门水平上,DF组厚壁菌门(Firmicutes)相对丰度减少,HF+DF组的拟杆菌门(Bacteroidetes)相对丰度高于HF组。梭状芽孢杆菌属ⅪⅤa(ClostridiumⅪⅤ)相对丰度在CO+DF组和HF+DF组显著增加(P<0.05)。此外,与其他组相比,仅HF+DF组中阿克曼菌属(Akkermansia)相对丰度显著增加(P<0.05)。由此可见,每千克饲粮添加5 g DF可降低饲喂含脂45%饲粮小鼠的体重和肝脏脂肪含量,降低血清TC、TG含量及AST和ALT活性以及肝脏TC和TG含量,降低胆固醇合成相关蛋白Cyp7a1的表达水平,提高总SCFA含量及肠道有益菌群和优势菌群相对丰度。  相似文献   
4.
A 4‐week feeding trial was conducted using five groups of hybrid grouper (61.15 ± 0.15 g) to explore the potential effects of three methionine (Met) sources. Five isonitrogenous and isolipidic diets were formulated that included a fishmeal (FM) diet; nonsupplemented (NS) diet; or NS diets with the addition of the L‐methionine (L‐Met), DL‐methionine (DL‐Met), or coated Met (Co‐Met) to obtain the same Met level as the FM diet. Fish were randomly distributed into sea cages (30 fish per cage). Weight gain and specific growth rate in the DL‐Met group and FM group were significantly higher than those in all other groups (p < .05). In the proximal and distal intestines, of the 20 gene and time combinations (10 per gene), there were 14 combinations (70%) in which there were no significant differences in gene expression levels between the FM and DL‐Met groups (p > .05). The main reason for the same growth effect between the DL‐Met and FM groups may be attributed to the synchronized absorption at most time points after feeding, which had similar expression patterns of B0AT1 and ASCT2 of the proximal and distal intestines between two groups.  相似文献   
5.
本文在总结分析国内外最新研究成果的基础上,对非饲草来源纤维(NFFS)对奶牛的营养作用和生理影响及其机理进行了综述,主要从NFFS部分替代饲草对奶牛生产性能、瘤胃草垫层和瘤胃发酵的影响,以及NFFS部分替代精料对饲料效率、生产性能和亚急性瘤胃酸中毒(SARA)奶牛生理的影响等方面进行论述,旨在为NFFS饲料在奶牛饲粮中的科学合理利用提供理论参考和依据。  相似文献   
6.
为了解决农业设备位移的宽量程、高灵敏度非接触测量问题,提出一种基于Peanut-shape迈克尔逊干涉结构的非接触式光纤位移传感器。分析了光纤Peanut-shape迈克尔逊干涉原理,设计了将磁场与Peanut-shape结构形成的全纤式迈克尔逊干涉相结合的传感器结构,并通过磁场仿真,得到磁场强度曲线。建立了传感器应变标定系统和位移测试系统。试验结果表明:Peanut-shape迈克尔逊干涉的光纤传感器应变灵敏度达到1. 82 pm/με,是普通光纤的1. 5倍,线性度为0. 997;位移测试得到的光谱曲线与磁场仿真曲线结果一致,可以实现位移的测量,且线性拟合度达到0. 999。  相似文献   
7.
8.
The phytoavailability of soil phosphorus (P) depends on the different forms in which it occurs and how these forms change after the application of P fertiliser to the soil. Forms of P in the A, B and C horizons of eleven pedons that developed on mafic rocks were characterised by a fractionation method before and after fertilisation with single superphosphate, and a micropot experiment was conducted to assess the short-term use of P fertiliser by rye (Secale cereale L.). The main sources of P to the crop were (i) phosphate adsorbed on mineral surfaces and pedogenic Fe, Al or Ca phosphates in the A horizon and (ii) Ca-phosphates in B and C horizons. In the C horizons, poor in Fe/Al phases and clay, the precipitated Ca-P showed low solubility, resulting in a reduction in shoot biomass. The apparent P recovery by rye was similar in the A (36%) and B (29%) but decreased in the C (15%) horizons. The partial factor productivity (g g?1) decreased from the A (58) to B (11) and C (5) horizons. P phytoavailability decreased with increasing profile depth because the transformation of P fertiliser to poorly soluble Ca-P forms increased with depth.  相似文献   
9.
为研究开式纸浆泵叶轮流道内纤维颗粒对液相流场的影响,采用透明有机玻璃材料制造模型样机,以清水和0.1%质量浓度的头发纤维悬浮液为介质,通过PIV试验对叶轮流道内的流动进行可视化研究.试验结果表明:当输送清水介质时,在大流量工况下叶轮流道内流动稳定,未出现旋涡和低速区;在小流量工况下,当叶轮流道旋转到蜗壳隔舌附近位置时,在叶轮流道中段压力面附近开始产生低速区,且低速区随着叶轮流道靠近隔舌位置和流量减小逐渐增大,在远离隔舌位置的叶轮流道内未产生明显的低速区;受叶片扭曲的影响,在叶轮流道内垂直于泵轴的不同截面上的相对速度大小不同,且随着叶片扭曲程度减小,相对速度差减小;输送头发纤维悬浮液介质时,在纤维颗粒的影响下,叶轮流道内的液相流动相对速度降低,导致在小流量工况下叶轮流道中段压力面附近低速区面积增大;在大流量工况下,纤维颗粒存在使液相流动的相对速度大小分布更均匀.  相似文献   
10.
Rumen digesta was obtained from wild Hokkaido sika deer to compare bacterial flora between summer and winter. Bacterial flora was characterized with molecular‐based approaches and enrichment cultivation. Bacteroidetes was shown as a major phylum followed by Firmicutes, with similar proportions in both seasons. However, two phylogenetically unique groups in Bacteroidetes were found in each season: unknown group A in winter and unknown group B in summer. The ruminal abundance of unknown group A was the highest followed by Ruminococcus flavefaciens in winter. Moreover, the abundance of these two was higher in winter than in summer. In contrast, the abundance of unknown group B was higher in summer than in winter. In addition, this group showed the highest abundance in summer among the bacteria quantified. Unknown group A was successfully enriched by cultivating with oak bark and sterilized rumen fluid, particularly that from deer. Bacteria of this group were distributed in association with the solid rather than the liquid rumen fraction, and were detected as small cocci. Accordingly, unknown group A is assumed to be involved in degradation of fibrous materials. These results suggest that wild Hokkaido sika deer develop a rumen bacterial flora in response to changes in dietary conditions.  相似文献   
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