绵羊瘤胃微生物胞外蛋白酶性质的研究

本试验测定了pH、温度和EDTA对纯化的绵羊的瘤胃微生物胞外蛋白酶活性的影响,并用一已知氨基酸排列顺序的肽段(由15个氨基酸组成)作为底物,进一步测定了蛋白酶的酶切位点。结果表明,(1)纯化蛋白酶的最适pH在6.0～6.5之间,最适温度为40℃左右。(2)不同浓度的EDTA(浓度分别为1,10,25,50,75和100mM)对蛋白酶活性没有影响,因而该酶属于丝氨酸蛋白酶类。(3)纯化蛋白酶是一种内肽酶,其酶切位点在组氨酸—酪氨酸(?)、天冬氨酸—丙氨酸(?)、亮氨酸—赖氨酸(?)和(或)缬氨酸—赖氨酸(?)相连的肽键。(4)胰蛋白酶和纯化的蛋白酶虽同属丝氨酸蛋白酶类,但前者对底物具有高度的专一性,后者对底物的专一性不强,这是瘤胃内饲料蛋白质强烈降解的主要原因之     

降低反刍动物甲烷排放的研究进展

本文阐述了反刍动物瘤胃甲烷生成的生物学机制及影响反刍动物瘤胃甲烷生成的因素，并用产明了降低瘤胃甲烷产生的方法，最后对降低甲烷生成的前景作了展望。     

体外产气法评定反刍家畜饲草料营养价值的研究前景

阐述了体外产气法的原理、影响体外产气量的因素及其研究前景。     

以甜菜粕取代小麦的全混合颗粒饲料对羔羊瘤胃pH值的影响

本试验选用24只3-3.5月龄的波德代(♂)×蒙古羊(♀)和陶赛特(♂6)×蒙古羊(♀)杂交一代羔羊,按2×2×2因子设计,研究了两个营养水平下以高果胶的甜菜粕取代小麦的全混合颗粒饲料对两种羔羊瘤胃pH值的影响。结果表明,低营养水平组的pH值显著高于高营养水平组(P=0.015);食后4 h(P-0.019)、6 h(P=0.009)的pH值在营养水平和饲料间存在互作,高营养水平组,小麦组羔羊的瘤胃液pH高于甜菜粕组,而低营养水平组、甜菜粕组的pH高于小麦组;羊品种对pH值无影响。     

几种脲酶抑制剂对大豆脲酶和绵羊瘤胃微生物脲酶的抑制作用

本文研究了脲酶抑制剂乙酰氧肟酸 (AHA)、邻苯二酚、氢醌 (HQ)和硼砂对大豆脲酶和绵羊瘤胃微生物脲酶的抑制作用。结果表明 ,在浓度为 0 .0 0 0 1,0 .0 0 1,0 .0 1和 0 .1mmol/L时 ,4种脲酶抑制剂对大豆脲酶的抑制率分别为 :AHA为 6 % ,6 .2 % ,9.6 6 %和 2 9.79% ;HQ为 8.4 % ,13.0 3% ,19.79%和 4 4 .75 % ;邻苯二酚为 2 0 .34% ,19.12 % ,83.16 %和 93.78% ;而硼砂为 16 .5 5 % ,17.18% ,18.95 %和 35 .5 0 %。在相同浓度下 ,4种脲酶抑制剂对绵羊瘤胃微生物脲酶的抑制率分别为 :AHA为 9.5 8% ,14 .0 4 % ,4 1.30 %和 72 .73% ;HQ为 12 .2 1% ,39.99% ,6 4 .6 2 %和 78.87% ;邻苯二酚为 6 .0 7% ,9.36 % ,31.2 9%和 5 0 .4 4 % ;而硼砂分别为 4 .97% ,8.6 3% ,2 1.78%和 32 .0 2 %。     

瘤胃保护性蛋氨酸稳定性的研究

采用不同比例的动物油包被蛋氨酸制成瘤胃保护性蛋氨酸I(RPMetⅠ)、瘤胃保护性蛋氨酸Ⅱ(RPMetⅡ)和瘤胃保护性蛋氨酸III(RPMetⅢ)。通过人工唾液消化试验、体内尼龙袋试验和人工真胃液消化试验,检验DL蛋氨酸(DLMet)、商品过瘤胃蛋氨酸(BypassMet)和瘤胃保护性蛋氨酸(RPMetⅠ、RPMetⅡ和RPMetⅢ)的稳定性。试验结果表明,三种动物油包被蛋氨酸的稳定性均好于商品过瘤胃蛋氨酸和DL-蛋氨酸;不同比例的动物油包被对瘤胃保护性蛋氨酸稳定性的影响差异显著(P<0.05)。     

反刍动物瘤胃碳水化合物发酵研究进展

碳水化合物是反刍动物营养的一个重要组成部分，碳水化合物在反刍动物瘤胃的发酵又是其营养吸收利用的一个重要过程。本文根据国内外研究成果，全面综述了碳水化合物的分类及影响反刍动物瘤胃碳水化合物发酵的三方面因素，揭示了反刍动物对碳水化合物的吸收规律，为我国反刍动物饲养提供指导。     

Impact of cold-season grazing and supplementary feeding on rumen metabolic parameters and micro-organisms in the ewes of Gansu Alpine Fine Wool Sheep北大核心CSCD

An experiment was conducted to scientifically identify the appropriate feed for Gansu Alpine Fine Wool ewes in order to change the animals' breeding mode, which currently can only be mated at the age of 2.5 years due to insufficient nutritional supply. The experiment selected 48 12-month-old ewes and randomly divided them into group a (Diet 1), group b (Diet 2), group c (Diet 3), and a control group with no supplementary feeding. The feed test was run for 90 days. The rumen pH of groups a and b were very significantly higher (P<0.01) or group c significantly lower (P<0.05) than control group. The rumen ammonia nitrogen, protein nitrogen and total nitrogen of groups a, b and c were all higher than control group (P<0.01). The total volatile fatty acids of group a and b were all higher than the control group (P<0.01), group b significantly higher than group c (P<0.05). The molar ratio of acetic acid and propionic acid in group a was very significantly higher than control group (P<0.01), group b and c were significantly higher than control group (P<0.05). The molar ratio of butyric acid in group a was very significantly higher than group c (P<0.01). The ratio of acetic acid and propionic acid in group b was significantly lower than control group (P<0.05). The number of several rumen fiber-degrading bacteria and protozoa in groups a, b and c were very significantly (P<0.01) or significantly (P<0.05) higher than the control. In conclusion, this study shows that supplementary feeding can positively affect the rumen metabolic parameters and the number of several rumen microorganisms in Gansu Alpine Fine Wool ewes. In general, the effects of Diet 1 were the strongest, while Diet 2 also produced notable improvements. © 2018, Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Contributions of ammonia-oxidizing archaea and bacteria to nitrification in Oregon forest soils

Ammonia oxidation, the first step of nitrification, is mediated by both ammonia-oxidizing archaea (AOA) and bacteria (AOB); however, the relative contributions of AOA and AOB to soil nitrification are not well understood. In this study we used 1-octyne to discriminate between AOA- and AOB-supported nitrification determined both in soil-water slurries and in unsaturated whole soil at field moisture. Soils were collected from stands of red alder (Alnus rubra Bong.) and Douglas-fir (Pseudotsuga menziesii Mirb. Franco) at three sites (Cascade Head, the H.J. Andrews, and McDonald Forest) on acidic soils (pH 3.9–5.7) in Oregon, USA. The abundances of AOA and AOB were measured using quantitative PCR by targeting the amoA gene, which encodes subunit A of ammonia monooxygenase. Total and AOA-specific (octyne-resistant) nitrification activities in soil slurries were significantly higher at Cascade Head (the most acidic soils, pH < 5) than at either the H.J. Andrews or McDonald Forest, and greater in red alder compared with Douglas-fir soils. The fraction of octyne-resistant nitrification varied among sites (21–74%) and was highest at Cascade Head than at the other two locations. Net nitrification rates of whole soil without NH₄⁺ amendment ranged from 0.4 to 3.3 mg N kg⁻¹ soil d⁻¹. Overall, net nitrification rates of whole soil were stimulated 2- to 8-fold by addition of 140 mg NH₄⁺-N kg⁻¹ soil; this was significant for red alder at Cascade Head and the H.J. Andrews. Red alder at Cascade Head was unique in that the majority of NH₄⁺-stimulated nitrifying activity was octyne-resistant (73%). At all other sites, NH₄⁺-stimulated nitrification was octyne-sensitive (68–90%). The octyne-sensitive activity—presumably AOB—was affected more by soil pH whereas the octyne-resistant (AOA) activity was more strongly related to N availability.     

Fungal and bacterial N2O production regulated by soil amendments of simple and complex substrates

Fungal N₂O production results from a respiratory denitrification that reduces NO₃⁻/NO₂⁻ in response to the oxidation of an electron donor, often organic C. Despite similar heterotrophic nature, fungal denitrifiers may differ from bacterial ones in exploiting diverse resources. We hypothesized that complex C compounds and substances could favor the growth of fungi over bacteria, and thereby leading to fungal dominance for soil N₂O emissions. Effects of substrate quality on fungal and bacterial N₂O production were, therefore, examined in a 44-d incubation after soils were amended with four different substrates, i.e., glucose, cellulose, winter pea, and switchgrass at 2 mg C g⁻¹ soil. During periodic measurements of soil N₂O fluxes at 80% soil water-filled pore space and with the supply of KNO₃, substrate treatments were further subjected to four antibiotic treatments, i.e., no antibiotics or soil addition of streptomycin, cycloheximide or both so that fungal and bacterial N₂O production could be separated. Up to d 8 when antibiotic inhibition on substrate-induced microbial activity and/or growth was still detectable, bacterial N₂O production was generally greater in glucose- than in cellulose-amended soils and also in winter pea- than in switchgrass-amended soils. In contrast, fungal N₂O production was more enhanced in soils amended with cellulose than with glucose. Therefore, fungal-to-bacterial contribution ratios were greater in complex than in simple C substrates. These ratios were positively correlated with fungal-to-bacterial activity ratios, i.e., CO₂ production ratios, suggesting that substrate-associated fungal or bacterial preferential activity and/or growth might be the cause. Considering substrate depletion over time and thereby becoming limited for microbial N₂O production, measurements of soil N₂O fluxes were also carried out with additional supply of glucose, irrespective of different substrate treatments. This measurement condition might lead to potentially high rates of fungal and bacterial N₂O production. As expected, bacterial N₂O production was greater with added glucose than with added cellulose on d 4 and d 8. However, this pattern was broken on d 28, with bacterial N₂O production lower with added glucose than with added cellulose. In contrast, plant residue impacts on soil N₂O fluxes were consistent over 44-d, with greater bacterial contribution, lower fungal contribution, and thus lower fungal-to-bacterial contribution ratios in winter pea- than in switchgrass-amended soils. Real-time PCR analysis also demonstrated that the ratios of 16S rDNA to ITS and the copy numbers of bacterial denitrifying genes were greater in winter pea- than in switchgrass-amended soils. Despite some inconsistency found on the impacts of cellulose versus glucose on fungal and bacterial leading roles for N₂O production, the results generally supported the working hypothesis that complex substrates promoted fungal dominance for soil N₂O emissions.