UHPLC-Q/TOF MS结合HPLC-DAD定性和定量分析硫酸黏菌素可溶性粉中的未知添加物

定性和定量分析一批兽药硫酸黏菌素可溶性粉中的未知添加物。照《中国兽药典》2010年版一部对该批检品用微生物检定法进行含量测定时,发现该样品的抑菌圈为虚圈,用薄层色谱鉴别该样品,未显示与标准品溶液一致的主斑点,怀疑该样品中有处方外非法添加物。采用超高效液相色谱-四级杆-飞行时间质谱(UHPLC-Q/TOF MS)对该样品进行筛查,发现疑似添加物,并使用液相色谱-二极管阵列检测(HPLC-DAD)法进行了双重确证和含量测定。该样品中非法添加物确证为磺胺氯达嗪和甲氧苄啶,添加量分别为58.5 mg/g和13.4 mg/g。本研究通过建立筛查方法为监管部门提供技术支撑,通过分析非法添加物的可能原因为打击兽药处方外非法添加提供了思路。     

Microbial protein formation of different carbohydrates in vitro

The aim of this study was to investigate the microbial protein yield of different pure carbohydrates to contribute to a more precise prediction of the microbial protein formed in the rumen. In a first experiment, sucrose, wheat starch, microcrystalline cellulose and citrus pectin were incubated for 8 and 24 hr in the modified Hohenheim gas test (HGT) system (3 runs × 2 syringes) including gas production, ammonia and short‐chain fatty acid concentration measurements. Ammonia values were used for estimation of the microbial protein formation. In a second experiment, the same substrates were incubated for 96 hr in the HGT system (2 runs × 3 syringes) and gas production was measured after 2, 4, 6, 8, 12, 16, 24, 30, 36, 48, 60, 72 and 96 hr of incubation to obtain the fermentation kinetics and the time of half‐maximal gas production (t_1/2) of the substrates. The substrates differed considerably in their fermentation kinetics, and therefore, comparison on the basis of t_1/2 was chosen as the most meaningful. At t_1/2, microbial protein yield [g/kg dry matter] was higher for cellulose than for sucrose and pectin and higher for starch than for sucrose. The microbial protein expressed in g/L gas production was higher for starch and cellulose than for sucrose and pectin at t_1/2. Effects of carbohydrates related to ruminal pH may remain undetected in in vitro trials.     

Variation in mammal species richness and relative abundance in the Karoo§

Understanding how climate change and land transformation may impact the distribution and diversity of wildlife species requires landscape-level foundational biodiversity surveys. The Karoo BioGaps Project aims to provide such data and to support the scientific assessment for shale gas development projects in the Karoo basin. In this paper we present the findings of the BioGaps mammal survey, which recorded medium and large mammals across twenty-five 1 km × 1 km sampling sites within the proposed fracking footprint using camera trapping techniques. We use sample rarefaction curves, non-parametric species richness estimators and non-metric multidimensional scaling plots to explore both species richness and community structure. We also used a generalised linear model to investigate how species diversity varies with both site-specific and landscape-level predictors. A total of 38 species were recorded at the majority of sites. Longitude (z = 4.018, p = 0.0005) emerged as the best predictor of species diversity across the study area, which we suggest is linked to the clear east–west aridity gradient. Together these results reveal the cosmopolitan distribution of the mammal taxa in the Karoo and could be used to inform decision-making linked to mining activities in the area.     

In vitro fermentation characteristics of different carbohydrate sources in two dog breeds (German shepherd and Neapolitan mastiff)

Few studies have been published on the normal intestinal biota of canines unlike the wealth of information regarding livestock animal species. The in vitro gas production technique (IVGPT) including measurements of accumulating gas during fermentation and end‐product determinations allows obtaining a complete picture of microbial activity kinetics. The aim of this study was to study the in vitro fermentation characteristics of different carbohydrate sources using inocula from two dog breeds (German Shepherd and Neapolitan mastiff). Faeces sampled from rectum of two GS and NM adult dogs, fed the same dry food, were used as inocula. The samples, diluted and filtered, were incubated at 39 °C under anaerobic condition with nine substrates different for carbohydrate composition (rice, corn, potato, spelt, pure cellulose, beet pulp, wheat bran, inulin and fructo‐oligosaccharide). Gas production was recorded 17 times using a manual pressure transducer. After 48 h, the fermentation was stopped and fermenting liquor was analysed for pH and volatile fatty acids (VFA). Organic matter digestibility (OMD) was calculated as difference after burning the residuals. OMD, gas production and end‐products were significantly correlated with chemical composition of substrates, in particular carbohydrate fractions (total dietary fibre and starch), confirming the effectiveness of the IVGPT in evaluating dog feeds. Concerning the comparison between breeds significant differences (p < 0.01) were found for OMD, gas production, fermentation kinetic parameters and end‐products, suggesting a different pathway of fermentation and consequently, a different anaerobic population.     

甘肃天祝牧区白牦牛乳脂肪中脂肪酸的分析

以甘肃天祝地区3个牧场所产的白牦牛乳为研究对象,采用气相色谱-质谱联用检测方法,测定3个牧场所产白牦牛乳中脂肪酸含量,比较在枯草期、枯草末期、返青期、青草期4个时期及不同胎次的白牦牛所产牦牛乳中脂肪酸的构成及含量.结果表明:3个牧场白牦牛乳中乳脂肪酸含量差异不显著(P＞0.05);1～5胎次母白牦牛乳中脂肪酸含量差异不显著(P＞0.05).枯草期、枯草末期、返青期、青草期4个时期白牦牛乳中饱和脂肪酸(SFA)、不饱和脂肪酸(USFA)含量比值分别为1.86、1.75、1.62、1.32.随着气温的升高及牧草的成熟,白牦牛乳中饱和脂肪酸含量逐渐降低,而不饱和脂肪酸的含量逐渐升高.     

Investigation of the Role of Androstenedione-19-oic Acid in the Presence of 19-Norandrostenedione in Intact Male Horse Plasma Using Liquid Chromatography–Tandem Mass Spectrometry

A liquid chromatography–tandem mass spectrometry method was developed to confirm the presence of androstenedione-19-oic acid in intact male equine plasma and to show the source of 19-norandrostenedione in equine plasma. Androstenedione-19-oic acid was recovered from acidified plasma by liquid–liquid extraction using methyl tert-butyl ether and separated on an Ace 5 C₈ column. A triple quadrupole mass spectrometer was used to detect the analytes in negative electrospray ionization mode. Limits of detection, quantification, and confirmation of the method were 0.1, 0.5, and 1.0 ng/mL, respectively. The linear dynamic range of quantification was 0.5–50 ng/mL. The presence of androstenedione-19-oic acid was confirmed in all plasma samples obtained from intact male horses but not those from gelded and female horses; the average concentration was 3.1 ± 1.6 ng/mL, suggesting androstenedione-19-oic acid is an endogenous compound only in intact male horse plasma samples. The conversion of androstenedione-19-oic acid to 19-norandrostenedione in equine plasma was demonstrated by spiking androstenedione-19-oic acid into blank plasma and monitoring the generation of 19-norandrostenedione and its increase in concentration during storage. Results indicated that androstenedione-19-oic acid was readily converted into 19-norandrostenedione; the higher the storage temperature, the faster the conversion. The conversion was not affected by the types of plasma samples collected from gelded and female horses or by anticoagulants used in blood collection to harvest plasma. Compared with other matrices such as water, methanol, and phosphate-buffered saline, the conversion of androstenedione-19-oic to 19-norandrostenedione in equine plasma was faster, suggesting that there is an unknown factor(s) in equine plasma that enhances the conversion.     

A model to assess the use of caecal and faecal inocula to study fermentability of nutrients in rabbit

An in vitro gas production trial was conducted using 10 Hyla rabbits to evaluate the use of caecal and faecal inocula in fermentability studies. Caecal content (CI) and hard faeces (FI) were used as inocula. Six legume and six cereal concentrates were used as substrates. Gas production was recorded 19 times at 2–24 h intervals throughout fermentation (120 h). The fermentation characteristics (degraded organic matter, OMd; potential gas production, A; volatile fatty acid, VFA; ammonia, NH₃) were measured by testing the inoculum and substrate (legumes vs. cereals). The inocula were different (p < 0.01) in OMd (818.2 vs. 799.4 g/kg OM for CI and FI respectively), A (255.0 vs. 267.1 ml/g OM), total VFA (67.3 vs. 53.2 mmol/g OM) and NH₃ content (21.2 vs. 19.8 mmol/l). Moreover, the significant differences in the (acetate + propionate)/butyrate ratio (5.02 vs. 4.09 for CI and FI respectively, p < 0.01) and in the branched chain proportion (isobutyrate + isovaleriate)/total VFA (0.044 vs. 0.031, p < 0.01) indicate that the inocula differed in fermenting legumes or cereals, but the equations for estimating caecal fermentation characteristics from those of faeces showed R² values from 0.673 to 0.975 (p ≤ 0.01). Our results confirm that in vitro fermentation characteristics of faeces were highly related to those of caecal content.     

通过式固相萃取-高效液相色谱-串联质谱法测定牛乳和乳粉中4种类固醇激素

建立通过式固相萃取-高效液相色谱-串联质谱法同时测定牛乳和乳粉样品中4 种类固醇激素的方法,采用内标法定量,样品用乙腈提取,经PRiME HLB固相萃取小柱净化,采用Acquity BEH C18色谱柱（2.1 mm×100 mm,2.5 μm）分离,乙腈和水作为流动相,使用电喷雾离子源负离子模式检测。结果表明：4 种类固醇激素在质量浓度0.2～100.0 ng/mL范围内线性关系良好,检出限为0.4～2.0 μg/kg,定量限为0.8～4.0 μg/kg;在牛乳基质中加标回收率为87.7%～110.8%,相对标准偏差为0.85%～4.56%,在乳粉基质中加标回收率为89.2%～107.4%,相对标准偏差为1.22%～4.22%;该方法分析速度快、灵敏度高,可用于牛乳和乳粉中4 种类固醇激素的定性及定量分析。     

电感耦合等离子体质谱仪测定乳粉中铅的检出限方法优化

对电感耦合等离子体质谱法检测铅的检出限进行研究,通过对实验过程中所用器皿、试剂等因素进行分?析,建立超声清洗处理方式,有效降低空白值,使电感耦合等离子体质谱仪法测定乳粉中铅的检出限由0.02 mg/kg降?低到0.005 mg/kg。当铅的添加水平为0.005～0.015 mg/kg时,样品的加标回收率为86.9%～119.0%,相对标准偏差为?3.1%～12.3%,满足方法学验证要求,说明了整体方案的可行性。降低检出限后的方法适用于乳粉中铅的检测。     

添加三聚氰胺对高粗料日粮短期人工瘤胃发酵理化指标的影响

为研究三聚氰胺对瘤胃微生物发酵的影响,试验采集西门塔尔×鲁西黄牛瘤胃液,以高比例粗饲料为底物,采用短期人工瘤胃发酵产气装置,分析评价了不同剂量三聚氰胺(0、6、18、54、162、486 mg/kg)对氨态氮、氨基酸态氮、干物质产气量、挥发性脂肪酸、气体组分的影响。结果表明:三聚氰胺可减少高粗料日粮瘤胃发酵总挥发性脂肪酸的产生,并且有提高乙酸与丙酸比值的趋势(P>0.05)。高浓度的三聚氰胺(486 mg/kg)能显著提高氨态氮的浓度(P<0.05)。三聚氰胺的添加对干物质产气量影响不大,但可使甲烷产量提高8.0%～41.7%。综上所述,以高粗饲料日粮为发酵底物时,三聚氰胺添加对瘤胃的发酵并没有产生显著不利影响,但可提高甲烷产生量,从而降低饲料能量的转化效率。