Use of the N-alkanes to Estimate Intake, Apparent Digestibility and Diet Composition in Sheep Grazing on Stipa brevifl ora Desert Steppe

The application of n-alkane as markers to estimate herbage intake, apparent digestibility and species composition of diet consumed by grazing sheep was studied. Six local Mongolian sheep were used to determine dry matter （DM） intake, apparent DM digestibility and species composition of diet during summer, autumn and winter. Animals were orally dosed twice daily with n-alkane gelatin capsules containing 60 mg C32-alkane as an external marker. Diet composition was estimated by comparing the odd-chain n-alkanes pattern profile （C27-C31） of the consumed plant species with the n-alkanes fecal concentrations of grazing animals, using a non-negative least squares algorithm called EATWHAT software package. The alkane pair C32：C33 and C33 alkane were used to estimate DM intake and diet apparent DM digestibility, respectively. The results showed that daily dry matter intake of the sheep were 1.77, 1.61 and 1.18 kg d-1 in summer, autumn and winter, respectively. Apparent DM digestibility, crude protein （CP）, metabolizable energy （ME） and neutral detergent fiber （NDF） intake of diet consumed by sheep decreased significantly （P〈0.01） from summer to winter, with no evident changes in ADF and ADL intake. Diet composition indicated Artemisia frigida Willd was the most dominant diet component, contributed 79.68, 68.12 and 86.26% of sheep＇s diets in summer, autumn and winter, respectively. Cleistogenes songorica Ohwi and Convolvulus arnmannii Desr were the important components of the diet. Although Stipa breviflora Griseb is one of the main plant species in the study area, the sheep rarely choosed it. The study indicated that CP and ME in diet consumed by sheep were deficient in winter. Therefore, appropriate supplementation strategies should be indispensable during this period.

Productive Response of Pelibuey Sheep to Supplementation in the Stretching Season in the Dry Tropic

Sheep meat production in the dry tropics of Mexico is low in the dry season, due to lack of forage, therefore, strategic supplementation is important to avoid weight loss in animals;The research was carried out from August 15 to December 15, 2020 in order to evaluate the productive response of pelibuey sheep in confinement, fed with pangola grass hay (GH), plains grass silage (PGS) and supplemented with commercial feed (CF) in the dry season. 16 sheep of the same weight and age were used, four treatments were evaluated in them, in a completely random design;the treatments were four levels of supplement 0, 0.1, 0.2 and 0.3 kg of AC fed with HP and PGS. Sheep were dewormed at the beginning of the experiment and housed in individual cages. The variables were: dry matter intake, daily weight gain (DWG) and DM digestibility. DM consumption was different (P < 0.01), the lowest consumption was 0.364 kg in treatment 1 (T1), with a maximum of 0.684 kg in T4;WDG was different (P < 0.01), with a lower value of 0.044 kg·day-1 in T1 and a higher value of 0.112 kg in T4. The apparent digestibility of the dry matter showed a difference (P < 0.01) which varied from 45.52 to 59.15% for T1 and T4, respectively. DM intake, WL gain, and DM digestibility increased with increasing supplement level at the levels studied.

Intake and Digestibility of Native and Exotic Grasses Fed Ad libitum to Djallonke Sheep in South Benin

Native （Andropogon gayanus, Panicum maximum and Pennisetum purpureum） and exotic grasses （Brachiaria ruzi：iensis, Panieum maximum cv. C1 and T58） consumed in tropical humid zone were evaluated by estimating their voluntary intake and in vivo digestibility. The measurements were performed with 4 male Djallonke sheep （28 kg LW） fed ad libitum in metabolic cages, during a 10-days in vivo trial, preceded by a 14-days accommodation period. Each grass was studied at 3 stages of development. The samples （distributed grasses, refusals and faeces） were analysed for organic matter （OM）, crude fibre （CF）, neutral detergent fibre （NDF）, acid detergent fibre （ADF）, acid detergent lignin （ADL） and crude protein （CP） contents. Voluntary digestible organic matter intake （VDOMI） and voluntary digestible crude protein intake （VDCPI） were calculated （in g kg ^-1 LW075） as synthetic parameters to compare the grasses. The chemical composition of the distributed forages varied significantly （P 〈 0.001） between species or cultivars and development stages. After 4-5 leaves per tiller stage, CP contents decreased in all species and lowest in native species. Andropogon gayanus was the most l ignified species at any stage of development. At the end of the rainy season, Pennisetum purpureum leaves and Brachiaria ruziziensis had the highest CP. For all the grasses, CP contents were higher （and CF contents lower） in the consumed material, compared to the offered forages, showing thereby the high selectivity by the sheep. Dry matter intake, OM and CP digestibility varied greatly （P 〈 0.001） between forages and development stages with high interactions between these factors （P 〈 0.001）. Voluntary digestible organic matter intake and VDCPI were the highest （P 〈 0.05） for native Panicum maximum and Pennisetum purpureum. There was a relationship between digestibility and intake parameters, and ADL content of the grasses seems to be an important factor determining at least digestibility.

Gating system optimization of low pressure casting A356 aluminum alloy intake manifold based on numerical simulation

To eliminate the shrinkage porosity in low pressure casting of an A356 aluminum alloy intake manifold casting, numerical simulation on fi lling and solidifi cation processes of the casting was carried out using the ProCAST software. The gating system of the casting is optimized according to the simulation results. Results show that when the gating system consists of only one sprue, the fi lling of the molten metal is not stable; and the casting does not follow the sequence solidifi cation, and many shrinkage porosities are observed through the casting. After the gating system is improved by adding one runner and two in-gates, the fi lling time is prolonged from 4.0 s to 4.5 s, the fi lling of molten metal becomes stable, but this casting does not follow the sequence solidifi cation either. Some shrinkage porosity is also observed in the hot spots of the casting. When the gating system was further improved by adding risers and chill to the hot spots of the casting, the shrinkage porosity defects were eliminated completely. Finally, by using the optimized gating system the A356 aluminum alloy intake manifold casting with integrated shape and smooth surface as well as dense microstructure was successfully produced.

Three-dimensional transient numerical simulation for intake process in the engine intake port-valve-cylinder system

This paper presents a KIVA-3 code based numerical model for three-dimensional transient intake flow in the intake port-valve-cylinder system of internal combustion engine using body-fitted technique, which can be used in numerical study on internal combustion engine with vertical and inclined valves, and has higher calculation precision. A numerical simulation (on the intake process of a two-valve engine with a semi-sphere combustion chamber and a radial intake port) is provided for analysis of the velocity field and pressure field of different plane at different crank angles. The results revealed the formation of the tumble motion, the evolution of flow field parameters and the variation of tumble ratios as important information for the design of engine in-take system.

Analysis of the Heat Transfer Efficiency of an Automobile Engine under Different Grille Opening and Closing Conditions

Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.

Application of Space-time Conservation Element and Solution Element Method in Intake and Exhaust Flows of High Power Density Diesel Engine

A one-dimensional pipe flow model of single-cylinder diesel engine is established to investigate the intake and exhaust flow characteristics of diesel engine in the condition of high power density(HPD).A space-lime conservation element and solution element(CE/SE)method is used to derive the discrete equations of the partial differential equation for the intake and exhaust systems.The performance parameters of diesel engine with speed of 2100 r/min are simulated.The simulated results are in accordance with the experimental data.The effect of increased power density on charging coefficient is analyzed using a validated model.The results show that the charging coefficient is slowly improved with the increase in intake pressure,and is obviously reduced with the increase in engine speed.

Effect of Groundnut (<i>Arachis hypogaea</i>L.) Haulm and Maize Bran Mixture Supplementation on Growth and Carcass Characteristics Performance of Local Sheep Fed Pasture Hay Basal Diet

The experiment was conducted to evaluate the effect of groundnut haulm and maize bran mixture supplementations on feed intake, digestibility, body weight gain and carcass characteristics of local sheep fed hay basal diet at Salga sheep farm in Assosa district, Western Ethiopia. The experiment was laid out in a randomized complete block design (RCBD) with four treatments consisting of six blocks with four animals per block based on their initial body weight of 20.12 ± 0.05 kg (mean ± SD). Treatments comprised of feeding natural pasture hay ad libitum T1 = 0;T2 = 100% maize bran (MB);T3 = 50% MB and 50% Groundnut haulm (GNH), and T4 = 100% GNH. The amount of supplements offered was 300 g/day/animal on DM basis. The daily feed intake, daily body weight gain, feed conversion efficiency, dry matter and nutrient digestibility, and carcass characteristics parameters were measured during the experimental period. The study result indicates that the crude protein (CP) contents were 7.12% and 11.6%, and the neutral detergent fiber (NDF) contents were 67.9% and 57.5% for natural grass hay and groundnut haulm, respectively. The total DM intake was higher (P < 0.001) in T4 (941 g/day) followed by T3 (937 g/day), and T2 (934 g/day). However, the control group (T1) consumed relatively higher basal dry matter (DM) (767 g/day) as compared to all other groups. Local Sheep supplemented with T4 had significantly different (P < 0.001) FBW (33.2 vs 24.3 kg), FCE (0.17 vs 0.08) and ADG (156.2 vs 46.4 g/day) as compared to the control group. The mean DM, OM, and ADF digestibility in the control group (T1) was significantly lower than the supplemented groups (P < 0.001), but there is no significant difference between supplemented treatments (T2, T3, T4). The CP digestibility was the least in the control group (T1) than the supplemented (76 vs 85.5, 88.8 and 89.3 for T1, T2, T3 and T4, respectively). Furthermore, dressing percentage on slaughter weight and empty body weight basis and rib-eye muscle area were high for T4. Empty body weight and hot carcass weight were higher in T4 (27.5 and 15.2 kg) and T3 (25.5 and 14.1 kg) as compared to the control group (19.8 and 10.3 kg), respectively. Similar to biological performance, the economic analysis also showed that supplementation with T4 resulted in better returns compared to others. Thus, it can be concluded that supplementation in general improved animal performance. Among the supplements, T4 is biologically optimum and economically feasible.

Dose Response of Ruminal Microbial Flora and Metabolism of Sheep to Supplemental Polyacrylamide

[Objective] The paper was to test the effects of polyacrylamide(PAM) on ruminal microbial flora, activities of fibre-degrading enzymes and voluntary feed intake(VFI) of sheep. [Method] Five of 2-3 years old male Small-tail Han sheep, with body weight of(51.5±4.1) kg and fitted with permanent rumen fistula were used. By a 5×5 Latin square design, sheep were fed a basal diet supplemented with PAM at 0(control), 1.0, 2.0,3.0 and 6.0 g/kg diet, respectively. [Result] PAM supplementation affected VFI and ruminal indexes, and the peak values of them were at 2.0 g/kg diet by 17.9% for VFI, 56.6% for total bacteria, 18.3% for endocellulase, 19.4% for exocellulase and 16.5% for cellubiase( all P<0.05), respectively,compared with control. The NH3-N, protozoal counts, and the protease activity in rumen fluid were all linearly declined, but fungal counts increased linearly. No significant changes were found in pH, activities of xylanase and amylase of rumen fluid. The PCR copies of Fibrobacter succinogenes,Ruminococcus albus, Butyrivibrio fibrisolven and Selenomonas ruminantium increased to maximum of 21.4%, 22.7%, 22.6% and 20.6%(all above P<0.05), whereas these of Prevotella bryantii, Clostridium aminophilum, methanogens and microscopic counting of great coli decreased to maximum of 24.5%, 34.8%, 21.2% and 52.2%(all above P<0.05);but Salmonella bovis and Prevotella ruminicola were not affected by PAM. [Conclusion]PAM supplementation at 2.0 g/kg diet can reduce protozoa but increase bacteria, particularly those species for fibre digestion, and fungi in rumen.The effect of PAM on bacterial species was selective. These changes finally enhanced activities of enzymes for fibre digestion in rumen, and stimu-lated VFI of sheep, suggesting a potential application of PAM in ruminant production.

Multi-omics revealed the mechanism of feed efficiency in sheep by the combined action of the host and rumen microbiota

This study was conducted to investigate potential regulatory mechanisms of feed efficiency(FE)in sheep by linking rumen microbiota with its host by the multi-omics analysis.One hundred and ninety-eight hybrid female sheep(initial body weight=30.88±4.57 kg;4-month-old)were selected as candidate sheep.Each test sheep was fed in an individual pen for 60 days,and the residual feed intake(RFI)was calculated.The ten candidate sheep with the highest RFI were divided into the Low-FE group,and the ten with the lowest RFI were divided into the High-FE group,all selected for sample collection.The RFI,average daily gain and average daily feed intake were highly significantly different between the two experimental groups(P<0.05).Compared with Low-FE group,the insulin-like growth factor-1 and very low-density lipoprotein in serum and the propionate in rumen significantly increased in High-FE group(P<0.01),but the acetate:propionate ratio in rumen significantly decreased in High-FE group(P=0.034).Metagenomics revealed Selenomonas ruminantium,Selenomonas sp.and Faecalibacterium prausnitzii were key bacteria,and increased abundance of the genes encoding the enzymes for cellulose degradation and production of propionate in High-FE group.The results of proteomics and section showed the rumen papilla length and expression of carbonic anhydrase and Na^(+)/K^(+)-ATPase were significantly higher in High-FE group(P<0.05).On the other hand,the acetyl-CoA content significantly increased in the liver of High-FE group(P=0.002).The relative expression levels of insulin-like growth factor-1 and apolipoprotein A4 genes were significantly up-regulated in the liver of High-FE group(P<0.05),but relative expression level of monoacylglycerol O-acyltransferase 3 gene was significantly down-regulated(P=0.037).These findings provide the mechanism by which the collaborative interaction between rumen microbiota fermentation and host uptake and metabolism of fermentation products impacts feed efficiency traits in sheep.

The Cotton Stalk and Its Utilization as Ruminant Feed Resource in Xinjiang

Two separate experiments were carried out: the first one involved a study of the chemical and some intrinsic feed characteristics of raw cotton stalk( CS) and the efficiency of chemical,biological treatments on the improvement of the feed value of CS. CS was treated with chemical treatment by mixing 3% Ca( OH)2( CS + Ca),3% urea( CS + U),3% urea +3% Ca( OH)2( CS + Ca + U). Moreover,CS was treated with biological treatment by inoculation of either Lentinus edodes( CS + Po) or Pleurotus ostreatus( CS + Pl) or crushing CS by adding minor ingredient processed into pellet feed,samples from all treatment were analyzed for the nutrients,In vitro dry matter digestibility( INDMD) and free gossypol detoxification rate. The second investigated was the use of crushed or granulation CS as a test feed followed by voluntary feed intake and preference test with sheep. CS + Ca + U treatment can reach up the CP and IVDMD to 9% and 36%,respectively. CS + Po decreased the fiber component and improved CP content and IVDMD. The free gossypol content declined and the free gossypol detoxification rate reached more than 50%. By feeding sheep under the same level of concentrate and corn silage,the voluntary feed intake and daily weight gain in granulation group is higher than in crushing group( P < 0. 05). Crushing CS by adding minor ingredient processed into a pellet feed was best in terms of improved nutritional quality,feed intake and preference,and it was safe and practical method that can be widely used in sheep production systems,to promote the CS feed utilization in similar areas.

Responsiveness Improvement of Idling Speed Control for Automotive Using SMC

To improve the responsiveness of engine speed control to disturbances, robust controls were investigated by simulation. The intake air control system of a gasoline engine is a typical nonlinear system, and the disturbances and parameter perturbations are generally regarded as being the unstable factors with regard to engine control. In this paper, a Mean-Value Engine Model (MVEM) with disturbances and parameter perturbations is investigated using Sliding Mode Control (SMC), which is a form of variable structure control, with a view to address instability in the idle speed control process. The simulation results confirmed that, compared with a conventional PI (Proportional-Integral) controller, the stability of the idle speed for an engine that is being subjected to disturbances, parameter variations and background noise is greatly improved by the application of SMC.

地下进风系统对间接空冷塔性能的影响

削弱环境风对间接空冷塔散热器性能的不利影响,有助于其安全和经济运行。该文提出一种新型间接空冷塔地下进风系统,将空冷散热器整体布置在低于地表平面的地下空间内。建立配置地下进风系统的间接空冷塔数值计算模型,得到间接空冷塔的空气流场特性和热力特性。基于凝汽器和空冷散热器协同调节、相互制约的作用机制,采用机理模型和数值模拟相结合的方法建立排汽压力的计算模型,在此基础上计算地下进风系统的热经济性。结果表明,在4 m/s风速下,虽然迎风扇段空气流量减少14.5%,热负荷降低12.4%,但侧风扇段和背风扇段冷却空气量分别增加46.0%、8.0%,热负荷分别提升30.9%、3.2%。在高风速工况下,地下进风系统削弱环境风对排汽压力的影响,具有抵御自然大风的能力。某660 MW间接空冷机组,采用地下进风系统全年可节约标煤9554.3 t,节省燃料费1094.0万元。

喷水推进器进水流道在来流含气条件下的内部流动特性分析

为了研究喷水推进器进水流道在来流含气条件下的内部流动特性,以轴流式喷水推进器为研究对象,对喷水推进器在不同来流含气条件下进行全流域定常数值仿真,得到了不同来流含气条件下进水流道各截面气相体积分数分布特征和不均匀度变化规律.计算结果表明:在低航速区间时,进水流道内流量小、流速低,受管道几何结构影响,下部弯管处流体堆积现象明显,随着航速的升高,流量增大、流速提高,流体在上部弯管处产生流动分离,导致堆积区向上部弯管转移;在来流含气条件下,进口含气率和气泡直径的增大,会导致气液两相干涉作用变强,造成气体堆积现象加剧,影响流面的不均匀度.

泵站进水系统三维水动力特性数值模拟研究

【目的】研究泵站进水系统结构对水泵进水流场的影响。【方法】基于Fluent平台,假定水流为不可压缩湍流流体,在满足连续方程和动量方程的基础上,引入RNGk-ε紊流模型,对改造前后泵站进水系统进行了数值模拟,采用适于稳态流场的收敛速度更快的SIMPLEC算法,利用有限体积法进行空间离散求解,分析了不同断面的流场流速、流速旋角及流线分布,对比分析了改造前后泵站进水系统的水动力指标。【结果】改造方案各水动力指标均小于改造前方案,进水池流速标准差减小了6%~64%,进水管进口流速标准差降低了41%~96%,平均流速旋角减小了60%~73%,流速旋角标准差降低了59%~72%,水流流态分布趋向均匀,水泵进水条件明显改善。【结论】改造后泵站进水系统流速分布较均匀,流态趋于平稳,对减轻泵站机组汽蚀破坏有重要意义。

进气道滚流比对发动机压升率及噪声的影响

以某双喷射6缸发动机为研究对象,设计高滚流比和低滚流比2种进气道,通过三维计算流体动力学软件AVL Fire对缸内流场进行仿真,分析发动机燃烧特性,并进行台架燃烧测试和噪声测试。仿真结果表明:在转速为2800 r/min、平均有效压力为1.3 MPa工况下,相比高滚流进气道方案,低滚流气道方案的缸内第一、二个峰值滚流比分别降低了43.3%、34.9%,最大缸内平均压力降低544 kPa,最大压力升高率降低16.84%。台架试验结果表明:2种进气道的燃烧持续期相差不大,相比高滚流进气道方案,低滚流方案以曲轴转角表示的燃烧重心推迟了2.02°,燃油消耗率增大0.67%,压力升高率(压升率)降低了19.87%,发动机在频率为700~1300 Hz时的噪声约降低6.0 dB,噪声改善效果明显。

切向进气结构对径向流甲醇合成反应器传热特性影响研究

为探究切向进气结构对径向流甲醇合成反应器内催化床层传热特性的影响,通过改变径向流甲醇合成反应器内外分布筒体开孔角度,将混合气入口处普通进气方式改为切向进气,建立了θ=0°、15°、30°、45°的切向进气径向流甲醇合成反应器结构,并采用CFD软件对各角度下反应器温度场进行模拟计算。研究表明,合理的切向角度下的切向进气结构可以提高反应器内流体的混合程度,增加反应物的接触面积,增强传热,不仅能提高反应器温度分布的均匀性,还提高了反应效率和产物收率。研究发现,当θ=30°时反应器内温度场分布最为均匀。

不同剩余采食量对德新肉用细毛羊生长性能、血清生化指标、肝脏及十二指肠黏膜抗氧化能力的影响

本试验旨在研究高、中、低剩余采食量(RFI)对新疆德新肉用细毛羊生长性能、血清生化指标、肝脏和十二指肠黏膜抗氧化指标的影响。选用50只70日龄德新肉用细毛羊公羔作为试验群体,单栏饲喂114 d,其中预试期14 d,正试期100 d。根据线性回归方程筛选出RFI区间最小值和最大值分别为-0.31和+0.10 kg/d,并按照RFI>平均值+0.5标准差(SD)、平均值+0.5SD≥RFI≥平均值-0.5SD和RFI<平均值-0.5SD分为高RFI组(H-RFI组,11只)、中RFI组(M-RFI组,18只)和低RFI组(L-RFI组,13只)。试验期每20 d测定平均日增重及平均日采食量;试验期第100天,羊只屠宰后称量内脏重,测量消化道长度,并对血清中甲状腺激素、促甲状腺激素、瘦素、生长激素及肝脏和十二指肠黏膜抗氧化指标进行测定。结果表明:1)H-RFI组平均日采食量和RFI极显著高于L-RFI组和M-RFI组(P<0.01),料重比极显著高于L-RFI组和M-RFI组(P=0.01)。各组间羊只平均日增重、中期代谢体重无显著差异(P>0.05)。2)L-RFI组心脏重、脾脏重、肾脏重显著高于H-RFI组(P<0.05),头重、蹄重、肺脏重、肝脏重极显著高于H-RFI组(P≤0.01)。M-RFI组空肠重显著高于H-RFI组(P<0.05)。3)L-RFI组血清生长激素含量显著低于H-RFI组(P=0.05),血清甲状腺激素和瘦素含量极显著低于M-RFI组和H-RFI组(P<0.01)。4)肝脏抗氧化指标中,L-RFI组总蛋白(TP)含量极显著低于M-RFI组和H-RFI组(P<0.01),丙二醛(MDA)含量显著高于M-RFI组(P<0.05),谷胱甘肽过氧化物酶(GSH-Px)活性和总抗氧化能力(T-AOC)显著高于H-RFI组(P<0.05),L-RFI组和M-RFI组过氧化物歧化酶(SOD)活性显著高于H-RFI组(P=0.05)。十二指肠黏膜抗氧化指标中,M-RFI组TP含量极显著高于L-RFI组和H-RFI组(P=0.01),L-RFI组GSH-Px活性显著低于M-RFI组(P<0.05),M-RFI组过氧化氢酶(CAT)活性显著高于H-RFI组(P<0.05),M-RFI组T-AOC显著高于L-RFI组和H-RFI组(P<0.05)。由此可见,选择L-RFI的德新公羔可以有效减少饲粮消耗,并对羊只生长性能无显著影响,对德新肉用细毛羊选种选育具有较好的提升效果。

加装谐振腔的巴哈赛车进气系统设计

为了提高赛车发动机的充气效率,进而提高发动机的性能,同时兼顾安全性,对小型越野巴哈赛车的进气系统进行了设计。首先依据波动效应计算进气管直径和长度;再依据发动机原机参数在GT-Power仿真软件中建立发动机原机模型,增设谐振腔,依据谐振腔对发动机有效功率的影响,选择出最佳谐振腔直径;最后设计进气口防水部件,使赛车具备较好的防水性能,以面对越野赛道恶劣的环境。