天然草原青干草对农区洼地绵羊生长、屠宰性能和经济效益的影响

本试验选取4月龄洼地绵羊公羊27只,平均体重(20±0.50) kg,按随机区组原则分为3组,每组9只,以研究天然草原青干草对农区洼地绵羊生长性能、屠宰性能和经济效益的影响。试验Ⅰ组饲喂天然草原青干草,试验Ⅱ组饲喂青贮玉米秸和花生秧,试验Ⅲ组饲喂青贮玉米秸和苜蓿,饲养试验期105 d,其中预试期15 d,正试期90 d。结果表明,3个试验组间的总增重和平均日增重差异不显著;料重比试验Ⅰ组与试验Ⅱ组相比差异不显著,但试验Ⅰ组比试验Ⅱ组降低4.55%,与试验Ⅲ组相比差异显著(P<0.05),显著降低11.29%;3个试验组间体高、体长和胸围增加值差异不显著;屠宰率试验Ⅰ组比试验Ⅱ组提高1.22%,比试验Ⅲ组降低2.33%,3个试验组间差异不显著;胴体净肉率试验Ⅰ组最高,为37.83%,分别比试验Ⅱ组和试验Ⅲ组提高2.97%、1.26%,3个试验组间差异不显著;肉骨比试验Ⅰ组比试验Ⅱ组提高1.56%,比试验Ⅲ组低3.35%,3个试验组间差异不显著;3个试验组的眼肌面积大小比较接近,但试验Ⅰ组最大,分别比试验Ⅱ组和试验Ⅲ组大0.57%、7.30%;试验Ⅰ组盈利额最大,为492.15元,分别比试验Ⅱ组和试验Ⅲ多41.31和150.74元。综合研究表明,天然草原青干草对农区洼地绵羊的生长性能和屠宰性能都有促进作用,且能够提高肉羊养殖的经济效益。     

不同杂交组合黔东花猪屠宰性能及肉质性状测定

[目的]测定不同杂交组合黔东花猪的胴体性能和肉质性状,筛选优良黔东花猪杂交组合.[方法]对约克夏(Y)×皮特兰(P)×太湖猪(T)×黔东花猪(H)组合(YPTH)、巴克夏(B)×太湖猪(T)和黔东花猪(H)组合(BTH)、巴克夏(B)×皮特兰(P)×太湖猪(T)×黔东花猪(H)组合(BPTH)及巴克夏(B)×杜洛克(D)×太湖猪(T)×黔东花猪(H)组合(BDTH)等4种杂交猪分别进行屠宰,测定分析其胴体性能和肉质性状.[结果]YPrH、BTH、BDTH和BPTH杂交猪屠宰率分别为76.72%、76.67%、76.94%和81.24%;瘦肉率分别为55.58%、42.00%、46.29%和50.92%;平均背膘厚分别为3.31、4.00、3.37和3.45 cm;眼肌面积分别为60.68、46.67、46.80和53.56 cm2;大理石纹分别为3.67、3.50、3.50和3.50;系水力分别为89.33%、83.00%、76.70%和69.09%;剪切力分别为0.49、0.51、1.12和0.62 kg.脂肪酸含量分析结果表明,4种杂交猪肉的嫩度、多汁性及风味等食用性状均较佳.其中,YPTH杂交猪具有较高的瘦肉率和较大的眼肌面积,系水力较高,剪切力较小,肌肉谷氨酸含量高达107.72 mg/g.[结论]以黔东花猪(H)为母本组配的YPTH杂交猪胴体品质和肉质性状优于BTH、BDTH和BPTH杂交猪,可作为建立含有黔东花猪血缘的商品杂交猪配套系开发利用.     

全自动玉米秧苗移栽机的研制与试验

为了克服人工移栽劳动强度大、作业效率低、移栽质量差的缺点,该文研制了一种全自动玉米秧苗移栽机。设计了全液压驱动系统和以PLC为核心模块的自动控制快速上秧装置,可实现整册纸筒自动取苗,数字识别无苗纸筒并剔除,有苗纸筒带式水平和针刺带垂直输送,夹持圆盘可完成零速投苗栽植。该机与破茬开沟、垄型整理、滤水覆土有机结合,可完成全部移栽过程。田间试验结果表明,当机组前进速度为2.5～3.0 km/h、理论株距为22 cm时,移栽深度合格率为87.5%,株距合格率为93.2%,苗株直立度合格率为91.2%,能够满足玉米纸筒苗移栽的农艺要求。该机是实施玉米纸筒秧苗移栽新型农艺技术的机械化载体,可显著提高玉米纸筒秧苗移栽作业的标准化、机械化和自动化程度。     

磨粒流加工中单颗磨粒冲击的有限元分析

为了研究热泵烤烟的系统特性,并为工程应用推广提供有价值的参考,该文设计了一种新型的热泵烤烟系统,对热泵烤烟进行了试验研究。当烤房内鲜烟装载量为2 432?kg时,压缩机的最大功率为12.6?kW,系统制热系数达到了3.25,整个过程的除湿能耗比为2.42?kg/（kW·h）。最后对热泵烤烟和燃煤烤烟的经济性进行了比较,结果显示得到1?kg干烟热泵的烘烤成本为2.12元,而燃煤的烘烤成本为2.97元。与燃煤烤烟相比,热泵烤烟具有明显的节能优势和社会经济效益。     

草鱼出血病病毒血凝作用及影响因素

为了探明草鱼出血病病毒的血凝作用及其影响因素，应用血凝试验对此进行了测定，结果表明：病毒只对鸡红细胞引起高滴度凝集，这种凝集能被特异性抗血清所抑制；血凝的适宜pH为5.5-7.0,2%的氯化钠为较适宜的稀释液，血凝活性以在37℃温度条件下最好；出血病病鱼肠道的凝集价量高；醛化的鸡红细胞的4℃下保存一年多仍具有新鲜红细胞表面受体活性，从而使草鱼出血病的HA和HI试验更具有稳定性和广泛的实用性，建立了一种快速诊断草鱼出血病的方法。     

复方中药对断奶獭兔生长性能、营养物质表观消化率、免疫功能及屠宰性能的影响

本试验旨在研究不同水平的复方中药对断奶獭兔生长性能、营养物质表观消化率、免疫功能及屠宰性能的影响.将70只60日龄断奶仔獭兔随机分为7组,每组5个重复,每个重复2只.Ⅰ组为空白对照组,饲喂基础日粮;Ⅱ组为抗生素对照组,饲喂在基础日粮中添加抗生素(含50 mg/kg杆菌肽锌、10 mg/kg硫酸黏杆菌素)的日粮;Ⅲ、Ⅳ、Ⅴ、Ⅵ、Ⅶ组为中药试验组,分别饲喂在基础日粮中添加1%、2%、3%、4%、5%复方中药的日粮.预试期7 d,正试期45 d.结果表明:①Ⅳ组平均日增重显著高于Ⅰ、Ⅱ、Ⅲ组(P< 0.05),料重比显著低于其他各试验组(P< 0.05).②在干物质表观消化率上,Ⅳ组显著高于Ⅰ、Ⅱ组(P< 0.05),Ⅶ组显著高于Ⅰ组 (P< 0.05);在粗纤维表观消化率上,Ⅳ组极显著高于Ⅰ组(P< 0.01),Ⅶ组显著高于Ⅰ组(P< 0.05);在中性洗涤纤维表观消化率上,Ⅳ组极显著高于Ⅰ组(P< 0.01),显著高于Ⅱ、Ⅲ、Ⅴ、Ⅶ组(P< 0.05);在酸性洗涤纤维表观消化率上,Ⅳ组显著高于Ⅰ、Ⅱ、Ⅴ、Ⅶ组(P< 0.05);在粗蛋白质表观消化率上,Ⅳ组显著高于Ⅰ、Ⅱ组(P< 0.05).③各试验组间免疫球蛋白(IgG、IgA、IgM)含量差异均不显著(P> 0.05);Ⅳ组脾脏指数显著高于Ⅰ、Ⅱ、Ⅲ、Ⅴ组(P< 0.05).④各试验组间屠宰率、半净膛屠宰率、全净膛屠宰率差异均不显著(P> 0.05).综上所述,日粮中添加复方中药和抗生素都可提高断奶獭兔生长性能、营养物质表观消化率、免疫功能及屠宰性能,且添加2%复方中药效果最好.     

基于焦油炉内裂解的生物质气化特性试验

目前生物质气化炉推广应用过程中最主要技术问题是气化炉的原料适应性差、气化气中焦油含量高、产气热值低等。该文提出一种新型的焦油炉内裂解生物质气化炉,通过内置的U型管导气结构及其中填充多孔陶瓷蓄热材料以期促进气化气中携带焦油的裂解。试验研究表明,使用含水率12.3%的麦秸压块原料,其气化气中焦油含量显著降低至0.02～0.06g/m3,平均气化效率可达到61.9%,气化气平均低位热值达到5.0MJ/m3,即,该气化炉的新型结构能够显著降低气化气中的焦油含量,提高气化气热值,提升气化炉的产气品质。     

Soil C and N changes under tillage and cropping systems in semi-arid Pacific Northwest agriculture

Soils in semi-arid regions are highly susceptible to soil organic matter (SOM) loss when cultivated because of erratic yield, removal of crop residue for feed or fuel, uncontrolled soil erosion, and frequent fallowing to increase water storage. It is important to quantify the effect of each factor to be able to identify agoecosystems that are sustainable and recognize the management practices that best sequester C in soil. We identified changes in SOM in long-term experiments, some dating from the early 1900s, by evaluating tillage and crop rotation effects at several locations in semi-arid regions of the US Pacific Northwest. The major factors influencing changes in organic C and N were the frequency of summer-fallow and the amount of C input by crop residue. Soil erosion was low in long-term studies, but even limited soil loss can have a substantial impact on C and N levels if allowed over many years. Yearly crop production is recommended because any cropping system that included summer-fallow lost SOM over time without large applications of manure. We conclude that most of the SOM loss was due to high biological oxidation and absence of C input during the fallow year rather than resulting from erosion. Decreasing tillage intensity reduced SOM loss, but the effect was not as dramatic as eliminating summer-fallow. Crop management practices such as N fertilization increased residue production and improved C and N levels in soil. SOM can be maintained or increased in most semi-arid soils if they are cropped every year, crop residues are returned to soil, and erosion is kept to a minimum. SOM loss may be more intense in the Pacific Northwest because fallowing keeps the soil moist during the summer months when it would normally be dry. Our experiments identify two primary deficiencies of long-term studies to measure C sequestering capability: (1) soil C loss can be partitioned between erosion and biological oxidation only by estimation, and (2) C changes occurring below 30 cm in grassland soils cannot be quantified in many instances because samples were not collected.     

主动旋转集行式清秸装置设计与试验

针对东北地区在秸秆全量粉碎还田条件下玉米免耕播种作业时,被动分茬式清秸装置清秸率低,主动条旋式清秸装置草土混埋造成出苗率低的问题,该研究设计了一种主动旋转集行式清秸装置,首先通过理论分析与参数计算确定了清秸弹齿关键部件结构和工作参数。进一步运用土槽试验的方法,选取机组前进速度、清秸弹齿转速和清秸弹齿渗透量为试验因素,以种带清秸率为试验指标,进行二次旋转正交组合试验,建立了试验指标与影响因素回归模型,确定清秸装置最优作业参数组合为机具前进速度1.4 m/s,清秸弹齿转速400 r/min,弹齿渗透量19 mm。并通过田间试验对该装置作业性能进行验证。试验结果表明,最优参数组合下,20 cm宽度种带清秸率为98.3%,平均作业功率为605 W,满足东北地区玉米免耕播种作业农艺和技术要求。该研究可为免耕作业机具清秸装置设计提供参考。     

Influence of On‐farm pig Salmonella status on Salmonella Shedding at Slaughter

The risk of Salmonella shedding among pigs at slaughter with regard to their previous on‐farm Salmonella status was assessed in a group of pigs from a farm from NE of Spain. A total of 202 pigs that had been serologically monitored monthly during the fattening period and from which mesenteric lymph nodes (MLN) and faecal (SFEC) samples were collected at slaughter for Salmonella isolation were included. A repeated‐measures anova was used to assess the relationship between mean OD% values during the fattening period and sampling time and bacteriology on MLN and SFEC. Pigs were also grouped into four groups, that is pigs seronegative during the fattening period and Salmonella negative in MLN (group A; n = 69); pigs seronegative during the fattening period but Salmonella positive in MLN (B; n = 36); pigs seropositive at least once and Salmonella positive in MLN (C; n = 50); and pigs seropositive at least once but Salmonella negative in (D; n = 47). Pigs shedding at slaughter seroconverted much earlier and showed much higher mean OD% values than non‐shedders pigs. The proportion of Salmonella shedders in groups A and D was high and similar (26.1% and 29.8%, respectively), but significantly lower than that for groups B and C. The odds of shedding Salmonella for groups B and C were 4.8 (95% CI = 1.5–15.5) and 20.9 (3.7–118) times higher, respectively, when compared to A. It was concluded that a large proportion of Salmonella seronegative pigs may shed Salmonella at slaughter, which would be likely associated to previous exposure with contaminated environments (i.e. transport and lairage). For pigs already infected at farm, the likelihood of shedding Salmonella was much higher and may depend on whether the bacterium has colonized the MLN or not. The odds of shedding Salmonella spp. were always much higher for pigs in which Salmonella was isolated from MLN.