奶牛杂交群体及其遗传评估的模拟研究

为验证在奶牛杂交群体中将品种组成和杂合度作为协变量的遗传评估理论,为奶牛杂交模式选择和杂交群体遗传评估等实际问题提供理论依据,结合我国奶业现状,本研究模拟了在低产荷斯坦牛群引入法系蒙贝利亚牛、德系西门塔尔牛进行杂交,采用随机交配和三品种轮回杂交模式、群体世代重叠17年的繁育过程.群体杂合度在第7年后趋于平衡,轮回杂交模式的群体杂合度高于随机交配.经过杂交,原中低产荷斯坦牛群体在产奶性能、生长性能方面都有进展,轮回杂交提高幅度相对略高.此外,利用品种效应和杂合度效应剖分杂种优势,采用单性状和多性状动物模型对模拟群体进行遗传评估,效果基本一致,都可以很好地用于杂交群体的遗传评估.结果表明,对荷斯坦牛中低产群体进行杂交,可实现生产性能和效益的提高,回归模型可用于多元群体的遗传评估.     

LDSO: a program to simulate pedigrees and molecular information under various evolutionary forces

Simulations are a major tool to evaluate new statistical methods and optimize experimental designs in the genomic era. However, this can only be achieved when the simulations are close enough to reality, as well as diverse enough to be realistic. For mapping studies, it is thus critical to re-create as much as possible the forces generating linkage (mutation, random drift, changes in population sizes, selection and pedigree structure) and the mechanisms producing trait genetic architecture (additivity, dominance, epistasis). We present here a computer program (ldso) simulating these phenomena. Optional outputs provide statistics on the linkage disequilibrium (LD) structure and the identity by descent between chromosomal segments, facilitating further data analyses. Furthermore, ldso enables the simulation of genomic data in known pedigrees, which sticks as precisely as possible to recent population history and structures of the long-range LD, allowing optimization of fine-mapping strategies.     

A simulation model for predicting the voluntary feed intake of a growing pig

Abstract

The main goal of this simulator is to predict voluntary feed intake based on the effects of temperature and stocking density. The model indicates the limiting factors relative to diet (protein, energy or ash), housing environmental conditions and stocking density. The concepts of compensatory protein growth, correction of lipid growth, the desired feed intake to meet energy, protein and ash requirements, and influences of stocking density, genotype and sex are also introduced in this model. This study draws a flow chart and steps to predict feed intake of a growing pig to make it clear how the model works. The model simulates the outcomes of feed intake, energy and protein requirements for maintenance, the energy cost for cold thermogenesis, and protein and lipid retention on a daily basis until slaughter weight. This model was also validated by comparison with published experiments.     

Description of outcomes of experimental infection with feline haemoplasmas: Copy numbers, haematology, Coombs’ testing and blood glucose concentrations

The aim of this study was to compare blood copy, haematological and glucose values between cats experimentally infected with either Mycoplasma haemofelis (Group HF: 10 cats), ‘Candidatus M. haemominutum’ (Group HM: 3 cats) or ‘Candidatus M. turicensis’ (Group TU: 3 cats). Blood samples were collected regularly up to 85 days post-infection (DPI) for haemoplasma real-time quantitative PCR, haematology, Coombs’ testing and blood glucose measurement. Statistical analysis was performed using a general linear model (ANOVA) appropriate for a repeated measures experiment with significance set as P < 0.05. Cats in Group TU had significantly lower blood copy numbers than cats in Group HF (P < 0.001) and HM (P < 0.001). All Group HF cats developed anaemia (often severe), macrocytosis and evidence of erythrocyte-bound antibodies whereas Groups HM and TU cats did not. Group HF had significantly lower PCVs, haemoglobin concentrations and red blood cell counts, and significantly higher mean cell volumes, than Groups HM and TU. In Group HF, erythrocyte-bound antibodies reactive at 4 °C (both IgM and IgG) appeared between 8 and 22 DPI and persisted for two to four weeks, whereas those reactive at 37 °C (primarily IgG) appeared between 22 and 29 DPI and persisted for one to five weeks. In most cats antibodies appeared after the fall in haemoglobin started. Although Group TU had significantly lower glucose concentrations than Groups HF (P = 0.006) and HM (P = 0.027), mean blood glucose concentrations remained within the reference range in all groups. This study demonstrates that M. haemofelis infection, in contrast to ‘Candidatus M. haemominutum’ and ‘Candidatus M. turicensis’ infection, can result in a severe macrocytic anaemia and the development of cold and warm reactive erythrocyte-bound antibodies.     

猪传染性胸膜肺炎放线杆菌和猪圆环病毒2型二重实时荧光定量PCR检测方法的建立

以胸膜肺炎放线杆菌(App)apx ⅣA基因和猪圆环病毒2型(PCV-2)ORF2基因为靶基因,分别设计特异性引物和探针,建立App和PCV-2的二重荧光PCR方法。App引物扩增的目的片段大小为132bp,PCV-2为169bp。建立的方法可在同一反应体系中同时对App和PCV-2进行定量检测鉴别,其敏感性分别为1×101拷贝和1×100拷贝,对其他猪病病原核酸的检测为阴性。利用该方法对10份人工感染临床样品进行检测试验,其结果符合率达100%,说明该方法可用于对临床样品中App和PCV-2的检测。     

不同突扩比下空间淹没水跃的水力计算

突扩能够使局部范围内水流紊动剧烈,可以作为水利工程中消能工的一种重要方式．为了探讨突扩比对下游流体水力特性的影响规律,基于RNG k-ε紊流模型和PISO压力-速度耦合算法,采用非均匀结构网格技术,建立了三维紊流数学模型,对突扩比分别为1000,0833,0.667,0500,0333等5种空间水跃进行了多工况数值模拟,结合试验数据,计算结果量纲一化,讨论了不同突扩比大小对下游水力性能的影响,并分析了下游流速、紊动能及消能率等随突扩比的变化规律．数值计算结果表明:突扩比对下游流速、紊动能及消能率影响显著,突扩比越小,下游流速变化越显著,主流在空间内扩散愈迅速,流态转变越明显;随着突扩比的减小,紊动应力愈小,紊动能量愈小,而消能率越大;突扩水跃较典型水跃消能效果明显增强,当突扩比小于0500时,消能率增大不再显著．     

基于元共祖的基因组联合育种模拟研究

旨在将整合元共祖的一步法(single-step genomic best linear unbiased prediction with metafounders,MF-SSGBLUP)应用到基因组联合育种中,并与其他经典基因组选择方法进行比较分析。本研究使用QMSim软件模拟3个系谱相互独立的奶牛群体;分别使用广义最小二乘法(generalized least squares,GLS)和原始方法(naïve,NAI)估计不同群体间的祖先关系矩阵Γ;将MF-SSGBLUP、SSGBLUP和BLUP用于3个模拟群体的联合育种,评估各方法在遗传参数和育种值估计方面的差异。在不同遗传力下,GLS所得的Γ矩阵在对角线元素上略低于NAI法,在非对角线元素上没有明显差异,且基因组关系矩阵与基于元共祖构建的亲缘关系矩阵对角线元素相关系数(0.750~0.775)高于基因组关系矩阵与传统的亲缘关系矩阵相关系数(0.508~0.572)。MF-SSGBLUP遗传力估计值(0.138、0.140、0.297和0.298)与当代群体遗传力(0.107和0.296)的偏差小于其余两种方法(0.145、0.173、0.273和0.340),且MF-SSGBLUP估计育种值准确性(0.888~0.908)高于SSGBLUP法(0.863~0.876)和BLUP法(0.854~0.871)。表明,MF-SSGBLUP的遗传参数估计值无偏性更好,估计育种值准确性更高。根据上述模拟数据结果表明,在联合育种中,整合元共祖的基因组选择方法优于其他经典基因组选择方法。     

Obituaries

Uittreksel

Die groeifunksies benodig vir die simulasie van produksie van ‘n Themeda triandra‐grasveld met behulp van die PUTU 11 simulasiemodel is ontwikkel. Vir die ontwikkeling van die model is die veldproduksiedata van die 1980/81 groeiseisoen gebruik waarna dit suksesvol, vir drie groeiseisoene met uiteenlopende klimaatstoestande, getoets is. In die model is koolhidraatverdeling tussen verskillende plantdele gesimuleer deur van verskillende funksies vir elke groeistadium gebruik te maak. Die hipotese is gestel dat die verskillende plantdele na ‘ n gewenste massaverhouding tot die totale plantmassa streef deur die translokasie van koolhidrate. ‘n Beperkte maksimum tempo van translokasie in en uit plantdele is gestel. Die werklike translokasietempo verander sigmoidaal met die relatiewe massaverhoudingafwyking.     

非洲猪瘟病毒实时荧光定量PCR检测技术的研究与评价

根据非洲猪瘟病毒（African swine fever virus,ASFV）K205R基因序列设计合成引物及TaqMan探针,通过优化引物浓度、退火温度和Mg²⁺浓度,建立基于K205R基因的ASFV实时荧光定量PCR（real-time quantitative PCR,qPCR）检测方法。对在猪肝脏组织DNA中掺入重组质粒制备的模拟样品进行扩增来确定所建方法的实际检测效率,并将OIE推荐的基于p72的qPCR调整后作为评价该方法检测效果的对照。试验结果表明,基于K205R基因的检测方法在检测模拟样品时扩增效率要优于基于p72的方法,而且敏感性和特异性强,适用于非洲猪瘟的快速检测、监测。