模糊推理与神经网络、遗传算法在系统预测中的应用

近年来，原来并没有什么必然联系的模糊理论和人工神经网络有了较多的结合．这是由于在模糊系统设计涉及到的3个问题：第一，模糊规则的选取}第二，模糊概率函数（隶属函数）的确定；第三，模糊决策算法的决定．这在有些系统中并不是十分明确的，而人工神经网络却不需要人为干预，而只需通过实际输入、输出数据的学习即可得到其决策．但是人工神经网络也有其缺点，它不够稳定，单独使用确定度不是很高，而且神经网络中所使用的BP算法有其限制性，只能得到局部最优解． 因此，我们将模糊理论与神经网络相结合，根据其预测值与实际值的误差选取适当的权重，建立二者对预测结果的影响关系的模型，用于系统预测．在神经网络中，把BP算法和遗传算法结合起来，得到全局最优解．     

四川、山东小麦叶锈菌毒性与DNA多态性分析

本研究利用SSR标记对来自四川和山东两省的60个小麦叶锈菌株进行DNA多态性分析,同时利用小麦抗叶锈近等(单)基因系和已知所含抗叶锈基因的品系对这些菌株进行毒性分析。结果表明,菌株间相似系数较高且差异不大,为0.78～1.00,表明小麦叶锈菌所含毒性基因差异不大,菌株间亲缘关系较近。两省间/内小麦叶锈菌株的DNA多态性和毒性多态性丰富。小麦叶锈菌株的地理来源与毒性多态性有一定的相关性,而其地理来源、毒性多态性与DNA多态性不存在相关性。相同致病类型存在毒性差异,同一致病类型内遗传多态性丰富。     

攀西黑山羊群体的AFLP遗传多样性研究

 研究采用随机片段长度多态性分析了攀西地区的5个黑山羊品种（类群）的遗传多样性。结果表明：15对引物共扩增出1003条多态条带,多态频率平均为99.01%,5个黑山羊群体的遗传多样性指数变异范围为0.0136~0.2131,其中建昌黑山羊平均遗传多样性指数最高（0.1346）,攀枝花黑山羊次之（0.1329）,乐至黑山羊最低（0.1101）。5个群体遗传距离范围为0.0062~0.0281,攀枝花黑山羊与建昌黑山羊之间的遗传距离最小（DR=0.0062）,云岭黑山羊与攀枝花黑山羊之间的遗传距离次之（DR=0.0128）,乐至黑山羊与金堂黑山羊间遗传距离最大（DR=0.0281）,金堂黑山羊与其它4个类群遗传距离较大（DR=0.0173-0.0281）,说明攀枝花黑山羊与建昌黑山羊的亲缘关系最近,与云岭黑山羊的亲缘关系较近,乐至黑山羊与金堂黑山羊的亲缘关系最远,金堂黑山羊与其它4个类群遗传距离均比较远。聚类结果与群体地理分布、生态条件差异情况基本一致。     

气单胞菌外膜蛋白基因工程疫苗的研究进展

就气单胞菌外膜蛋白的基因工程亚单位疫苗、DNA疫苗、重组活载体疫苗等基因工程疫苗的研究现状、免疫方式以及不足之处进行了综述,以期为气单胞菌疫苗研制提供参考。     

Dynamics of Protein 27 of Avian Leukosis Virus and Transforming Growth Factor β2 in Lymphoid Leukosis Susceptible and Resistant Broiler Chicken Breeding Stock

The dynamics of the serum concentration of protein 27 (P27) of avian leukosis virus and transforming growth factor ₂ (TGF-₂) were compared during the period between 29 and 59 weeks of age in two flocks of broiler chicken breeding stock undergoing outbreaks of severe lymphoid leukosis (LL) associated with persistent high mortality (susceptible) and in another two flocks of breeding stock with the presence of avian leukosis virus in association with low mortality due to LL (resistant). The average mean concentration of serum P27 in the LL-susceptible flocks was significantly higher (<0.05) than that in the LL-resistant flocks in six out of seven samplings performed at 5-week intervals, between 29 and 59 weeks of age. The peak in the average rise of serum P27 in the LL-resistant flocks (309 pg/ml) was associated with the highest level of TGF-₂ (1282 pg/ml) among all flocks and at all sampling times. The significance of TGF-₂ in inhibition of lymphoid tumour development is discussed.     

鹅肥肝形成的分子机理研究进展

鹅肥肝同鲟鱼翅酱、黑菌(块菰)被西方人誉为世界三大美食珍品。本文综述了近来年鹅肥肝形成的生化机理。不同鹅种产肝性能差异的原因，可能在生化及分子标记方面的研究进展。     

Genetic association between different criteria to define sexual precocious heifers with growth,carcass, reproductive and feed efficiency indicator traits in Nellore cattle using genomic information

The aim of this study was to estimate genetic parameters for different precocious calving criteria and their relationship with reproductive, growth, carcass and feed efficiency in Nellore cattle using the single‐step genomic BLUP. The reproductive traits used were probability of precocious calving (PPC) at 24 (PPC24), 26 (PPC26), 28 (PPC28) and 30 (PPC30) months of age, stayability (STAY) and scrotal circumference at 455 days of age (SC455). Growth traits such as weights at 240 (W240) and 455 (W455) days of age and adult weight (AW) were used. Rib eye area (REA), subcutaneous fat thickness (SFT), rump fat thickness (RFT) and residual feed intake (RFI) were included in the analyses. The estimation of genetic parameters was performed using a bi‐trait threshold model including genomic information in a single‐step approach. Heritability for PPC traits was moderate to high (0.29–0.56) with highest estimates for PPC24 (0.56) and PPC26 (0.50). Genetic correlation estimates between PPC and STAY weakened as a function of calving age. Correlation with SC455, growth and carcass traits were low (0.25–0.31; ?0.22 to 0.04; ?0.09 to 0.18, respectively), the same occurs with RFI (?0.09 to 0.08), this suggests independence between female sexual precocity and feed efficiency traits. The results of this study encourage the use of PPC traits in Nellore cattle because the selection for such trait would not have a negative impact on reproductive, growth, carcass and feed efficiency indicator traits. Stayability for sexual precocious heifers (PPC24 and PPC26) must be redefined to avoid incorrectly phenotype assignment.     

利用微卫星标记对宁强矮马和蒙古马遗传多样性的研究

通过8个微卫星位点的多态性检测对宁强矮马和蒙古马共83个个体进行了遗传多样性分析。计算各微卫星位点的等位基因频率、有效等位基因数(Ne)、多态信息含量(PIC)、杂合度(H)和F统计量。结果表明:8个微卫星座位中HMS2变异最大,HTG6变异最小;蒙古马的Ne、PIC、H的平均值均高于宁强马;总群体的平均遗传分化系数Fst为0.017(P<0.01),群体内近交系数Fis为0.171(P<0.01)。说明蒙古马和宁强矮马虽外形和性能上有很大差异,但在品种形成和进化上有着较近的遗传关系。     

生长激素基因多态性与生产性能关系的最新研究

生长激素是一种具有广泛生理功能的蛋白肽激素,尤其对动物的生长发育具有重要作用。研究GH基因功能区的突变对其蛋白功能的影响,以及对哺乳动物生长发育的影响,具有重要的理论意义和实践意义。因此在生产中探讨GH基因多态性与生产性能的关系,从而达到提高动物生产水平的目的,成为人们关注的重要课题。     

Short communication: investigation of the feasibility of genomic selection in Icelandic Cattle

Icelandic Cattle is a local dairy cattle breed in Iceland. With about 26,000 breeding females, it is by far the largest among the indigenous Nordic cattle breeds. The objective of this study was to investigate the feasibility of genomic selection in Icelandic Cattle. Pedigree-based best linear unbiased prediction (PBLUP) and single-step genomic best linear unbiased prediction (ssGBLUP) were compared. Accuracy, bias, and dispersion of estimated breeding values (EBV) for milk yield (MY), fat yield (FY), protein yield (PY), and somatic cell score (SCS) were estimated in a cross validation-based design. Accuracy (r^) was estimated by the correlation between EBV and corrected phenotype in a validation set. The accuracy (r^) of predictions using ssGBLUP increased by 13, 23, 19, and 20 percentage points for MY, FY, PY, and SCS for genotyped animals, compared with PBLUP. The accuracy of nongenotyped animals was not improved for MY and PY, but increased by 0.9 and 3.5 percentage points for FY and SCS. We used the linear regression (LR) method to quantify relative improvements in accuracy, bias (Δ^), and dispersion (b^) of EBV. Using the LR method, the relative improvements in accuracy of validation from PBLUP to ssGBLUP were 43%, 60%, 50%, and 48% for genotyped animals for MY, FY, PY, and SCS. Single-step GBLUP EBV were less underestimated (Δ^), and less overdispersed (b^) than PBLUP EBV for FY and PY. Pedigree-based BLUP EBV were close to unbiased for MY and SCS. Single-step GBLUP underestimated MY EBV but overestimated SCS EBV. Based on the average accuracy of 0.45 for ssGBLUP EBV obtained in this study, selection intensities according to the breeding scheme of Icelandic Cattle, and assuming a generation interval of 2.0 yr for sires of bulls, sires of dams and dams of bulls, genetic gain in Icelandic Cattle could be increased by about 50% relative to the current breeding scheme.