家蚕母种继代选择方法对维持种性效果的验证

在家蚕母种继代蛾区的选择中,茧丝质旨标在平均数-0.5~1.0标准差范围内选择,并结合健康性指标选留高值,通过苍.海×日.月纯种6年6代的选择及旁系鉴定的验证表明,该方法能较好地保持种性,利于种性维持。     

如何做好家蚕原原种繁育过程中的种性维持

家蚕品种的种性维持,是指蚕品种固有的优良数量性状、经济性状在繁育过程中的延续。当前桑蚕种的繁育制度是三级繁育四级制种。原原种繁育既要为蚕种良繁提供生产所需要的原原种,同时也要选留母种继代,因而也担负蚕种的种性维持工作。蚕品种的种性能否保持,关系到该品种能否在蚕丝生产中发挥应有的作用及其使用寿命的长短。     

浅谈我场原原种繁育中的种性保持

<正>家蚕品种的种性保持是指蚕品种固有性状在繁育继代过程中的延续。蚕品种的种性能否保持,关系到该品种的推广使用寿命,更关乎蚕品种在蚕桑生产中的经济价值。四川省凉山州蚕种场是我省唯一的地区级选原普三级蚕种场,蚕种的繁育制度是三级繁育四级制种,在原原种繁育中既要为原种繁育提供所需的原原种,同时也要选留原原母种继代,因而担负着蚕品种的种性维持工     

原原种繁育中基础数据的采集

<正>目前,我国的桑蚕良种繁育制度是"三级繁育四级制种"。为了使蚕品种的优良性状在长期的生产繁育过程中保持并稳定下来,继代母种和原原种的选留非常关键,而选留母种继代蛾区和原原种留种蛾区的主要依据是生产过程中记录的各项调查数据,再计算出当代各项饲育成绩,以当代蛾区成绩并参照系统成绩选留留种蛾区。因此,在原原种生产繁育中要准确     

不同交配方式对家蚕种性影响

品种性状保持与其固有性、饲育环境、选择技术、交配型式、错乱混杂等因素相关,为了更好地进行种性维持,我们用原原母种进行多年季小系内异蛾区交配和多蛾区混合交配两种方法选择继代试验,调查试验成绩进行分析,其主要经济性状无显著性差异.     

家蚕母种继代蛾区选择的模糊综合评判研究

本文运用模糊数学综合评判基本原理,评价家蚕母种继代蛾区。其结果表明模糊评判法不仅表现出与现行法有较高的拟合性,且减少了由于人的大脑无法完成大信息量综合比较而造成的选择失误。给家蚕母种继代蛾区的选择提供了一个具有明确标准的方法,同时亦给计算机用于家蚕选种奠定了一定基础。     

家蚕卵色变异淘汰选择方法探讨

家蚕夏秋用推广品种夏芳×秋白，自1994年经四川省家蚕品种审定委员会审定通过以来，在四川省、重庆市等地呈规模推广，对蚕丝业健康发展作出了较大贡献。但近年来，该品种在繁育过程中，发现华系夏芳母种、原原种、原种，蛾间、蛾内出现卵色驳杂的变异现象，表现出较大比例淡颜色卵（肉色）。该类卵能正常生长发育，但孵化不整齐，严重地影响了该品种的实用经济价值。采用传统的母种继代时单一淘汰变异卵的方法，连续几年未能解决问题，在种性维持中遇到了难题，2000年代方银、朱勇等对夏芳变异卵进行了系统研究分析，在探明变异卵遗传特性的基础上，提出了选除变异卵的纯化品种性状的具体方案。     

家蚕母种继代交配方式及种性维持效果

在家蚕母种继代繁育中采用同胞交配、循环配对交配两种设计,对连续12代及F1代的成绩分析表明:两种交配方式对丝质影响不大,对品种适应性的影响较明显。循环配对交配的生命力、产茧量、生殖力较同胞交配高,因而在家蚕母种继代繁育中采用循环配对交配,能有效控制群体内近交系数极度上升,有利于提高品种适应性和发挥品种的优良性能。     

高茧层率基础品种123的选育

采用杂交与系统选育的方法,从F_3开始进行蛾区育,对入选蛾区及其个体应用茧质与丝质选育相结合的方法,茧质选择以个体为主,入选的个体对号交配,使茧层量基因尽快累加。丝质选择以蛾区为主,选择经活蛹缫丝,茧丝长的蛾区内茧层率高的个体继代。与此同时,应用天平摆动模式,使高茧层率基础品种的体质保持在较强水平,从而育成了家蚕中系品种的茧层率达到30％以上的水平。     

凉山州蚕种场家蚕品种种性维持的实践与成效

介绍了凉山州蚕种场家蚕品种种性维持的现状,分析了种性维持中存在的问题及种性变异产生的原因,并结合当地的环境条件和生产情况,在充分掌握品种遗传特性的基础上,在繁育过程中采取精细操作、防混防杂、严格原原母种谱系管理、定期进行品系鉴定与品种复壮、增加饲育蛾区数防止近亲交配等措施,使种性维持工作取得了一定的成效。     

牛MC4R基因多态性与体尺性状的相关分析

以西门塔尔牛、日本和牛、皖东黄牛、皖南牛和广丰牛为试验对象,利用PCR-RLFP技术检测牛MC4R基因1069C〉G的遗传突变,并采用SPSS软件分析MC4R基因的遗传多态性与牛体尺性状的关系。结果表明,该位点所对应不同基因型的个体,其体斜长在西门塔尔牛群体中存在显著差异,体斜长和胸围在皖东黄牛群体中存在显著差异。因此可以把MC4R基因作为肉牛生长发育的辅助选择的分子标记。     

Estimation of litter size variability phenotypes in Large White sows

The objective of this study was to obtain new phenotypes of phenotypic variability for the total number born (TNB) in pigs using the residual variance of TNB. The analysis was based on 246,799 Large White litter observations provided by Topigs Norsvin. Three animal models were used to obtain estimates of residual variance for TNB: the basic model (BM) containing fixed effects of farm–year and season and random effects of animal and permanent environmental sow, the basic model with an additional fixed effect of parity (BMP) and a random regression model (RRM). The within-individual variance of the residuals was calculated and log-transformed to obtain three new variability traits: LnVarBM, LnVarBMP and LnVarRRM. Then, (co)variance components, heritability, the genetic coefficient of variation at the standard deviation level (GCV_SDe) and genetic correlations between the three LnVar's and between the LnVar's and mean total number born (mTNB) were estimated with uni-, bi- and trivariate models. Results indicated that genetically LnVar's are the same trait and are positively correlated with the mTNB (~0.60). Thus, both traits should be included in breeding programmes to avoid an increase in TNB variability while selecting for increased TNB. Heritability of the LnVar's was estimated at 0.021. The GCV_SDe for LnVar's showed that a change of 8% in residual standard deviation of TNB could be obtained per generation. Those results indicate that phenotypic variability of litter size is under genetic control, thus it may be improved by selection.     

鲁中肉羊初生体尺体重的遗传参数估计

为估计鲁中肉羊初生重、体高、体长、胸宽、胸深、胸围和管围的遗传参数,利用2018年上半年出生的611只鲁中肉羊的初生体尺体重数据,采用AI-REML (Average information restricted maximum likelihood)算法,借助DMU软件分析以产羔数为固定效应、个体加性遗传效应为随机效应的多性状动物模型。结果表明:鲁中肉羊初生重、胸宽、胸深、体高、体长、胸围和管围的遗传力分别为0.16、0.10、0.22、0.44、0.43、0.46和0.52,各性状之间遗传相关为-0.517～0.773,表型相关为-0.197～0.503。说明鲁中肉羊初生重、胸宽和胸深为低遗传力性状,体高、体长、胸围和管围为中等遗传力性状。     

Effect of specialization on genetic parameters of studbook–entry inspection in Dutch Warmblood horses

Recent studies on data from the Dutch Warmblood Studbook (KWPN) have shown that the ongoing specialization of horses for either dressage (DH) or show jumping (JH) has led to a decreasing genetic relationship between the two subpopulations. The aim of this study was to analyse the effect of the specialization process on the genetic parameters of traits measured in the studbook–entry inspection of KWPN during the last fifteen years. Data from 18 125 DH and 23 800 JH recorded from 1998 until 2013 were used to analyse 13 traits scored in both DH and JH. Analyses were performed in a Bayesian framework. Firstly, variance components were estimated based on the whole data set. Secondly, genetic correlations between traits measured in DH or JH were estimated using bivariate analyses. Thirdly, three time periods were defined and genetic correlations between subpopulations were estimated within each period. Heritability was moderate (0.17–0.39) for both DH and JH. Genetic correlations between traits measured in DH or JH were not different from one considering the posterior standard deviation of the estimation; however, in most of the traits, a clear trend in reduction of the genetic correlation for traits expressed in DH and JH and an increase in their posterior standard deviation for recent years was observed. These results suggest that specialization could lead to differences in traits measured in DH and JH in the recent years.     

番鸭生长性状遗传参数的估测

对白羽番鸭RF系各阶段的生长性状进行表型分析和遗传参数估计。结果：各阶段的体重遗传力较高，日增重的遗传力中等，而0－70日龄料肉比和0－84日龄料肉比遗传力偏低。同时还表明，各阶段体重之间和日增重之间存在较强的正遗传相关，而各阶段日增重与料肉比之间存在不同程度的负遗传相关。生长性状遗传相关的变化范围在－0．824－0．912。     

Genetic associations between temperament and performance traits in Nellore beef cattle

The aim of this study was to estimate genetic associations between temperament and performance traits. Temperament was evaluated in yearling male and female Nellore cattle, using four traits: temperament score (TS), for assessing animals’ reactions in a corral pen (n = 25 691); movement score (MOV), for animals’ movements recorded inside the crush; crush score (CS), for animal's general reactivity inside the crush; and flight speed (FS), for the speed (in m/s) at which the animals exited the crush (n = 11 697, for the last three methods); for all the temperament traits, lower scores indicate animals with calmer temperament. Performance traits were visual scores for conformation (C), finishing precocity (P) and muscling (M) evaluated at yearlings, and average daily gain (ADG) was estimated from weaning to yearling. Bayesian inference using Gibbs sampling was applied to estimate (co)variance components and genetic and phenotypic parameters. Heritability estimates for the temperament traits ranged from 0.07 (CS) to 0.28 (FS). Genetic correlations of the temperament traits with ADG and C, P and M were negative and ranged from −0.02 to −0.31. Phenotypic correlations were negative and consistently lower than the genetic, ranging from −0.08 to −0.02. It was concluded that the temperament traits assessed had favourable genetic correlation estimates with the performance traits studied. However, indirect responses in temperament when selecting for higher ADG and visual scoring system of C, P and M, will be low.     

Variance components and heritabilities for sow productivity traits estimated from purebred versus crossbred sows

Genetic parameters were estimated for number of pigs born alive (NBA), adjusted litter weaning weight (ALWT), and the interval from weaning to first service (W2E) using 2002 purebred litter records and 14 583 crossbred litter records from a swine production unit with a defined great‐grandparent, grandparent, and parent stock genetic system structure. Estimation of (co)variance components was carried out by REML methods. Heritability estimates from this study for NBA were 0.155, 0.146, 0.145 for the purebred, crossbred, and pooled data, respectively. Heritability estimates for ALWT were 0.162, 0.195, and 0.183 for the purebred, crossbred and pooled data, respectively. Heritability estimates for W2E were 0.205, 0.239 and 0.202 for the purebred, crossbred and pooled data, respectively. Genetic correlations between NBA and ALWT were weak and positive for the three groups. The genetic correlation between W2E and ALWT were ?0.158 for the purebred Yorkshires, 0.031 for the crossbreds and 0.051 for the pooled data. The genetic correlation between W2E and NBA was ?0.027 for the purebred Yorkshires, 0.310 for the crossbreds and 0.236 for the pooled data. These similarities suggest that pooling of purebred and crossbred data may be considered, which may potentially increase the accuracy of breeding value estimates, which would result in increased genetic progress.     

Comparison of sow farrowing characteristics between a Chinese breed and three French breeds

Sow farrowing characteristics, including litter size, stillbirth, kinetics of births and piglet weight traits, were compared in 4 populations: Meishan (MS), Large White (LW), Duroc × Large White (DU × LW) and Laconie (LA). The kinetics of births was characterised by farrowing duration (FD), birth interval (BI), and farrowing irregularity, estimated by the standard deviation of BI (SDBI). The within-litter distribution of piglet birth weights was described by different traits including the mean (MBW) and standard deviation (SDBW) of birth weight. Additional characteristics of the sow were also analysed: weight at farrowing (SWF), gestation length (GEST), and birth assistance (BA). The data set included 47 MS, 605 LW, 55 DU × LW and 160 LA litters. For analyses, multivariate methods were used, including principal component analyses (PCA) and multiple factorial analyses (MFA). These methods allowed the relative importance of between-breed and within-breed variability of the correlation structure to be estimated and the homogeneity between populations (by comparison of the 4 breed correlation structures) to be investigated. Though most of the variability was observed within-breed (97%), between-breed variation appeared to be highly significant (P < 0.0001). This variation was essentially due to the Meishan breed departing from others, because of the lower weight at farrowing and, to a lesser extent, to the lower number of stillbirths and lower piglet mean and standard deviation in birth weight. Litter size did not contribute much to the variability between breeds. The rather strong correlations related to between-breed structures (r > 0.70) indicated that the correlation pattern was similar among breeds. Stillbirth was independent from litter size and appeared as closely associated with farrowing duration in the French breeds.     

Genetic analysis of reproductive performance in sows during porcine reproductive and respiratory syndrome(PRRS) and porcine epidemic diarrhea(PED)outbreaks

Background: Porcine reproductive and respiratory syndrome(PRRS) is one of the most infectious swine diseases in the world, resulting in over 600 million dollars of economic loss in the USA alone. More recently, the USA swine industry has been having additional major economic losses due to the spread of porcine epidemic diarrhea(PED).However, information regarding the amount of genetic variation for response to diseases in reproductive sows is still very limited. The objectives of this study were to identify periods of infection with of PRRS virus(PRRSV) and/or PED virus(PEDV), and to estimate the impact their impact on the phenotypic and genetic reproductive performance of commercial sows.Results: Disease(PRRS or PED) was significant(P 0.05) for all traits analyzed except for total piglets born.Heritability estimates for traits during Clean(without any disease), PRRS, and PED ranged from 0.01(number of mummies; Clean and PED) to 0.41(abortion; PED). Genetic correlations between traits within disease statuses ranged from-0.99(proportion born dead with number weaned; PRRS) to 0.99(number born dead with born alive;Clean). Within trait, between disease statuses, estimates ranged from-0.17(number weaned between PRRS and PED) to 0.99(abortion between Clean and PRRS).Conclusion: Results indicate that selection for improved performance during PRRS and PED in commercial sows is possible and would not negatively impact performance in Clean environments.     

Estimation of genetic parameters of type traits in Asturiana de los Valles beef cattle breed

Ten type traits and a final score were analysed in 5868 records of the Asturiana de los Valles beef cattle breed. Traits were grouped into two classes: (i) traits scoring skeletal and muscular development and (ii) traits scoring adjustment to the breed standard. Heritabilities were moderate to low, ranging from 0.04 to 0.26. Genetic correlations among traits were, in general, in the same direction as, but higher than, phenotypic correlations. The genetic variability shown, in general, for the analysed traits would justify the inclusion of morphological assessment in the Asturiana de los Valles beef cattle breed sire selection programme. Main characteristics of the current type classification system are criticized. The knowledge of (co)variances among type and economically important productive and reproductive traits is recommended before revision of the classification methodology.