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本研究旨在对比值性状QTL采用贝叶斯定位方法进行探讨。将两个具有正态分布的普通数量性状之比定义为比值性状。由于此类性状不服从正态分布,因此在遗传分析上不同于普通性状。利用构成比值性状的两个组分性状的线性结合,我们提出了定位比值性状数量性状位点(QTL)的最大似然法。在此基础上,进一步探索比值性状的贝叶斯定位策略。首先采用贝叶斯压缩方法估计两个组分性状的QTL参数,然后利用两个组分性状的群体均值和QTL遗传效应,产生一个关于比值性状QTL遗传效应的后验样本,通过对这个后验样本的统计分析,来推断比值性状的QTL。模拟研究表明:新方法表现出比似然法更高的QTL检测效力。 相似文献
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随着规模化养猪进程的加快,选育出生产性能优秀的生猪的意义日趋重要。为了促进我国养猪水平的发展,就要加强对猪遗传育种工作研究的重视程度。猪的经济性状包括繁殖性状、生长性状、胴体性状以及肉质性状,这些性状在生猪的选育改良中占据重要地位;生猪的选育方法有常规育种、转基因育种以及分子育种,随着计算机科学技术和分子生物学的发展,育种的方法也得到了发展,大量的先进的育种方法如基因组选择(GS)、标记辅助选择(MAS)、转基因和基因编辑育种等方法,有力地促进了猪经济性状的遗传改良,加快了选择进展。文章就近些年国内外猪的经济性状选择的遗传进展加以综述,旨在为我国的生猪改良提供思路和策略以及猪的选育改良提供方向。 相似文献
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文章介绍了动物数量性状育种的理论和实践,分别从数量性状遗传改良的群体层面和分子层面对选择方法进行了探讨,重点讨论了杂种优势在动物育种中的利用以及基因组选择的应用进展。 相似文献
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本研究旨在分析某杜洛克群体包括总产仔数（TNB）、产活仔数（NBA）、健仔数（NHB）、弱仔数（NWB） 4个繁殖性状的遗传参数。利用R软件对影响杜洛克猪繁殖性状的固定效应进行方差分析，并利用DMU软件计算了繁殖性状的遗传参数。结果显示：TNB、NBA、NHB和NWB的遗传力分别为0.082±0.0085、0.075±0.0082、0.066±0.0075和0.029±0.0075；此外，TNB与NBA、NHB和NWB的遗传相关变化范围是0.32～0.93。可见，在该群体中上述繁殖性状均为低遗传力性状，且遗传趋势分析表明，该杜洛克群体的母猪繁殖性状可能未经过系统的遗传改良，现有遗传进展可能与杜洛克猪生长性状的协同选择相关。本研究旨在为杜洛克猪的繁殖效率改良提供参考，为终端父本本土化贡献力量。 相似文献
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断奶后期生产性能的选择:对繁殖性能的影响在用于商业繁育体系的父系和母系选择目标中,为了确定瘦肉增重和效率的最适宜选择重点,必须了解瘦肉组织生长率和瘦肉组织饲料转化率性状组分(如:平均日增重,躯体结构和饲料转化率)与繁殖性能性状之间的遗传相关。可以根据有关性状间的遗传相关参数和它们的遗传力得到商品猪生产性能选择中繁殖性能选择反应的预期值。然而,如前所述,当遗传相关是从试验猪群亲属间或者从商品猪群较小样本的协方差得到时,则这一估测的精确性水很少是能为人接受的。在对断奶后生产性能的选择试验中,繁殖性能性状的相关… 相似文献
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利用常规的动物育种手段 ,改良胴体性状和生产性能已取得了显著的成效。采用这种方法 ,选种的准确度取决于对基因型的准确测定 ,同时必须使用适当的统计分析工具。尽管对于某些性状的选择 ,如产仔数性状 ,已取得了一定的进展 ;但对于肉质、抗病力等性状的选择 ,难度比较大 ,费用也相当高。近来 ,ＰＩＣ种猪改良公司应用基于ＤＮＡ技术的遗传改良方案 ,如遗传标记辅助选种技术 ,使得育种手段得到进一步加强。采用这些技术 ,提高了选种准确度和遗传改良效率 ,加速了遗传进展。同时 ,首次提供了对抗病性状和肉质性状进行有效选择的方法和手段。… 相似文献
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家禽数量性状基因位点的分子标记 总被引：5，自引：0，他引：5
至今,家禽的遗传改良一直沿用以数量遗传学为理论基础的常规育种方法,通过个体及其亲属的表型值,借助育种值估计方法,选择优秀遗传材料。由于经历了长期的选择,家禽的生产性能已达到相当高的水平,遗传进展递增率已下降。用现行的育种措施很难取得突破性进展的原因,在于表型选择并不总是有效的,尤其是对那些低遗传力性状。近年来,分子生物学的迅速发展,引起了育种学家的普遍关注,运用分子生物学技术改良动物生产性能,已成为当今世界动物育种科学最热门课题之一。 相似文献
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母猪的繁殖性状是猪的重要经济性状,利用分子标记辅助选择(MAS)技术可有效的对母猪的繁殖性状进行遗传改良,文章分析了PRLR、FSHβ、ESR等3个影响母猪繁殖性状的基因,阐述了这3个基因的多态性对母猪繁殖性状的影响,为选择母猪繁殖性状的分子标记以及遗传改良提供理论依据和参考。 相似文献
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The effectiveness of five selection methods for genetic improvement of net merit comprising trait 1 of low heritability (h2 = 0.1) and trait 2 of high heritability (h2 = 0.4) was examined: (i) two‐trait quantitative trait loci (QTL)‐assisted selection; (ii) partial QTL‐assisted selection based on trait 1; (iii) partial QTL‐assisted selection based on trait 2; (iv) QTL‐only selection; and (v) conventional selection index without QTL information. These selection methods were compared under 72 scenarios with different combinations of the relative economic weights, the genetic correlations between traits, the ratio of QTL variance to total genetic variance of the trait, and the ratio of genetic variances between traits. The results suggest that the detection of QTL for multiple‐trait QTL‐assisted selection is more important when the index traits are negatively correlated than when they are positively correlated. In contrast to literature reports that single‐trait marker‐assisted selection (MAS) is the most efficient for low heritability traits, this study found that the identified QTL of the low heritability trait contributed negligibly to total response in net merit. This is because multiple‐trait QTL‐assisted selection is designed to maximize total net merit rather than the genetic response of the individual index trait as in the case of single‐trait MAS. Therefore, it is not economical to identify the QTL of the low heritability traits for the improvement of total net merit. The efficient, cost‐effective selection strategy is to identify the QTL of the moderate or high heritability traits of the QTL‐assisted selection index to facilitate total economic returns. Detection of the QTL of the low h2 traits for the QTL‐assisted index selection is justified when the low h2 traits have high negative genetic correlation with the other index traits and/or when both economic weights and genetic variances of the low h2 traits are larger as compared to the other index traits of higher h2. This study deals with theoretical efficiency of QTL‐assisted selection, but the same principle applies to SNP‐based genomic selection when the proportion of the genetic variance ‘explained by the identified QTLs’ in this study is replaced by ‘explained by SNPs’. 相似文献
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Four methods of selection for net merit comprising 2 correlated traits were compared in this study: 1) EBV-only index (I?), which consists of the EBV of both traits (i.e., traditional 2-trait BLUP selection); 2) GEBV-only index (I?), which comprises the genomic EBV (GEBV) of both traits; 3) GEBV-assisted index (I?), which combines both the EBV and the GEBV of both traits; and 4) GBV-assisted index (I?), which combines both the EBV and the true genomic breeding value (GBV) of both traits. Comparisons of these indices were based on 3 evaluation criteria [selection accuracy, genetic response (ΔH), and relative efficiency] under 64 scenarios that arise from combining 2 levels of genetic correlation (r(G)), 2 ratios of genetic variances between traits, 2 ratios of the genomic variance to total genetic variances for trait 1, 4 accuracies of EBV, and 2 proportions of r(G) explained by the GBV. Both selection accuracy and genetic responses of the indices I?, I?, and I? increased as the accuracy of EBV increased, but the efficiency of the indices I? and I? relative to I? decreased as the accuracy of EBV increased. The relative efficiency of both I? and I? was generally greater when the accuracy of EBV was 0.6 than when it was 0.9, suggesting that the genomic markers are most useful to assist selection when the accuracy of EBV is low. The GBV-assisted index I? was superior to the GEBV-assisted I? in all 64 cases examined, indicating the importance of improving the accuracy of prediction of genomic breeding values. Other parameters being identical, increasing the genetic variance of a high heritability trait would increase the genetic response of the genomic indices (I?, I?, and I?). The genetic responses to I?, I?, and I(4) was greater when the genetic correlation between traits was positive (r(G) = 0.5) than when it was negative (r(G) = -0.5). The results of this study indicate that the effectiveness of the GEBV-assisted index I? is affected by heritability of and genetic correlation between traits, the ratio of genetic variances between traits, the genomic-genetic variance ratio of each index trait, the proportion of genetic correlation accounted for by the genomic markers, and the accuracy of predictions of both EBV and GBV. However, most of these affecting factors are genetic characteristics of a population that is beyond the control of the breeders. The key factor subject to manipulation is to maximize both the proportion of the genetic variance explained by GEBV and the accuracy of both GEBV and EBV. The developed procedures provide means to investigate the efficiency of various genomic indices for any given combination of the genetic factors studied. 相似文献
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Hctor Marina Antonio Reverter Beatriz Gutirrez-Gil Pamela Almeida Alexandre Rocío Pelayo Aroa Surez-Vega Cristina Esteban-Blanco Juan Jos Arranz 《Journal of animal science》2020,98(12)
Sheep milk is mainly intended to manufacture a wide variety of high-quality cheeses. The ovine cheese industry would benefit from an improvement, through genetic selection, of traits related to the milk coagulation properties (MCPs) and cheese yield-related traits, broadly denoted as “cheese-making traits.” Considering that routine measurements of these traits needed for genetic selection are expensive and time-consuming, this study aimed to evaluate the accuracy of a cheese-making phenotype imputation method based on the information from official milk control records combined with the pH of the milk. For this study, we analyzed records of milk production traits, milk composition traits, and measurements of cheese-making traits available from a total of 1,145 dairy ewes of the Spanish Assaf sheep breed. Cheese-making traits included five related to the MCPs and two cheese yield-related traits. The milk and cheese-making phenotypes were adjusted for significant effects based on a general linear model. The adjusted phenotypes were used to define a multiple-phenotype imputation procedure for the cheese-making traits based on multivariate normality and Markov chain Monte Carlo sampling. Five of the seven cheese-making traits considered in this study achieved a prediction accuracy of 0.60 computed as the correlation between the adjusted phenotypes and the imputed phenotypes. Particularly the logarithm of curd-firming time since rennet addition (logK20) (0.68), which has been previously suggested as a potential candidate trait to improve the cheese ability in this breed, and the logarithm of the ratio between the rennet clotting time and the curd firmness at 60 min (logRCT/A60) (0.65), which has been defined by other studies as an indicator trait of milk coagulation efficiency. This study represents a first step toward the possible use of the phenotype imputation of cheese-making traits to develop a practical methodology for the dairy sheep industry to impute cheese-making traits only based on the analysis of a milk sample without the need of pedigree information. This information could be also used in future planning of specific breeding programs considering the importance of the cheese-making efficiency in dairy sheep and highlights the potential of phenotype imputation to leverage sample size on expensive, hard-to-measure phenotypes. 相似文献
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(1) Pulmonary hypertension syndrome followed by ascites is a metabolic disorder in broilers that occurs more often in fast-growing birds and at cool temperatures. (2) Knowledge of the genetic relationships among ascites-related traits and performance traits like carcase traits or feed efficiency traits is required to design breeding programmes that aim to improve the degree of resistance to ascites syndrome as well as production traits. The objective of this study was to estimate these genetic correlations. (3) Three different experiments were set up to measure ascites-related traits (4202 birds), feed efficiency traits (2166 birds) and carcase traits (2036 birds). The birds in different experiments originated from the same group of parents, which enabled the estimation of genetic correlations among different traits. (4) The genetic correlation of body weight (BW) measured under normal conditions and in the carcase experiment with the ascites indicator trait of right ventricle to total ventricle ratio (RV:TV) measured under cold conditions was 0.30. The estimated genetic correlation indicated that single-trait selecting for BW leads to an increase in occurrence of the ascites syndrome but that there are realistic opportunities of multi-trait selection of birds for improved BW and resistance to ascites. (5) Weak but positive genetic relationships were found between feed efficiency and ascites-related traits suggesting that more efficient birds tend to be slightly more susceptible to ascites. (6) The relatively low genetic correlation between BW measured in the carcase or in the feed efficiency experiments and BW measured in the ascites experiment (0.49) showed considerable genotype by environment interaction. (7) These results indicate that birds with high genetic potential for growth rate under normal temperature conditions have lower growth rate under cold-stress conditions due to ascites. 相似文献
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Records on 514 bulls from the sire population born from 1978 to 2004, and on 22,099 of their field progeny born from 1997 to 2003 with available pedigree information (total number = 124,458) were used to estimate genetic parameters for feed intake and energy efficiency traits of bulls and their relationships with carcass traits of field progeny. Feed intake and energetic efficiency traits were daily feed intake, TDN intake, feed conversion ratio (FCR), TDN conversion ratio (TDNCR), residual feed intake (RFI), partial efficiency of growth, relative growth rate, and Kleiber ratio. Progeny carcass traits were carcass weight (CWT), yield estimate, ribeye area, rib thickness, subcutaneous fat thickness (SFT), marbling score (MSR), meat color standard (MCS), fat color standard (FCS), and meat quality grade. All measures of feed intake and energetic efficiency were moderately heritable (ranged from 0.24 to 0.49), except for partial efficiency of growth and relative growth rate, which were high (0.58) and low (0.14), respectively. The phenotypic and genetic correlations between FCR and TDNCR were >or=0.93. Selection for Kleiber ratio will improve all of the energetic efficiency traits with no effect on feed intake measures (daily feed intake and TDN intake). The genetic correlations of FCR, TDNCR, and RFI of bulls with most of the carcass traits of their field progeny were favorable (ranged from -0.24 to -0.72), except with fat color standard (no correlation), MCS, and SFT. Positive (unfavorable) genetic correlations of MCS with FCR, TDNCR, and RFI (0.79, 0.70, and 0.51, respectively) were found. The SFT was negatively genetically correlated with FCR and TDNCR (-0.32 and -0.20, respectively); however, the genetic correlation between RFI and SFT was not significantly different from zero (r(g) = -0.08 +/- 0.12). Favorable correlated responses in CWT, yield estimate, ribeye area, rib thickness, MSR, and meat quality grade would be predicted for selection against any measure of energetic efficiency. The correlated responses in CWT and MSR of progeny were greater for selection against RFI than for selection against any other energetic efficiency trait. Results of this study indicate that RFI should be preferred over other measures of energetic efficiency to include in selection programs. 相似文献
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A bio-economic model was developed to evaluate utilization of beef bulls in a variety of production systems. The model can simulate life-cycle production of both beef and dairy cow herds with or without an integrated feedlot system. The Markov chain approach is used to simulate herd dynamics. The herd is described in terms of animal states and possible transitions among them. Equilibrium herd structures of the integrated production systems are calculated in their stationary states. The economic efficiency of each system is a function of biological traits of animals and of management and economic parameters. The model allows estimation of marginal economic values for 16 traits separately in each system. The economic weight for each trait or direct and maternal trait component in each selection group and breed of interest is then calculated as the weighted sum of the economic values for the trait in all production systems in which the selection group has an impact. Weighting factors for each system are computed as the product of the number of discounted expressions for direct and maternal trait components transmitted in that system by the selection group and the proportion of total cows belonging to each system. 相似文献
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An evaluation of alternative selection indexes for a non‐linear profit trait approaching its economic optimum 
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下载免费PDF全文 D. Martin‐Collado T.J. Byrne B. Visser P.R. Amer 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2016,133(6):476-484
This study used simulation to evaluate the performance of alternative selection index configurations in the context of a breeding programme where a trait with a non‐linear economic value is approaching an economic optimum. The simulation used a simple population structure that approximately mimics selection in dual purpose sheep flocks in New Zealand (NZ). In the NZ dual purpose sheep population, number of lambs born is a genetic trait that is approaching an economic optimum, while genetically correlated growth traits have linear economic values and are not approaching any optimum. The predominant view among theoretical livestock geneticists is that the optimal approach to select for nonlinear profit traits is to use a linear selection index and to update it regularly. However, there are some nonlinear index approaches that have not been evaluated. This study assessed the efficiency of the following four alternative selection index approaches in terms of genetic progress relative to each other: (i) a linear index, (ii) a linear index updated regularly, (iii) a nonlinear (quadratic) index, and (iv) a NLF index (nonlinear index below the optimum and then flat). The NLF approach does not reward or penalize animals for additional genetic merit beyond the trait optimum. It was found to be at least comparable in efficiency to the approach of regularly updating the linear index with short (15 year) and long (30 year) time frames. The relative efficiency of this approach was slightly reduced when the current average value of the nonlinear trait was close to the optimum. Finally, practical issues of industry application of indexes are considered and some potential practical benefits of efficient deployment of a NLF index in highly heterogeneous industries (breeds, flocks and production environments) such as in the NZ dual purpose sheep population are discussed. 相似文献
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Performance of the "quasi-REML" method for estimating correlations between a continuous trait and a categorical trait, and between two categorical traits, was studied with Monte Carlo simulations. Three continuous, correlated traits were simulated for identical populations and three scenarios with either no selection, selection for one moderately heritable trait (Trait 1, h2 = .25), and selection for the same trait plus confounding between sires and management groups. The "true" environmental correlations between Traits 2 (h2 = .10) and 3 (h2 = .05) were always of the same absolute size (.20), but further data scenarios were generated by setting the sign of environmental correlation to either positive or negative. Observations for Traits 2 and 3 were then reassigned to binomial categories to simulate health or reproductive traits with incidences of 15 and 5%, respectively. Genetic correlations (r(g12), r(g13), and r(g23) and environmental correlations (r(e12), r(e13), and r(e23)) were estimated for the underlying continuous scale (REML) and the visible categorical scales ("quasi-REML") with linear multiple-trait sire and animal models. Contrary to theory, practically all "quasi-REML" genetic correlations were underestimated to some extent with the sire and animal models. Selection inflated this negative bias for sire model estimates, and the sign of r(e23) noticeably affected r(g23) estimates for the animal model, with greater bias and SD for estimates when the "true" r(e23) was positive. Transformed "quasi-REML" environmental correlations between a continuous and a categorical trait were estimated with good efficiency and little bias, and corresponding correlations between two categorical traits were systematically overestimated. Confounding between sires and contemporary groups negatively affected all correlation estimates on the underlying and the visible scales, especially for sire model "quasi-REML" estimates of genetic correlation. Selection, data structure, and the (co)variance structure influences how well correlations involving categorical traits are estimated with "quasi-REML" methods. 相似文献
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性别比例和性状遗传力对闭锁群体BLUP选择效果的影响 总被引：2，自引：0，他引：2
采用MonteCarlo方法模拟研究了性别比例和性状遗传力对闭锁群体动物模型BLUP选择效果的影响 ,选育过程中世代不重叠 ,共进行了 1 5个世代的选择。结果表明性别比例对群体育种值和近交系数的变化都有明显的影响。在育种值达到最大值以前 ,群体平均育种值提高的速度随着公畜比例的增加而有所减慢 ,但会使育种值达到最大值的时间后移 ,在育种值达到最大值后 ,其下降的速度则随着公畜比例的降低而加快。随着公畜比例的增加 ,群体近交系数的上升速度会明显变慢。高遗传力性状的选择效果要优于低遗传力性状 相似文献
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H. Chapuis C. Pincent J.J. Colleau 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2016,133(1):3-12
Poultry breeding schemes permanently face the need to control the evolution of coancestry and some critical traits, while selecting for a main breeding objective. The main aims of this article are first to present an efficient selection algorithm adapted to this situation and then to measure how the severity of constraints impacted on the degree of loss for the main trait, compared to BLUP selection on the main trait, without any constraint. Broiler dam and sire line schemes were mimicked by simulation over 10 generations and selection was carried out on the main trait under constraints for coancestry and for another trait, antagonistic with the main trait. The selection algorithm was a special simulated annealing (adaptative simulated annealing (ASA)). It was found to be rapid and able to meet constraints very accurately. A constraint on the second trait was found to induce an impact similar to or even greater than the impact of the constraint on coancestry. The family structure of selected poultry populations made it easy to control the evolution of coancestry at a reasonable cost but was not as useful for reducing the cost of controlling evolution of the antagonistic traits. Multiple constraints impacted almost additively on the genetic gain for the main trait. Adding constraints for several traits would therefore be justified in real life breeding schemes, possibly after evaluating their impact through simulated annealing. 相似文献