R法遗传参数估值置信区间的计算方法和重复估计次数的研究

探讨R法遗传参数估值置信区间的计算方法和重复估计次数(NORE)对参数估值的影响，利用4种模型通过模拟产生数据集。基础群中公、母畜数分别为200和2000头，BLUP育种值选择5个世代。利用多变量乘法迭代(MMI)法，结合先决条件的共扼梯度(PCG)法求解混合模型方程组估计方差组分。用经典方法、Box-Cox变换后的经典方法和自助法计算参数估值的均数、标准误和置信区间。结果表明，重复估计次数较多时，3种方法均可；重复估计次数较少时，建议使用自助法。简单模型下需要较少的重复估计，但对于复杂模型则需要较多的重复估计。随模型中随机效应数的增加，直接遗传力高估。随着PCG和MMI轮次的增大，参数估值表现出低估的趋势。

Study on the Calculation Methods of Confidence Intervals of Genetic Parameter Estimates by Method R and Number of Repeating Estimations

The objective of the study was to probe the calculation methods of confidence intervals of genetic parameter estimates by Method R and influences of number of repeating estimations (NORE).Four models were used to generate the datasets by simulation.The datasets originated from 200 sires and 2 000 dams and simulation progressed by BLUP(Best Linear Unbiased Prediction) selection for five overlapping generations.Variance components were estimated by using multivariate multiplicative iteration (MMI),combined with preconditioned conjugate gradient (PCG) to solve the mixed model equations.Parameter estimates and their standard errors and confidence intervals were computed by classical method,classical method after Box-Cox transformation and bootstrapping.The results showed that when NORE was larger,all three methods were feasible,but when NORE was fewer,bootstrapping was recommended.Fewer NORE was feasible under simple models,but more NORE was needed for complex models.Direct heritabilities were overestimated with the increase of number of random effects,but underestimation was found for many parameters with the increase of iteration numbers of PCG and MMI.