Bahreini Behzadi M R, Shahroudi F E, Van Vleck L D
Department of Animal Sciences, Faculty of Agriculture, Yasouj University, Iran.
J Anim Breed Genet. 2007 Oct;124(5):296-301. doi: 10.1111/j.1439-0388.2007.00672.x.
Birth weight (BW), weaning weight (WW), 6-month weight (W6), 9-month weight (W9) and yearling weight (YW) of Kermani lambs were used to estimate genetic parameters. The data were collected from Shahrbabak Sheep Breeding Research Station in Iran during the period of 1993-1998. The fixed effects in the model were lambing year, sex, type of birth and age of dam. Number of days between birth date and the date of obtaining measurement of each record was used as a covariate. Estimates of (co)variance components and genetic parameters were obtained by restricted maximum likelihood, using single and two-trait animal models. Based on the most appropriate fitted model, direct and maternal heritabilities of BW, WW, W6, W9 and YW were estimated to be 0.10 +/- 0.06 and 0.27 +/- 0.04, 0.22 +/- 0.09 and 0.19 +/- 0.05, 0.09 +/- 0.06 and 0.25 +/- 0.04, 0.13 +/- 0.08 and 0.18 +/- 0.05, and 0.14 +/- 0.08 and 0.14 +/- 0.06 respectively. Direct and maternal genetic correlations between the lamb weights varied between 0.66 and 0.99, and 0.11 and 0.99. The results showed that the maternal influence on lamb weights decreased with age at measurement. Ignoring maternal effects in the model caused overestimation of direct heritability. Maternal effects are significant sources of variation for growth traits and ignoring maternal effects in the model would cause inaccurate genetic evaluation of lambs.
克尔曼尼羔羊的出生体重（BW）、断奶体重（WW）、6月龄体重（W6）、9月龄体重（W9）和周岁体重（YW）被用于估计遗传参数。数据收集于1993年至1998年期间伊朗的沙尔巴巴克绵羊育种研究站。模型中的固定效应包括产羔年份、性别、出生类型和母羊年龄。每个记录的出生日期与获取测量日期之间的天数用作协变量。使用单性状和双性状动物模型，通过限制最大似然法获得（协）方差分量和遗传参数的估计值。基于最合适的拟合模型，BW、WW、W6、W9和YW的直接遗传力和母体遗传力估计值分别为0.10±0.06和0.27±0.04、0.22±0.09和0.19±0.05、0.09±0.06和0.25±0.04、0.13±0.08和0.18±0.05，以及0.14±0.08和0.14±0.06。羔羊体重之间的直接遗传相关性和母体遗传相关性在0.66至0.99以及0.11至0.99之间变化。结果表明，母体对羔羊体重的影响随着测量时的年龄增加而降低。在模型中忽略母体效应会导致直接遗传力的高估。母体效应是生长性状变异的重要来源，在模型中忽略母体效应会导致对羔羊的遗传评估不准确。
