PDF(Pubmed)
Abstract：
This study provides estimates on genetic parameters, inbreeding depression and purging for meat performance measures from 25 German sheep breeds. All German meat, merino sheep breeds and breeds of other breeding directions with a sufficient number of pedigree and performance data were included in this study. Phenotypic traits retrieved from the national database OviCap were evaluated: daily weight gain, meatiness score and ultrasound measurements for muscle and fat thickness. We employed animal models to estimate heritability, variance and covariance components for these meat performance traits as well as inbreeding depression and purging. The heritabilities, on average, reached estimates of 0.55, 0.34, 0.53 and 0.61 for daily weight gain, meatiness score and ultrasound measurements for muscle and fat thickness, respectively. We estimated the linear regression slopes for the individual rate of inbreeding, new and ancestral inbreeding, as well as the inbreeding coefficient and its interaction with the inbreeding coefficient of Ballou, employing animal models with non-genetic effects and the additive genetic effect of the animal. Across all breeds, inbreeding was only significant for daily weight gain, whereas for all other traits, estimates were not significant. Within sheep breeds, we found significant inbreeding depression for daily weight gain in German Mutton Merino and German Blackheaded Mutton as well as for the meatiness score in German Whiteheaded Mutton. Significant effects for purging, based on ancestral inbreeding and the interaction effect of the classical inbreeding coefficient with the inbreeding coefficient of Ballou, were not obvious either across or within any sheep breed. A 1% increase in inbreeding significantly decreased the phenotypic trait median of daily weight gain across all sheep breeds by 0.50% and 0.70% of phenotypic and genetic standard deviation, respectively. Purging effects due to ancestral inbreeding were not significant in any breed or across breeds. The results of this study may indicate that inbreeding depression may be more harmful in traits under stronger selection than in traits that exert low selection pressure. The results of this study demonstrate the different effects that result in meat performance traits due to inbreeding. With increasing rates of inbreeding and critical effective population sizes, selection intensity for breeding objectives has to be critically reviewed for each sheep breed. Inbreeding depression and purging should be evaluated in order to prevent a decrease in trait means due to inbreeding and to determine whether detrimental alleles are eliminated.
摘要：
这项研究提供了对遗传参数的估计，来自25个德国绵羊品种的近交抑制和肉类表现指标的清除。所有德国肉，本研究包括了具有足够数量的谱系和性能数据的美国美国美国羊品种和其他育种方向的品种。从国家数据库OviCap检索的表型性状进行了评估：每日体重增加，肉质评分和肌肉和脂肪厚度的超声测量。我们用动物模型来估计遗传力，这些肉类表现性状的方差和协方差成分以及近交抑制和净化。遗传力，平均而言,每日体重增加达到0.55、0.34、0.53和0.61的估计值，肉质评分和肌肉和脂肪厚度的超声测量，分别。我们估计了个体近亲繁殖率的线性回归斜率，新的和祖先的近亲繁殖，以及近交系数及其与Ballou近交系数的相互作用，采用具有非遗传效应和动物的加性遗传效应的动物模型。在所有品种中，近亲繁殖仅对每日体重增加有意义，而对于所有其他特征，估计并不重要。在绵羊品种中，我们发现，德国羊肉梅里诺和德国黑头羊肉的每日体重增加以及德国白头羊肉的肉质评分明显减少。清除的重大影响，基于祖先近亲繁殖和经典近亲繁殖系数与Ballou近亲繁殖系数的交互效应，在任何绵羊品种中或在任何绵羊品种中都不明显。近交增加1％，使所有绵羊品种的表型性状中位数日增重显着降低了0.50％和0.70％的表型和遗传标准偏差，分别。由于祖先近亲繁殖而产生的净化效应在任何品种或跨品种中都不显著。这项研究的结果可能表明，在较强的选择下，近交抑郁对性状的危害可能比施加较低选择压力的性状更大。这项研究的结果表明，由于近交，导致肉性能性状的不同影响。随着近亲繁殖率和关键有效种群规模的增加，必须严格审查每个绵羊品种的育种目标选择强度。应评估近交抑制和清除，以防止由于近交导致的性状降低，并确定是否消除了有害等位基因。
