基于 X 射线计算机断层扫描技术的羔羊胴体质量特性与现行英国山地绵羊选育目标之间的关系。

1Sustainable Livestock Systems Group, SAC, West Mains Road, Edinburgh EH9 3JG, UK.

Animal. 2008 Jan;2(1):36-43. doi: 10.1017/S1751731107001061.

Genetic parameters were estimated between current UK hill sheep breeding goals and lamb carcass composition and muscularity traits derived using X-ray computed tomography (CT). To produce these estimates, a total of 648 lambs from two hill farms were CT scanned at weaning (ca 120 days of age), over 3 years, and total weights of carcass muscle (MUSC), fat (CFAT) and bone (BONE) and internal fat (IFAT) were predicted. Previously derived muscularity indices were also calculated for the hind leg (HLMI) and lumbar (LRMI) regions, to assess muscle shape. Data for current breeding goals (lamb performance and maternal traits) were also included from a total of 10 297 lamb records and 12 704 ewe records. Heritabilities were estimated for each trait and genetic and phenotypic correlations were calculated between each CT trait and other lamb or ewe traits. Moderate to high positive genetic correlations were found between CT-predicted tissue weights and breeding goals, which were also weights (lamb weaning weight, carcass weight, mature ewe weight, average weight of lambs reared by the ewe). CFAT was positively genetically correlated with ultrasound backfat depth at weaning (UFD) and subjective fatness grade at slaughter (MLCF), suggesting that carcass fat could be decreased using selection on any of these predictors. Ultrasound muscle depth at weaning (UMD) and subjective conformation score at slaughter (MLCC) had high genetic correlations with the muscularity indices (HLMI and LRMI), but correlations with MUSC were not significantly different from zero. This implies that selection to improve MLCC is likely to be increasing the 'roundness' of muscle shape in the high-priced carcass region, but having little impact on total lean meat yield. Correlations of CT traits with the other ewe traits (number of lambs weaned, number of lambs lost, longevity, fleece weight) were generally small or not significantly different from zero. The genetic parameters generated in this study can now be used in selection index calculations to assess the benefits of including lamb CT traits in future selection programmes for hill sheep.

遗传参数是通过 X 射线计算机断层扫描（CT）对当前英国山地绵羊育种目标与羔羊胴体组成和肌肉特性进行预测而估算出来的。为了得出这些估计值，我们对来自两个山地农场的总共 648 只羔羊在断奶时（约 120 天大）进行了 CT 扫描，这些羔羊在 3 年的时间内接受了扫描，并预测了胴体肌肉（MUSC）、脂肪（CFAT）、骨骼（BONE）和内部脂肪（IFAT）的总重量。还为后腿（HLMI）和腰椎（LRMI）区域计算了之前推导出的肌肉发达指数，以评估肌肉形状。还包括了总共 10297 只羔羊记录和 12704 只母羊记录中的当前育种目标（羔羊性能和母性特征）的数据。对每个性状进行了遗传力估计，并计算了每个 CT 性状与其他羔羊或母羊性状之间的遗传和表型相关性。发现 CT 预测的组织重量与育种目标之间存在中度至高度的正遗传相关性，这些目标也是重量（羔羊断奶体重、胴体重、成年母羊体重、母羊饲养的羔羊平均体重）。CFAT 与断奶时的超声背膘厚（UFD）和屠宰时的主观脂肪等级（MLCF）呈正遗传相关，这表明可以通过对这些预测指标中的任何一个进行选择来减少胴体脂肪。断奶时的超声肌肉深度（UMD）和屠宰时的主观体型评分（MLCC）与肌肉发达指数（HLMI 和 LRMI）之间具有较高的遗传相关性，但与 MUSC 的相关性并不显著为零。这意味着选择改善 MLCC 可能会增加高价位胴体部位肌肉形状的“圆润度”，但对总瘦肉产量的影响不大。CT 性状与其他母羊性状（断奶羔羊数、丢失羔羊数、寿命、羊毛重量）之间的相关性通常较小或不显著为零。本研究中生成的遗传参数现在可用于选择指数计算，以评估在未来山地绵羊的选择计划中包含羔羊 CT 性状的收益。