Johnson P L, Dodds K G, Bain W E, Greer G J, McLean N J, McLaren R J, Galloway S M, van Stijn T C, McEwan J C
AgResearch Invermay, Puddle Alley, Private Bag 50034, Mosgiel, New Zealand.
J Anim Sci. 2009 Jun;87(6):1856-64. doi: 10.2527/jas.2008-1508. Epub 2009 Feb 27.
This work investigated effects of carrying 0, 1, or 2 copies of the A allele resulting from the g+6723G-A transition in growth differentiation factor gene (GDF8) in New Zealand Texel-cross sheep at different lamb ages and carcass weights. Two Texel-cross sires carrying 1 copy of the A allele were mated to approximately 200 ewes carrying 0, 1, or 2 copies of the A allele. A total of 187 progeny were generated and genotyped to determine whether they were carrying 0, 1, or 2 copies of the A allele. The progeny were assigned to 1 of 4 slaughter groups balanced for the 3 genotypes, sex, and sire. The 4 groups were slaughtered commercially when their average BW (across all progeny in the slaughter group) reached 33, 40, 43, and 48 kg, respectively. Measurements of BW, and carcass dimensions and yield were made on all animals using Viascan (a commercial 2-dimensional imaging system that estimates lean content of the carcass as a percentage of total carcass weight). Additional measurements were made on the fourth slaughter group, which was computed tomography scanned at each slaughter time point to obtain 4 serial measures of lean and fat as estimated from the computed tomography images. The A allele did not have an effect on any BW traits. The A allele was associated with increased muscle and decreased fat across the variety of measures of muscling and fat, explaining between 0.2 and 1.1 of a residual SD unit. Estimates for an additive effect were significant and were positive for muscle and negative for fat traits. No dominance effect estimates (positive or negative) were significant. There was no significant interaction between A allele number and carcass weight or slaughter group for any trait. This is the first systematic study of the effect of the A allele copy number over a range of carcass weights (13 to 20 kg) and ages and results suggest the size of the effect across these endpoints is proportionately the same. Testing for the A allele therefore offers breeders the potential to improve rates of genetic gain for lean-meat yield across most production systems.
本研究调查了生长分化因子基因（GDF8）中g+6723G-A转换产生的A等位基因的0、1或2个拷贝对不同羔羊年龄和胴体重量的新西兰特克塞尔杂交绵羊的影响。将携带1个A等位基因拷贝的两只特克塞尔杂交公羊与大约200只携带0、1或2个A等位基因拷贝的母羊交配。共产生了187只后代，并对其进行基因分型，以确定它们携带的是0、1还是2个A等位基因拷贝。这些后代被分配到4个屠宰组中的1个，各组在基因型、性别和父本方面保持平衡。当4个组的平均体重（屠宰组中所有后代的平均体重）分别达到33、40、43和48千克时，对其进行商业屠宰。使用Viascan（一种商业二维成像系统，可将胴体瘦肉含量估算为胴体总重量的百分比）对所有动物进行体重、胴体尺寸和产量测量。对第四个屠宰组进行了额外测量，在每个屠宰时间点对其进行计算机断层扫描，以从计算机断层扫描图像中获得瘦肉和脂肪的4个连续测量值。A等位基因对任何体重性状均无影响。在各种肌肉和脂肪测量指标中，A等位基因与肌肉增加和脂肪减少相关，可解释0.2至1.1个残差标准差单位。加性效应估计值显著，对肌肉为正，对脂肪性状为负。没有显性效应估计值（正或负）显著。对于任何性状，A等位基因数量与胴体重量或屠宰组之间均无显著交互作用。这是首次对一系列胴体重量（13至20千克）和年龄范围内A等位基因拷贝数的影响进行系统研究，结果表明在这些终点上效应的大小成比例相同。因此，检测A等位基因可为育种者提供在大多数生产系统中提高瘦肉产量遗传增益率的潜力。
