Cooperative Research Centre for Sheep Industry Innovation, Armidale, NSW 2350, Australia.
J Anim Sci. 2013 Jan;91(1):78-89. doi: 10.2527/jas.2012-5482. Epub 2012 Oct 9.
Lambs with the myostatin (MSTN) g+6723G>A mutation have a greater muscle mass, which is believed to be associated with reduced myostatin protein abundance. This experiment was designed to determine if differences in allelic frequency of the MSTN g+6723G>A mutation affected abundance of myostatin protein from birth to 24 wk of age. A Poll Dorset cross White Suffolk ram (MSTN A/G) was mated to 35 White Suffolk cross Border Leicester cross Merino ewes (MSTN A/G, n=21, and MSTN G/G, n=14). The progeny of these matings delivered 44 lambs with MSTN A/A (n=9), MSTN A/G (n=21), and MSTN G/G (n=14) genotypes. At approximately 1, 4, and 12 wk of age, a biopsy sample was collected and a blood sample was taken to measure the abundance of myostatin protein in muscle and plasma. At approximately 24 wk of age, the wether lambs were slaughtered to determine carcass characteristics and muscle samples were taken from the bicep femoris. The abundance of mature myostatin protein in muscle from 1 wk old lambs was less (P=0.05) in MSTN A/A and MSTN A/G compared with MSTN G/G lambs. However, at 4 and 24 wk the MSTN A/A lambs had a greater (P=0.04) abundance of myostatin protein compared with the MSTN A/G and MSTN G/G lambs. The abundance of mature myostatin did not differ between genotypes in plasma but the myostatin protein did increase as the lambs aged. At slaughter the MSTN A/A wether lambs had greater dressing percentages (P=0.04), shortloin (P=0.01), topside (P<0.001), and round (P=0.01) weights but did not differ in final BW or HCW (P>0.05). The MSTN A/A lambs had more muscle fibers (P=0.02) in the cross-section of LM between the 12th and 13th rib. The MSTN A/A lambs also had greater lean (P=0.002), less fat (P=0.009), and reduced organ (heart, liver, spleen, and kidneys) mass as determined by computed tomography scanning than MSTN G/G lambs. The results of this study demonstrated that lambs homozygous for the MSTN g+6723G>A mutation have changes in carcass characteristics (dressing and total lean), organ weights, and muscle fiber number. This may be due to reduced myostatin protein early in utero, but after 4 wk of age there was no difference in the abundance of mature myostatin protein in muscle or plasma among MSTN A/A, MSTN A/G, and MSTN G/G genotypes.
羔羊携带肌肉生长抑制素（MSTN）g+6723G>A 突变，肌肉量更大，据信与肌肉生长抑制素蛋白丰度降低有关。本实验旨在确定 MSTN g+6723G>A 突变的等位基因频率差异是否会影响羔羊出生至 24 周龄时肌肉生长抑制素蛋白的丰度。一头 Poll Dorset 杂交白萨福克公羊（MSTN A/G）与 35 头白萨福克杂交边区莱斯特杂交美利奴母羊（MSTN A/G，n=21，和 MSTN G/G，n=14）交配。这些交配的后代产下了 44 只羔羊，基因型分别为 MSTN A/A（n=9）、MSTN A/G（n=21）和 MSTN G/G（n=14）。大约在 1、4 和 12 周龄时，采集了活检样本并采集了血液样本，以测量肌肉和血浆中肌肉生长抑制素蛋白的丰度。大约在 24 周龄时，淘汰去势公羊以确定胴体特征，并从二头肌股骨中采集肌肉样本。1 周龄羔羊肌肉中成熟肌肉生长抑制素蛋白的丰度（P=0.05）在 MSTN A/A 和 MSTN A/G 组中低于 MSTN G/G 组。然而，在 4 周和 24 周时，MSTN A/A 羔羊的肌肉生长抑制素蛋白丰度（P=0.04）高于 MSTN A/G 和 MSTN G/G 羔羊。在血浆中，不同基因型之间的成熟肌肉生长抑制素的丰度没有差异，但随着羔羊年龄的增长，肌肉生长抑制素蛋白确实增加了。在屠宰时，MSTN A/A 去势公羊具有更高的着装率（P=0.04）、短腰肉（P=0.01）、顶部（P<0.001）和圆形（P=0.01）重量，但最终体重或活重（P>0.05）没有差异。MSTN A/A 羔羊在第 12 和第 13 肋之间的 LM 横截面上具有更多的肌纤维（P=0.02）。MSTN A/A 羔羊的瘦肉（P=0.002）、脂肪（P=0.009）和器官（心脏、肝脏、脾脏和肾脏）质量减少，这是通过计算机断层扫描确定的，与 MSTN G/G 羔羊相比。本研究结果表明，携带 MSTN g+6723G>A 突变的羔羊在胴体特征（着装和总瘦肉）、器官重量和肌纤维数量方面发生了变化。这可能是由于胎儿早期肌肉生长抑制素蛋白减少，但在 4 周龄后，MSTN A/A、MSTN A/G 和 MSTN G/G 基因型之间肌肉中成熟肌肉生长抑制素蛋白的丰度没有差异。
