The development of skeletal muscle is a crucial factor in determining the meat yield and economic benefits of broiler production. Recent research has shown that mulberry leaves and their extracts can be used to significantly improve the growth performance of livestock and poultry. The present study aims to elucidate the mechanisms involved in the regulation of skeletal muscle development in broiler offspring by dietary mulberry-leaf flavonoids (MLF) supplementation from the perspective of maternal effect theory. A total of 270 Qiling broiler breeder hens were randomly assigned to 3 treatments with different doses of MLF (0, 30, 60 mg/kg) for 8 weeks before collecting their fertilized eggs. The chicken offspring at 13 and 19 d of embryonic stage, and from 1 to 28 d old after hatching were included in this study. The results showed that maternal supplementation increased the breast muscle weight and body weight of the offspring at the embryo and chick stages ( < 0.05). This was followed by increased cross-sectional area of pectoral muscle fibres at 14 d ( < 0.05). Further determination revealed a tendency towards increased serum levels of insulin-like growth factor 1 (IGF-1) ( = 0.092) and muscle fibre count ( = 0.167) at 1 d post-hatching following maternal MLF treatment, while serum uric acid (UA) was decreased at 14 d after hatching ( < 0.05). Moreover, maternal MLF supplementation significantly up-regulated the mRNA expression of the myogenic regulatory factor in skeletal muscle at the both embryonic and growth stages ( < 0.05). The relative abundance of the downstream protein of BMPR2, Smad1 and p-Smad1/5/9 in the TGFβ signalling pathway was significantly increased by maternal MLF treatment. Meanwhile, the increased expression of the target protein p-mTOR in the breast muscle of the offspring chicks is in accordance with the improved growth rate of the breast and the body. In conclusion, maternal MLF supplementation can promote muscle protein metabolism and muscle fibre development of chick embryos through upregulation of expression and BMP/p-Smad1/5/9 axis, thereby improving growth performance of slow growing broiler.

中文翻译：

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母体补充桑叶黄酮可改善鸡后代骨骼肌的发育


骨骼肌的发育是决定肉鸡生产产肉量和经济效益的关键因素。最近的研究表明，桑叶及其提取物可显着改善畜禽的生长性能。本研究旨在从母体效应理论的角度阐明日粮中补充桑叶黄酮（MLF）调节肉鸡后代骨骼肌发育的机制。将270只麒麟肉种鸡随机分为3个处理组，分别给予不同剂量MLF（0、30、60 mg/kg），为期8周，然后收集受精卵。本研究包括胚胎期13天和19天以及孵化后1至28天的鸡后代。结果表明，母体补充增加了胚胎和雏鸡阶段子代的胸肌重量和体重（<0.05）。随后第 14 天胸肌纤维横截面积增加（<0.05）。进一步测定显示，母体 MLF 处理后孵化后 1 d，血清胰岛素样生长因子 1 (IGF-1) (= 0.092) 和肌纤维计数 (= 0.167) 的血清水平有增加的趋势，而血清尿酸 (UA) ）在孵化后 14 d 时下降（ < 0.05）。此外，母体补充 MLF 显着上调胚胎和生长阶段骨骼肌中生肌调节因子的 mRNA 表达（<0.05）。母体MLF治疗显着增加了TGFβ信号通路中BMPR2、Smad1和p-Smad1/5/9下游蛋白的相对丰度。 同时，子代雏鸡胸肌中靶蛋白p-mTOR表达增加与乳房和身体生长速度的提高相一致。总之，母体补充MLF可以通过上调表达和BMP/p-Smad1/5/9轴来促进鸡胚肌肉蛋白代谢和肌纤维发育，从而改善生长缓慢的肉鸡的生长性能。