Commonly used aquatic feed naturally contains low-level or no hydroxyproline (Hyp). This study was conducted to evaluate the effects of dietary Hyp inclusion on growth performance, body composition, amino acid profiles, blood biochemistry, and the expression of target of rapamycin (TOR) pathway-related genes in juvenile Nibea diacanthus. Fish with similar size (initial body weight, 133.00 ± 2.14 g) were fed six isonitrogenous and isolipidic practical diets supplemented with graded levels of Hyp (0, 5, 10, 15, 20, and 25 g kg⁻¹ of dry matter) for 8 weeks. The results indicated that growth performance and feed utilization were improved with increased levels of dietary Hyp (P < 0.05), and the optimum amount of dietary Hyp estimated from SGR as 16.6 g kg⁻¹. The crude protein of whole body and swim bladder and the amino acid composition of muscle and swim bladder were significantly (P < 0.05) affected by the addition of dietary Hyp, which reflects the important role of feed composition in animal body composition. In addition, the expression levels of mammalian target of rapamycin (TOR) and ribosomal protein S6 kinase1 (S6K1) genes in the liver, muscle, and swim bladder increased with increasing Hyp content of diets, while the mRNA expression level of eukaryotic translation initiation factor 4E-binding protein (4E-BP) gene in these tissues decreased. These results indicated that Hyp improved fish growth and the ability to synthesize proteins, most likely through the TOR pathway. It is suggested that dietary Hyp supplementation is particularly necessary for application in aquatic feed.

常用的水产饲料天然含有少量或不含羟脯氨酸（Hyp）。进行这项研究以评估饮食中加入Hyp对少年Ni虫的生长性能，身体组成，氨基酸谱，血液生化以及雷帕霉素（TOR）途径相关基因的靶标表达的影响。饲喂六种大小相似（初始体重为133.00±2.14 g）的鱼，补充六种等氮和等脂的实际饮食，并补充分级的Hyp（0、5、10、15、20和25 g kg ^-1干物质）。 8个星期。结果表明，随着日粮Hyp含量的增加，生长性能和饲料利用率得到改善（P <0.05），根据SGR估算的最佳日粮Hyp量为16.6 g kg^-1。全身和膀胱的粗蛋白和肌肉和膀胱的氨基酸组成均显着（P<0.05）受饲料中Hyp含量的影响，这反映了饲料成分在动物体成分中的重要作用。此外，随着日粮中Hyp含量的增加，雷帕霉素（TOR）和核糖体蛋白S6激酶1（S6K1）基因在哺乳动物靶标中的表达水平随日粮Hyp含量的增加而增加，而真核翻译起始因子的mRNA表达水平则升高这些组织中的4E结合蛋白（4E-BP）基因减少。这些结果表明，Hyp最有可能通过TOR途径改善了鱼类的生长和蛋白质合成的能力。建议将膳食Hyp补充剂用于水产饲料特别必要。