饲料中添加蛋氨酸寡肽对大黄鱼(Larimichthys crocea)生长、饲料利用和蛋白质代谢反应的影响

为研究饲料中添加蛋氨酸寡肽(OMet)对大黄鱼(Larimichthys crocea)幼鱼生长、饲料利用和蛋白质代谢反应的影响,并与在饲料中添加等量的晶体蛋氨酸(CMet)的效果相比,实验以初始体重为(26.0±1.6)g的大黄鱼幼鱼为研究对象,以鱼粉和豆粕为主要蛋白源,设计1个低鱼粉(31.8％)对照饲料(LF).在LF的基础上分别添加0.35％、0.65％和0.95％的晶体蛋氨酸或蛋氨酸寡肽,配制其他6组饲料,并分别命名为CMet 0.35、CMet 0.65、CMet 0.95、OMet 0.35、OMet 0.65和OMet 0.95,养殖周期为8周.结果显示,与LF组相比,OMet组和CMet组大黄鱼的增重率均显著升高,并随着蛋氨酸水平的增加而显著提高(P＜0.05),其中,OMet 0.95组的增重率最高.与CMet组相比,OMet组大黄鱼的增重率和蛋白质效率均显著提高(P＜0.05).不同饲料处理对大黄鱼存活率、饲料系数、体组成(粗蛋白、粗脂肪、灰分和水分)、脏体比和肥满度没有显著影响(P＞0.05).OMet组大黄鱼的肝体比较CMet组显著降低(P＜0.05).饲料中添加晶体或蛋氨酸寡肽显著影响了大黄鱼幼鱼的肝脏谷丙转氨酶和谷草转氨酶活力,OMet组大黄鱼肝脏中这两种酶的活力均显著高于CMet组的(P＜0.05),蛋氨酸添加水平对大黄鱼肝脏谷草转氨酶活力也有显著影响(P＜0.05).但各饲料处理组之间血清中的血氨浓度和尿素氮含量没有显著差异(P＞0.05).综上所述,等量添加蛋氨酸寡肽比晶体蛋氨酸更能促进大黄鱼幼鱼的生长及其对饲料的利用.

Effects of Dietary Oligo-Methionine on the Growth Performance, Feed Utilization and Protein Metabolism Responses of Juvenile Large Yellow Croaker (Larimichthys crocea)

Enzyme-catalyzed synthesis of oligo-methionine (OMet) has been available, however, little is known on the application of OMet in aquatic feed. In this study, an 8 week feeding trial was conducted to investigate the effects of dietary crystalline methionine (CMet) and OMet on the growth performance, feed utilization and protein metabolism responses of juvenile large yellow croaker (Larimichthys crocea) with initial body weight of (26.0±1.6) g. A practical diet with low fish meal content (31.8%) was used as the control diet (LF). Six other experimental diets (CMet 0.35, CMet 0.65, CMet 0.95, OMet 0.35, OMet 0.65, and OMet 0.95) were formulated with 0.35%, 0.65% and 0.95% CMet or OMet respectively. The weight gain rate (WGR) of fish treated with OMet or CMet was significantly higher than control and increased significantly along with the elevated level of supplement (P<0.05). The WGR was the highest in fish treated with OMet 0.95. The WGR and protein efficiency ratio (PER) of fish in OMet treatment were significantly higher than those treated with CMet (P<0.05). In all treatments there was no significant difference in survival rate, feed conversion ratio or body composition (crude protein, crude lipid, ash, and moisture, P>0.05). Compared to CMet treatment, OMet caused lower hepatosomatic index (HSI) and higher activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in the liver (P<0.05). Meanwhile, the methionine level greatly affected activities of GOT. The fish in OMet 0.95 treatment showed the lowest HSI and the highest GPT and GOT activities. However, in all groups no significant difference was detected in the concentrations of ammonia and urea nitrogen in the serum (P>0.05). This study indicated that compared to CMet, OMet might be more effective in improving the growth performance and feed utilization of large yellow croakers, therefore could replace the former as the external methionine source to balance the amino acids in the soybean protein feed.