Effects of vitamin A on growth performance, body composition and serum transaminase activities in the juvenile grass carp (Ctenopharyngodon idella) | 维生素A对草鱼幼鱼生长、体成分和转氨酶活性的影响

صينى. 研究VA对草鱼幼鱼生长、体成分和转氨酶活性的影响，以确定草鱼饲料中VA适宜的添加量。采用酪蛋白和脱脂豆粕为蛋白源、白糊精为糖源、玉米胚芽油和大豆油为脂肪源的半纯化饲料作为基础饲料，配制VA水平为0（对照组），810，1 620，2 520，3 224，3 980，7 950，16 386 IU/kg的8组试验饲料，饲养初始体质量为（10.79±0.52）g的草鱼12周，每组3个重复，每重复40尾，试验结束后测算体质量增长率、特定生长率、饲料系数、鱼体营养成分以及血清中碱性磷酸酶（ALP）、谷丙转氨酶（GPT）和谷草转氨酶（GOT）活性等指标。对照组的草鱼幼鱼，在试验后期有8.33%出现眼球突出、尾鳍充血的症状，添加VA试验组的草鱼未出现类似症状；饲料中VA含量在0～1 620 IU/kg时，体质量增长率随饲料中VA增加而显著增加（P＜0.05），饲料中VA含量7 950 IU/kg时，体质量增长率显著降低（P＜0.05）；特定生长率的变化趋势与体质量增长率类似，而饲料系数变化趋势与体质量增长率相反；VA对草鱼成活率和全鱼水分、蛋白质、脂肪、灰分含量无显著性影响（P＞0.05）；饲料中缺乏VA会显著降低血清中ALP的活性，同时显著提高GPT和GOT的活性（P＜0.05）。在本试验条件下，饲料中缺乏VA会引起草鱼幼鱼眼球突出、尾鳍充血和肝功能异常，饲料中添加适量的VA会促进草鱼的生长，降低饲料系数，但过量的VA会降低草鱼幼鱼的生长速度。对草鱼体质量增长率与饲料中VA含量进行折线回归分析，可知草鱼幼鱼获得最佳生长时对VA的需要量为1 653 IU/kg，同时建议饲料中VA含量不宜超过7 950 IU/kg。

إنجليزي. This experiment was conducted to reveal the effects of the dietary vitamin A on growth, body composition and transaminase activities in the juvenile grass carp (Ctenopharyngodon idella), to determine optimal dietary vitamin A of feed. Casein and defatted soybean were the source of protein and white dextrine was the source of carbohydrate. Retinol acetate was used as dietary vitamin A source to formulate semipurified diets at eight vitamin A levels (0, 810, 1 620, 2 520, 3 224, 3 980, 7 950 and 16 386 IU/kg, respectively). Each experimental diet was fed to triplicate groups of 40 fish with initial average weight (10.79±0.52) g for 12 weeks. Weight gain rate, special growth rate, feed conversion rate, body compositions and part transaminase activities in serum were detected at the end of breeding experiment. About 8.33% fish fed with diet without vitamin A exhibited exophthalmos and haemorrhages on the skin overlaying the base of the caudal fin. None of these deficiency signs was observed in fish fed with vitamin A supplemented diets. Weight gain rate and special growth rate significantly increased when dietary vitamin A level was less than 1 620 IU/kg (P＜0.05). When dietary vitamins A exceeded 7 950 IU/kg, the above indices significantly decreased (P＜0.05). The reverse trend appeared in feed conversion rate. The whole body compositions and survival rate were not affected by dietary vitamin A levels. When diet lacked vitamin A, the activity of alkaline phosphatase was significantly decreased (P＜0.05), but the activities of glutamic propylic transaminase and glutamic oxaolacetic transaminase were significantly increased in serums (P＜0.05). Results of the above showed that when diet lacked vitamin A, the grass carp could be caused exophthalmos, congestion and abnormal liver function, and added vitamin A could improve growth performance, whereas, overdose vitamin A could decrease the growth. Broken-line regression analysis showed that juvenile grass carp requires a minimum of 1 653 IU/kg diet for maximal growth, and should not exceed 7 950 IU/kg diet.