不同玉米淀粉水平对凡纳滨对虾肝胰腺脂肪代谢的影响

 采用8周的生长实验研究了以玉米淀粉为糖源的不同淀粉水平(w为10%、15%、20%、25%、30%、35%）对初始体质量为（0.96±0.02）g凡纳滨对虾的生长、体营养成分组成、肝胰脏显微结构和肝胰腺脂肪合成酶的影响。实验饲料中w(蛋白质)为38%;w(脂肪)＝5%。实验在室内循环水族箱内进行,实验用水为天然咸淡水（盐度：6‰～14‰）,6组饲料每组设3个重复,每箱30尾虾,饱食量投喂。实验结果表明:w(淀粉)＝15%实验组对虾的增质量率、SGR最高,分别为45362％和3.06,与w(淀粉)＝10%和w(淀粉)＝20%组无显著性差异,但明显高于其他各组;w〖WTBZ〗(淀粉)＝10%组的对虾成活率最高（96.67％）,w(淀粉)＝25％组最低（66.67％）;w(淀粉)在25%～35%时,对虾的增质量率、成活率、SGR显著低于w(淀粉)为10％、15％和20％组（P<0.05）。w(淀粉)＝20％组的体蛋白含量最低（72.24％）,w(淀粉)＝30％组最高（75.27％）,其余各组没有显著性差异;高淀粉组体脂肪含量相对较高。从凡纳滨对虾的肝胰脏组织学切片观察到,饲料w(淀粉)为10％～35％的范围内,肝胰脏脂肪无异常积累。肝胰腺中脂肪合成酶活性很低,苹果酸脱氢酶活性随饲料淀粉含量的增加而升高。总之,在饲料蛋白含量为w＝38%左右时,凡纳滨对虾饲料适宜的淀粉含量(w)为10％～20%。

Effects of Dietary Cornstarch Levels on Fat Metabolism of Hepatopancrease in Litopenaeus vannamei

The ability of Litopenaeus vannamei (initial mean weight: (0.96±0.02) g) to utilize different levels of cornstarch was examined in terms of growth indices, body composition, microscopic structure and lipogenic enzyme of the hapetopancreas. Six isonitrogenous semipurified diets were fed to shrimp to satiation for 8 weeks in triplicate tanks (30 shrimps per tank) connected to a natural brackish water (salinity: 6‰~14‰) recirculating system. Diets contained different levels of cornstarch (w,10%、15%、20%、25%、30%、35%) as the source of carbohydrate. Weight gain (WG), survival rate and SGR were considerably affected by cornstarch levels of diets. The highest weight gain (453.6％) and best SGR was observed in shrimp fed the 150 g·kg^-1 (cornstarch level) diet, and was significantly （P<0.05） higher than those fed diets containing 25% to 35% cornstarch. However, the survival rate reached maximum in shrimp fed the 10% diets（96.7％）, some 300 g·kg^-1 diets higher than the lowest rate, which was found in shrimp fed the 250 g·kg^-1 diets. Body lipid tended to be higher in shrimp fed diets with higher cornstarch levels. Besides, histological study on shrimp fed 10 to 35% diets exhibited no histological changes. Hepatopancreatic lipogenic enzyme activities (6PGDH, ME, IDH) in shrimp fed with different diets were very low; ME increased while carbohydrate levels increased. In a word, it is suitable for shrimp fed 10%~20% carbohydrate when the diets containing 38% protein.