维生素A对养成期草鱼生长性能以及骨骼中钙磷含量变化的影响

实验旨在探究养成期草鱼对饲料中维生素A的需求及维生素A对养成期草鱼的骨骼中钙磷含量的影响。选取养成期（254.6±0.5）g草鱼420尾，随机分为7组，每组3个重复，每个重复20尾。分别用维生素A含量为89、732、1129、2378、4688、7218和9802 IU/kg的等氮等能实验饲料喂养84d。实验结果表明:（1）饲料中添加4688 IU/kg的维生素A显著提高了养成期草鱼的特定生长率（P < 0.05），并显著降低了饲料系数（P < 0.05），但饲料维生素A含量对鱼体摄食率、成活率以及肝脏指数没有显著影响（P>0.05）。（2）饲料添加维生素A对鱼体粗蛋白、粗脂肪、灰分没有显著影响（P>0.05），但是9802 IU/kg组的鱼体水分显著低于其他实验组（P < 0.05）。（3）饲料中4688 IU/kg的维生素A显著提高血清中超氧化物歧化酶的活性（P < 0.05），但饲料维生素A水平对血清丙二醛、钙、磷含量以及碱性磷酸酶活性没有显著影响（P>0.05）。（4）饲料添加4688和7218 IU/kg的维生素A能显著提高草鱼头骨和脊椎骨中灰分以及钙、磷含量（P < 0.05）。在实验条件下，以特定生长率、饲料系数以及血清SOD活性为评价指标，通过折线分析得出养成期草鱼适宜维生素A的需求量分别为3184和3077 IU/kg。

EFFECTS OF DIETARY VITAMIN A ON GROWTH PERFORMANCE AND CALCIUM AND PHOSPHORUS CONTENTS IN BONE OF SUBADULT GRASS CARP (CTENOPHARYNGODONIDELLUS)

To determine the optimum dietary requirement of vitamin A (VA) of subadult grass carp (Ctenopharyn-godon idellus), seven isoenergetic and isonitrogenous semi-purified diets were formulated to contain VA level at 89, 732, 1129, 2378, 4688, 7218 and 9802 IU/kg diet respectively, for a 12-week growth trial that was conducted in 21 net-cages located in an earth pond. The results indicated that dietary VA level significantly regulated the specific growth rate (SGR) and feed conversion ratio (FCR) of subadult grass carp (P<0.05) with the highest SGR and the lowest FCR both in 4688 IU/kg group. Feeding rate, survival rate and hepatosomatic index were not affected by dietary VA level (P>0.05). Dietary VA level showed significant (P<0.05) effect on serum SOD activity with the highest SOD values in 4688 IU/kg group. Serum ALP activity, MDA, calcium (Ca) and phosphorus (P) contents were not significantly (P>0.05) affected by dietary VA level. Body moisture content in 9802 IU/kg group was significantly lower. Body lipid, protein and ash contents were not affected by dietary VA level (P>0.05). The ash contents either in skull or in vertebra were significantly affected (P<0.05) by dietary VA level. The higher Ca and P contents in skull and vertebra were both observed in 4688 and 7218 IU/kg groups (P<0.05). Broken-line analysis for the SGR of fish suggested that the optimal dietary VA content for subadult grass carp was 3184 IU/kg diet.