Dietary vitamin C requirement of juvenile Chinese sucker (Myxocyprinus asiaticus)

An 8‐week growth experiment was conducted to quantify the appropriate dietary vitamin C requirement of juvenile Chinese sucker (Myxocyprinus asiaticus). Triplicate groups of 30 experimental fish [initial body weight: (7.1 ± 0.3) g] were cultured in 500 L aquaria and fed with semi‐purified diets containing six levels [10.1 (unsupplemented diet), 37.4, 64.9, 125.2, 244.2 and 482.0 mg kg^?1 diet, respectively] of vitamin C (supplied as L‐ascorbyl‐2‐polyphosphate). Results showed that weight gain of Chinese sucker was significantly increased with increasing dietary vitamin C levels, but there was no significant difference of weight gain among fish fed the diets containing more than 125.2 mg kg^?1 vitamin C. As dietary vitamin C increased, the liver vitamin C content of fish showed the increasing trend firstly and then stabled, while the muscle vitamin C content significantly increased without reaching a constant level. Lower liver malondialdehyde content was observed in 125.2, 244.2 and 482.0 mg kg^?1 vitamin C groups, and higher antioxidant capacity and superoxide dismutase activities were observed in supplemented groups when compared to the unsupplemented group. Liver aspartate aminotransferase and alkaline phosphatase activities were also significant affected by dietary vitamin C. Ash content of fish fed the diet with 244.2 or 482.0 mg kg^?1 vitamin C was significantly higher than that of fish fed the other diets. However, dietary vitamin C had no significant effects on whole‐body crude protein, lipid and moisture contents. The vitamin C requirement of juvenile Chinese sucker was estimated to be 84.6 and 126.1 mg kg^?1 based on weight gain and liver vitamin C concentration respectively.     

胭脂鱼仔鱼的生长和消化酶活力变化

对胭脂鱼(Myxocyprinus asiaticus)孵化后1～37 d仔鱼的体长、体重、RNA/DNA比率、胰蛋白酶、脂肪酶和淀粉酶的酶活力变化进行了测定。结果显示:胭脂鱼仔鱼1～37 d体长稳定增长。体重增加呈阶段性,在1～21 d体重增长缓慢,21～29 d体重增加较快,29～37 d体重快速增加。仔鱼从7 d开始摄食,1～6 d,RNA/DNA比率变化很小,蛋白含量逐渐降低;7～21 d,RNA/DNA比率波动较大,蛋白含量增长缓慢;21～37 d,RNA/DNA比率和蛋白质均增长迅速。生长率(GR)与RNA/DNA比率的回归方程为:GR=1.01RNA/DNA+1.6077(R2=0.8516)。从2、5和7 d开始分别检测到明显的胰蛋白酶、脂肪酶和淀粉酶活力,之后,消化酶活力随着发育先快速地上升然后波动性地下降到一个稳定水平。结果表明:胭脂鱼仔鱼从内源性到外源性营养转化过程中,不同的消化酶能够检测到明显酶活力的时间不同,到仔鱼开始摄食时已经具备消化蛋白质、脂肪和淀粉的能力;RNA/DNA比率可以作为判定仔鱼生长率的可靠指标。     

溶解气体过饱和水体对胭脂鱼血气平衡影响初步研究

针对向家坝库区溶解性气体过饱和对鱼类的影响,开展溶解性气体过饱和自然水域中胭脂鱼（ Myxocyprinus asiaticus）的血气酸碱平衡的分析研究。结果表明,中度染毒组血液（暴露于溶解气体饱和水体2 h）碳酸氢根浓度（AB）、标准碳酸氢盐浓度（SB）、二氧化碳含量（TCO2）水平显著下降,全血碱超（BEb）、细胞外液碱超（BEecf）负值显著增加, pH、氧分压（ pO2）、二氧化碳分压（ pCO2）、血氧饱和度（ SO2）均下降,半饱和度氧分压（ p50）显著升高;重度染毒组（暴露于溶解气体饱和水体4 h） AB、 SB、 TCO2、 pH、 SO2均显著下降, BEb、 BEecf负值均显著增加, pO2、 pCO2均升高, p50显著升高;溶解气体过饱和水体引起胭脂鱼发生酸中毒。     

饲料脂肪水平对胭脂鱼幼鱼生长、体组成和抗氧化能力的影响

试验选用体重(6.73±0.21)g的胭脂鱼(Myxocyprinus asiaticus)幼鱼540尾,随机分成6个组,每组3个重复,每个重复30尾试验鱼。以大豆油为脂肪源,配制成脂肪水平为2.04%、4.43%、6.88%、9.02%、11.98%、13.39%的半精制饲料,进行为期56 d的生长试验,研究脂肪水平对胭脂鱼幼鱼生长、体组成及机体抗氧化能力的影响。结果显示:饲料脂肪水平对胭脂鱼的生长性能有显著影响(P<0.05)。脂肪水平为6.88%时,胭脂鱼增重率、特定生长率、蛋白质沉积效率最高,饲料系数最低。脂肪沉积效率随脂肪水平的增加呈下降趋势。随脂肪水平增加,胭脂鱼全鱼、肌肉和肝胰脏脂肪含量逐渐上升,至6.88%组后稳定,而全鱼水分、粗蛋白含量没有显著变化(P>0.05)。胭脂鱼机体抗氧化能力随着脂肪水平的增加呈现先升后降趋势,脂肪水平为6.88%时,总抗氧化能力(T-AOC)、超氧物歧化酶(SOD)值最大,丙二醛(MDA)值最小,即抗氧化能力最强。以增重率、特定生长率和饲料系数进行回归分析并考虑脂肪水平对胭脂鱼营养组成和抗氧化能力的影响,确定胭脂鱼幼鱼适宜脂肪水平为6.62%~7.02%。