维生素E对青鱼幼鱼生长、免疫及抗氨氮胁迫能力的影响

EFFECTS OF VITAMIN E SUPPLEMENTATION ON GROWTH, IMMUNITY OF JUVENILE BLACK CARP (MYLOPHARYNGODON PICEUS) SUBJECTED TO AMMONIA-NITRITE STRESS

以初始体质量(7.27±0.40)g的青鱼为研究对象,采用维生素E(VE)有效含量分别为14.36(对照组)、25.14、37.66、62.97、113.92和210.45 mg/kg 6种等氮等能的实验饲料,饲养青鱼幼鱼8周后,根据生长情况选取对照组、62.97和210.45 mg/kg VE组进行24h氨氮胁迫(20 mg/L),研究VE对青鱼幼鱼生长、免疫及抗氨氮胁迫能力的影响。结果表明:以特定生长率为指标,折线模型分析表明青鱼有效维生素E需要量为45.00 mg/kg。肌肉、肝脏和血清VE含量与饲料中VE含量呈明显正相关,当饲料VE含量超过113.92 mg/kg时,肌肉和肝脏VE含量均达到饱和。VE对鳃丝Na+/K+-ATP酶活性(NKA)和血清皮质醇(COR)无显著影响,但随着饲料VE含量的升高,过氧化氢酶(CAT)和总超氧化物歧化酶活性(T-SOD)呈上升趋势,丙二醛含量(MDA)呈下降趋势。氨氮胁迫对各处理组肌肉VE含量和血清CAT活性无影响,但肝脏VE含量均显著降低(P<0.05),且62.97和210.4 5 mg/kg VE组血清VE水平有所升高。在胁迫后,对照组血清T-SOD、鳃丝NKA活性显著降低,皮质醇含量显著增加(P<0.05)。与对照组相比,62.97和210.45 mg/kg VE组T-SOD、NKA活性和皮质醇含量在胁迫前后无显著变化。各处理组MDA含量在胁迫后虽均显著升高,但210.45 mg/kg VE组在胁迫后MDA含量仍显著低于对照组(P<0.05)。以上结果说明,青鱼幼鱼获得最大生长的有效维生素E需求量为45.00 mg/kg,且较高VE能有效提高青鱼机体免疫力,缓解氨氮胁迫对青鱼机体的负面影响。

An 8-week feeding experiment was conducted to evaluate the effects of dietary vitamin E （VE） supplementation on growth, immunity of juvenile black carp[initial average weight of （7.27±0.40） g] subjected to ammonia-nitrite stress. Six practical diets were formulated to contain 14.36 （control）, 25.14, 37.66, 62.97, 113.92, and 210.45 mg vitamin E equivalent/kg diet, supplied as VE acetate. After feeding for 8 weeks, according to growth, the black carp in control, 62.97 and 210.45 mg/kg vitamin E treatment groups were selected and subjected to ammonia-nitrite stress （20 mg/L） for 24h. The results indicated that the dietary VE content for the maximum specific growth rate （SGR） was about 45.0 mg/kg. The vitamin E levels in the tissues of liver, muscle and the serum were positively correlation with diet vitamin E content, and no significant differences were observed among fish fed with the diets that had equal to or higher than 113.92 mg/kg of vitamin E. No significant difference in gill Na＋/K＋-ATPase （NKA） activity were observed among these treatments. However, with increasing diet vitamin E content, activities of total superoxide dismutase （T-SOD） and catalase （CAT） increased, and malondialdehyde （MDA） content decreased. Each group of muscle vitamin E concentration and CAT activity were not affected by ammonia-nitrite stress, although liver vitamin E concentration decreased significantly and serum VE level increased in the 62.97and 210.45 mg/kg VE treatments. After the stress, T-SOD and gill NKA activities in the control group decreased significantly and cortisol content increased significantly （P〈0.05）. In comparison, activities of T-SOD, NKA and cortisol showed no significant changes. MDA content in each group increased significantly after stress. However, for the 210.45 mg/kg VE treatment group, MDA content was significantly lower than the control group （P〈0.05）. Our results indicated that the effective VE requirement of juvenile black carp for optimal growth may be 45.0 mg/kg diet, and higher vitamin E in diet could improve non-immune response and anti ammonia-nitrite stress ability of black carp.