本试验旨在研究饲料中维生素D₃添加水平对黄鳝生长性能及免疫功能的影响。挑选体质健康、平均体重为(21.7±2.1) g的黄鳝540尾,随机分为6组(每组3个重复,每个重复各30尾),分别饲喂在基础饲料中添加0(对照组)、250、500、1 000、2 000和4 000 IU/kg维生素D₃的试验饲料,试验期90 d。饲养试验结束后,从每组随机取6尾黄鳝,测定生长性能后尾静脉取血检测外周血相关免疫指标;另从每组随机取20尾黄鳝,注射嗜水气单胞菌菌液进行攻毒试验,观察嗜水气单胞菌攻毒后的累积死亡率。结果表明:与对照组相比,除4 000 IU/kg组外,其余各组增重率和蛋白质效率显著提高(P<0.05),饲料系数显著降低(P<0.05);500和1 000 IU/kg组血清免疫球蛋白M、补体3、补体4水平,溶菌酶活性,T细胞CD3、CD4、CD8分子数量和CD4/CD8显著升高(P<0.05),全血白细胞、中性粒细胞、中值细胞和淋巴细胞数量显著升高(P<0.05),且嗜水气单胞菌攻毒后的累积死亡率明显降低。4 000 IU/kg组除血清免疫球蛋白M水平外,其他指标与对照组均无显著差异(P > 0.05)。由此得出,饲料中添加适宜水平(500和1 000 IU/kg)的维生素D₃能增强黄鳝的免疫功能,提高其对病菌的抵御能力;饲料中维生素D₃水平过高或缺乏均会导致黄鳝免疫功能低下。

This experiment was conducted to study the effects of vitamin D₃ supplemental level on growth performance and immune function of Monopterus albus. A total of 540 healthy M. albus with an average body weight of (21.7±2.1) g was randomly assigned to 6 groups with 3 replicates per group and 30 M. albus per replicate. The M. albus in the 6 groups were fed with the basal diet supplemented with 0 (control group), 250, 500, 1 000, 2 000 and 4 000 IU/kg vitamin D₃, respectively. After 90 days feeding, researchers randomly selected 6 M. albus in each group, and drew blood from caudal vein to detect the related immune indexes of peripheral blood after growth performance determination. Furthermore, researchers injected Aeromonas hydrophila into 20 M. albus randomly selected in each group to observe the cumulative mortality of the M. albus challenged with A. hydrophila. The results showed as follows: compared with the control group, except 4 000 IU/kg group, the weight gain rate and protein efficiency ratio in other groups were significantly improved (P<0.05), and feed conversion ratio was significantly decreased (P<0.05); in 500 and 1 000 IU/kg groups, the levels of immunoglobulin M, complement 3 and complement 4, the activity of lysozyme, and the amounts of CD3, CD4 and CD8 of T cells with CD4/CD8 in serum were increased significantly (P<0.05), in addition the number of whole blood leukocyte, neutrophil, intermediate cell and lymphocyte was significantly increased (P<0.05), moreover, the cumulative mortality of the M. albus challenged with A. hydrophila was obviously decreased. No significant differences were found in all indexes except serum immunoglobulin M level between 4 000 IU/kg group and control group (P>0.05). In conclusion, supplementation of appropriate (500 and 1 000 IU/kg) vitamin D₃ can enhance humoral immunity, cellular immunity and nonspecific immunity function of M. albus, thus improving the resistance ability to pathogenic bacterium; moreover, lack or excessive supplementation of vitamin D₃ can result in the lower immune function of M. albus.