低鱼粉饲料中添加牛磺酸对青鱼幼鱼生长、肠道修复及抗急性拥挤胁迫的影响

为研究低鱼粉饲料中添加牛磺酸对青鱼幼鱼初始质量(5.90±0.03)g]生长、肠道修复及抗急性拥挤胁迫的影响,实验以青鱼正常鱼粉组(20%)为对照组,10%鱼粉组为负对照组(I_0组),在低鱼粉饲料中分别添加0.05%(I_(0.05)组)、0.1%(I_(0.1)组)、0.2%(I_(0.2)组)、0.4%(I_(0.4)组)牛磺酸,配制6种等氮等脂饲料,饲养8周。饲养实验结束后,参考生长结果,选择对照组、I_0组、I_(0.1)组、I_(0.4)组进行急性拥挤胁迫实验。结果显示:①与对照组相比,I_0组增重率显著下降,随着低鱼粉饲料中牛磺酸水平的升高,青鱼幼鱼增重率呈先上升后下降趋势,当牛磺酸添加量为0.1%时与对照组差异不显著;②相对于对照组,I_0组的绒毛高度降低、隐窝深度增加,杯状细胞数降低,添加牛磺酸使绒毛高度升高、隐窝深度降低,杯状细胞数和淋巴细胞数增多;③急性拥挤胁迫使青鱼幼鱼血清史质醇、血糖、血清溶菌酶(LSZ)、补体C3、超氧物歧化酶(SOD)和谷胱甘肽(GSH)含量均呈先升高后下降的趋势,其最大值出现在胁迫2 h或者8 h。在整个胁迫期间,I_0组史质醇和血糖含量高于其他各饲料组,I_0组溶菌酶、补体C3、SOD和GSH均低于其他各饲料组。研究表明,在低鱼粉饲料中添加牛磺酸可提高青鱼生长性能、改善肠道结构、增强青鱼的抗急性拥挤胁迫的能力。

Effect of dietary taurine supplementation on growth, intestine structure and resistance to acute crowding stress in juvenile black carp (Mylopharyngodon piceus) fed low fish meal diets

An 8-week feeding experiment was conducted to investigate the effects of dietary graded level of taurine supplementation on growth performance, intestine structure and resistance to acute crowding stress of juvenile black carp (Mylopharyngodon piceus) (initial mean body weight 5.90±0.03 g). The diet containing 20% fish meal was set as the control group. All the other groups contained 10% fish meal and were supplemented with 0% (I₀), 0.05% (I_0.05), 0.1% (I_0.1), 0.2% (I_0.2) and 0.4% (I_0.4) taurine, respectively. Each diet was randomly fed to triplicate groups of 30 fishes per tank (300 L). After the feeding experiment, according to growth performance, a 24 h acute crowding stress was conducted in 4 group (the control, I₀, I_0.1, I_0.4, and the density is 100 g/L. The results showed that the weight gain rate (WGR) of black carp in I₀ group was significantly lower than that in the control group (P<0.05). At the lower fish meal level, WGR of black carp first rose and then decreased with increasing dietary taurine supplementation level, and the maximum value was found in 0.1% group (P<0.05), who had no significant difference with the control group. Compared with the control, the villus height of the I₀ group were higher, crypt depth and number of goblet cells of the I₀ group were smaller; At the lower fish meal level, all fish fed the diets with dietary taurine supplementation had a greater crypt depth, goblet cell and lymphocytes number. Moreover, a lower villus height, villus height, crypt depth, goblet cell and lymphocytes number of intestine in the I_0.1 group were significantly higher than the control group (P<0.05). As the growth of the crowded stress time, cortisol, blood glucose (GLU) and lysozyme (LSZ), complement C3, superoxide dismutase (SOD) and glutathione (GSH) all had a trend of first rose and then decreased, and the maximum were found at 2 h and 8 h. There were different increase of these indexes among dietary treatments. The serum glucose and cortisol of fish fed the diet with 10% fish meal level were significantly higher than those in the other group (P<0.05), but serum LSZ, complement C3, SOD and GSH in I₀ group lower than those in the other group (P>0.05). These results suggested that dietary taurine supplementation can enhance growth performance of black carp, improve intestine structure, and increase the ability of black carp''s resistance to acute crowding stress.