水解单宁对暗纹东方鲀摄食偏好、消化代谢和抗氧化能力的效应

为了解菜粕替代鱼粉后单宁的作用,配制4组等氮等能饲料饲喂初重(39.84±3.09) g的暗纹东方鲀8周。以含43%鱼粉的实用基础饲料T0为对照;另设置3个不同的鱼粉用量组,用酪蛋白平衡蛋白质含量,并添加0.25%(T1)、0.75%(T2)和1.25%(T3)的水解单宁,使酪蛋白:水解单宁≈菜粕中蛋白含量:菜粕中单宁含量=16.8∶1。结果显示,随饲料中水解单宁添加量的增加,增重率呈上升趋势,饲料系数显著下降;肌肉粗脂肪含量T2组显著高于T0及T1组,对照组氨基酸水平显著高于其他组。肝脏抗氧化指标中,T0组过氧化氢酶(CAT)活力显著低于其他组,总抗氧化能力(T-AOC)则显著高于其他组,T3组丙二醛(MDA)含量和超氧化物歧化酶(SOD)活性显著高于其他组。血清抗氧化指标中,3个单宁组MDA含量均显著高于对照组,过氧化氢酶(CAT)活力显著下降。随饲料中水解单宁添加量的增加,血清谷丙转氨酶(ALT)活性先升后降,与肝脏中趋势一致;T1组白蛋白(ALB)含量高于T0及T3组,显著高于T2组,T1组总蛋白(TP)含量高于T0组,显著高于T2及T3组。T1及T2组肠道淀粉酶活性显著高于T0组,胃和肠道中的蛋白酶活性随水解单宁添加量的增加显著上升,胃脂肪酶活性显著下降。T3组苦味受体T2R1表达量在舌尖和肠道均显著高于对照组;肝脏热休克蛋白HSP70表达量T0组显著高于T3;摄食偏好实验中,驯化前暗纹东方鲀摄食偏好随水解单宁添加量的增加显著下降,驯化8周后,4组实验鱼对T2饲料的偏好程度均显著高于T0,T0饲料高于T1和T3组。研究表明,添加1.25%及以下水解单宁对暗纹东方鲀生长无负面影响,一定程度上对饲料有节约作用;添加水解单宁会改变鱼体对蛋白质、脂肪和糖类的消化及蛋白质合成代谢,添加量在1.25%时会损伤抗氧化能力和抗应激能力;用含有水解单宁的饲料驯化暗纹东方鲀可显著提高其对水解单宁添加量为0.75%的饲料的偏好程度,并提高对苦味的接受能力。

Effects of supplemental hydrolysable tannin on feeding preference, nutrition digestion and antioxidant ability of obscure puffer (Takifugu fasciatus)

Total 720 Takifugu fasciatus (initial weight 39.84 ±3.09 g) were fed with four isonitrogenous and isoenergetic semi-purified diets for eight weeks:control diet (T0) with hydrolysable tannin-free protein sources (containing 43% fish meal) and three experimental diets supplemented with 0.25%, 0.75%, and 1.25% hydrolysable tannin (called T1, T2, and T3, respectively). In experimental diets, crude protein content was balanced by casein when fish meal level decreased, and the ratio of casein to tannin was nearly equal to that of protein content to tannin content in rapeseed meal (16.8:1).The results showed that the weight gain rate was not influenced, while feed coefficient ratio decreased significantly with increasing tannin level; the muscle crude lipid of T2 was significantly higher than those of T0 and T1, and the amino acid level of T0 was significantly higher than other groups; for liver antioxidant index, the activity of catalase (CAT) in T0 was significantly lower than other groups, while total antioxidative capacity (T-AOC) in T0 was significantly higher than other groups, the activity of superoxide dismutase (SOD) and the content of malonaldehyde (MDA) in T3 was significantly higher than other groups; for serum antioxidant index, the activity of SOD showed no significantly difference (P > 0.05), while the content of MDA in T0 was significantly lower than other groups, and the activity of catalase (CAT) decreased with increasing tannin level; for serum biochemical indices, the activity of ALT first increased, and then decreased at T2, paralleling the result of ALT in liver, the content of album (ALB) in T1 was higher than T3 (P > 0.05) and T1 was significantly higher than T0 and T3 groups, the total protein (TP) content of T1 was higher than T0, and T1 was significantly higher than T2 and T3; the activity of intestinal amylase in T1 and T2 groups were significantly higher than T0, the activity of protease increased with increasing tannin level in both stomach and intestine, the activity of lipase decreased in stomach; the expression of T2R1mRNA in T3 was significantly higher than T0 both in tongue and intestine(P<0.01); the expression of HSP70 mRNA in liver in T0 was significantly higher than T3. Furthermore, the preference decreased with increasing tannin level before feeding test, while after 8-week domestication, the fish preferred to diet containing 0.75% tannin in all groups. In conclusion, feeding obscure puffer with diet containing no more than 1.25% supplemental hydrolysable tannin would not decrease growth and feed coefficient ratio, while it would change the digestion of protein, lipid, carbohydrate and anabolism of protein, and when the amount of supplemental hydrolysable tannin was up to 1.25%, antioxidant ability and anti-stress ability were both damaged.