酶解鱼溶浆和植物精油对大菱鲆幼鱼生长、肠道消化酶活力及TOR相关基因表达的影响

Effects of dietary stickwater hydrolysate and plant essential oils on growth performance,immunity,digestive enzyme activity and TOR related gene expression of juvenile turbot Scophthalmus maximus

为探究低鱼粉饲料中添加酶解鱼溶浆(stickwater hydrolysate,SWH)和植物精油对大菱鲆Scophthalmus maximus幼鱼生长、血清生化指标、肠道消化酶活性、抗鳗弧菌感染能力和雷帕霉素靶蛋白(TOR)相关基因表达的影响,以450尾初始体质量为37.67 g的大菱鲆幼鱼为研究对象,试验设置5个组,每组设3个重复,设计正对照组(鱼粉含量50%,D1)、负对照组(鱼粉含量30%,D2),以及在负对照组基础上分别添加1%酶解鱼溶浆(D3)、0.02%植物精油(D4)和1%酶解鱼溶浆+0.02%植物精油(D5)(饲料成分含量中的%均指质量分数),养殖幼鱼8周。结果表明:幼鱼增重率、特定生长率和蛋白质效率均在D3组达到最高值,显著高于其他组(P<0.05);D3和D5组饵料系数则显著低于负对照组(P<0.05);溶菌酶活力在D5组达到最高值,显著高于负对照组(P<0.05);C3酶活力在D5组达到最低值,显著低于其他组(P<0.05);幼鱼肠道胰蛋白酶活力在D3组达到最高值,显著高于负对照组(P<0.05);肝脏TOR mRNA相对表达量在D3组达到最高值,显著高于正、负对照组(P<0.05),而4EBP1和4EBP2 mRNA相对表达量则呈相反趋势;经鳗弧菌注射感染48 h后,D4和D5组鱼的累积死亡率显著低于负对照组(P<0.05)。研究表明,在鱼粉含量为30%的条件下,饲料中添加1%的酶解鱼溶浆,可显著促进大菱鲆幼鱼生长、肠道胰蛋白酶活性和TOR mRNA相对表达量,添加0.02%植物精油可提高幼鱼血清溶菌酶活性和抗鳗弧菌感染能力,但1%酶解鱼溶浆和0.02%的植物精油二者配伍对促进鱼体增重率的效果要低于单一添加1%酶解鱼溶浆,其相互作用机理还有待进一步研究。

The purpose of this experiment is to investigate the dietary stickwater hydrolysate(SWH)and plant essential oil on growth performance,immunity,digestive enzyme activity and TOR related gene expression of juvenile turbot Scophthalmus maximus fed low fish meal diets.Juvenile turbot with initial body weight of 37.67 g were reared in a closed water circulating system and fed diets containing 50%fish meal(D1,positive control),and containing 30%fish meal(D2,negative control),and 30%fish meal diets supplemented with 1%SWH(D3),0.02%plant essential oil(D4),and 1%SWH+0.02%plant essential oil(D5)with triplication at water temperature of(16±1)℃for 8 weeks.The results showed that there were significant increase in weight gain rate,specific growth rate and protein efficiency ratio and significant decrease in feed conversion ratio in the turbot in D3 group(P<0.05).The maximal activities of serum lysozyme was observed in the turbot in D5 group(P<0.05),significantly higher than that in the D2 group(P<0.05),without significant difference from D1 group(P>0.05).The turbot in D5 group had the minimal C3 content,significantly lower than that in other 4 groups(P<0.05).The maximal intestinal trypsin activity was found in the turbot juveniles in D3 group(P<0.05),significantly higher than that in the D2 group(P<0.05),without significant difference from D1 group(P>0.05).The maximal TOR mRNA expression level was observed in liver of fish in D3 group,significantly higher than that in the D2 and D1 groups(P<0.05),with an opposite trend in 4EBP1 and 4EBP2 mRNA expression levels(P<0.05).There was significantly lower cumulative mortality of juveniles exposed to Vibrio anguillarum infection at a dose of 7.94×105 CFU/g for 48 h in D4 and D5 groups than that in D2 group(P<0.05).It can be concluded that supplementation of 1%SWH led to significantly enhance the growth performance,trypsin activity,liver TOR related gene expression level of turbot,and that 0.02%plant essential oil to significantly enhance the ability of fish to resist V.anguillarum infection.However,the combination of 1%SWH and plant essential oil does not result in good effect instead of low weight gain,the mechanism of their interaction needs further research.