Effects of dietary eicosapentaenoic acid on the growth performance, fatty acid profile, immunity and heat tolerance of juvenile abalone Haliotis discus hannai Ino

A 93-day growth trial was performed to evaluate the influences of graded dietary EPA levels (0.03% (control group), 0.24%, 0.63%, 1.07%, 1.72% and 2.25%) on the growth performance, immunity and heat tolerance of juvenile abalone Haliotis discus hannai with a mean initial weight of 4.15 +/- 0.18 g. After the feeding trial, the findings found that the highest weight gain rate (WGR) belonged to the groups fed with 0.63% similar to 1.72% of dietary EPA (P < 0.05). The lowest feed conversion ratio was distinguished in the groups with 0.63% similar to 1.07% of dietary EPA (P < 0.05). Also, EPA supplementation in abalone feed increased the content of crude lipid in the soft body and the activity of lipase in the intestine (P < 0.05). The total antioxidative capacity increased when dietary EPA levels rose from 0.03% to 1.07%, and then decreased (P < 0.05). Furthermore, compared to the control group, the 0.24% and 0.24% similar to 0.63% of dietary EPA significantly down-regulated the mRNA levels of I kappa B kinase and kelch-like ECH-associated protein 1, respectively (P < 0.05). However, nuclear factor-kappa B and interleukin 1 receptor-associated kinase 4 genes expression in the digestive gland were significantly up-regulated by the use of 1.72% and 2.25% of EPA in diet (P < 0.05). The mRNA levels of tumor necrosis factor a and interleukin 16 were significantly up-regulated by the 2.25% of dietary EPA (P < 0.05). The 1.72% of dietary EPA significantly increased the falling rate of abalone after the heat stress compared with the control (P < 0.05). In conclusion, the optimal dietary EPA requirement of juvenile abalone was determined as 1.36% based on quadratic regression analysis against WGR. Moderate dietary EPA content (0.63% similar to 1.07%) improved the immunity and heat resistance of abalone. Excessive dietary EPA content (1.72% similar to 2.25%) decreased the growth, meanwhile, increasing the oxidative stress, inflammation and susceptibility of abalone to heat stress.

Automated summary

This study aimed to evaluate the effects of graded dietary EPA levels on the growth performance, immunity, and heat tolerance of juvenile abalone. It was found that moderate EPA content improved the immunity and heat resistance, while excessive EPA content decreased growth and increased oxidative stress and inflammation in abalone.