Evaluation of the enzymatic hydrolysis of sargassum mixed with fish protein hydrolysis product as an alternative protein source in shrimp feed, from the perspectives of growth performance, amino acid composition, antioxidant capacity and endoplasmic reticulum stress

A study was conducted to evaluate the effect of enzymatic hydrolysis of sargassum mixed with fish protein hydrolysis product (named “SFPH” in the present study) as a substitute for fish meal in shrimp feed. Six isonitrogenous and isolipidic diets (SFPH was used to replace 0 %, 5 %, 10 %, 20 %, 30 % and 40 % of fish meal protein) were administered to Litopenaeus vannamei (initial body weight: 0.9 g) for 8 weeks. Results showed that SFPH can replace 30 % of fish meal without affecting the growth performance of shrimp. However, 40 % of SFPH substitution significantly inhibited the weight gain rate (WGR) and specific growth rate (SGR) of shrimp. SFPH substitution had little effect on the composition of fatty acids, but SFPH substitution significantly reduced the contents of histidine, phenylalanine, tyrosine and taurine in the whole shrimp body. SFPH improved the structure of shrimp hepatopancreas and muscle when no more than 20 % of the fish meal was replaced. However, 40 %SFPH substitution significantly disrupted the structure of hepatopancreas and muscle. SFPH substitution significantly affected the antioxidant capacity, as manifested by a gradual decrease in T-AOC activity. With respect to endoplasmic reticulum stress, 30 %SFPH and 40 %SFPH groups significantly increased the mRNA expression of eif2α and bip. In summary, SFPH can replace 30 % of fish meal protein in shrimp feed without affecting shrimp growth. However, when SFPH exceeds 30 %, it can easily induce oxidative stress and endoplasmic reticulum stress in the hepatopancreas.