Effects of fish oil replacement by a combination of soybean and palm oil in Asian seabass (Lates calcarifer) diet on growth, fatty acid profile, digestive enzyme activity, immune parameters and salinity challenge

Abstract

The experiment was in completely randomized design. Seven iso-nitrogenous and iso-lipidic diets were formulated having soybean and palm oil, an equal combination, to replace fish oil (FO) in diets at 0%, 25%, 37.5%, 50%, 62.5%, 75%, and 100%, respectively. Each diet was fed twice daily to Asian seabass juvenile (3.00±0.26g) in quintuplicate for eight weeks and performances were investigated. Finally, the fish were challenged with 30 ppt salinity to observe osmoregulatory responses. Zero mortality was observed in all feeding groups. Fish growth responses, diet consumption and feed conversion ratio were significantly affected (p<0.05). Crude lipid and viscerosomatic index of final fish were influenced (p<0.05). Fatty acid profiles of the whole-body reflected the dietary intake. Arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3), docosahexaenoic acid (22:6n-3) and n-3/n-6 ratio were better in fish fed 37.5% FO replaced diet. Specific digestive enzyme activities in stomach, pyloric caeca and intestine were unaffected (p˃0.05). White blood cells, respiratory burst activity and serum protein were influenced by the diets (p<0.05). For salinity challenge, similar osmoregulatory responses were observed among the dietary groups. In short, the combination of soybean and palm oil substituted 75% FO in Asian seabass juvenile diet without affecting growth performance and health status.

Keywords

• alternative lipid source
• asian seabass
• growth
• fatty acid profile
• salinity challenge