Effects of micro-algae oil replacement on growth, omega-3 deposition and gut microbiome composition of Nile tilapia (Oreochromis niloticus)

Abstract

Microalgae offer a sustainable source of omega-3 fatty acids that can replace fish oil in aquafeeds, but the nutritional benefits are not always clear, particularly when microalgae are used as complete oil replacements in starter feeds. We compared the survival, growth, omega-3 deposition and composition of the gut microbiota of Nile tilapia fed with aquafeeds that differed in dietary oil, from plant, fish and microalgae (Schizochytrium) origins. Survival was not affected by diet, but fish fed a diet where the entire oil component (5%) was replaced by microalgae oil grew twice as fast than fish fed plant oil or a mixture of plant and fish oil. Dietary omega-3 content was strongly correlated with omega-3 deposition in the fish fillet. Complete replacement of fish oil by plant oil caused a significant increase in the abundance of Aeromonadaceae which is often associated with an inflammatory response in the fish gut. In contrast, when fish oil was replaced by microalgae oil an increase in Peptostreptococcaceae and Mycobacteriaceae was observed. Our study indicates that Schizochytrium oil can be used to improve the growth of Nile tilapia and increase its omega-3 content without any of the detrimental effects on the gut microbiome typically associated with some plant oil replacements.