Tiny Worms, Big Potential: Enchytraeus albidus (Annelida: Clitellata) as Starter Feed for Rainbow Trout

Summary

The aquaculture industry is seeking sustainable feed alternatives to enhance the health and growth of farmed fish during their early life stages. Live feed, such as the annelid worm Enchytraeus albidus, has been shown to increase growth in marine fish species. This study evaluates E. albidus as a potential starter live feed for rainbow trout fry (Oncorhynchus mykiss), focusing on growth, health, and fatty acid composition. Fry were fed one of three diets: standard dry feed (DF), live E. albidus (EF), or a combination (DF/EF) for 21 days, followed by a transition to DF for the following 22 days. Fry initially fed with EF exhibited higher growth rates compared to those on DF, and they maintained superior size even 3 weeks after being transitioned to DF. At the end of the experiment, the fish fed EF had a 10% higher mass than fish fed DF. No significant differences were found in health indicators across the treatment groups, which all demonstrated good health and low mortality. The fatty acid profiles differed between treatments, with lower essential fatty acid docosahexaenoic acid (DHA) levels in fish fed EF. However, despite the lower body levels, critical DHA levels seemed to be preserved in the neural tissues of the fry. These findings highlight the potential of E. albidus as an effective starter feed for rainbow trout fry.