Evaluating fermented fish viscera silage in diets for Colossoma macropomum and its effects on physical quality of pellets, production performance, health parameters, and economic analysis

Abstract

The production of silage preserves fish viscera using simple techniques and allow the reutilization of nutrients that are usually discarded; thus, promoting circular aquaculture. The aim of this study was to evaluate the inclusion of increasing levels of fish viscera silage on the physical quality of the feed pellets, and the growth performance, health parameters, and economic analysis when tambaqui (Colossoma macropomum) were offered the experimental diets. A fermented fish viscera silage (5% yogurt; 15% molasses; 0.25% antioxidant) was included in the formulation at graded levels in a wet-basis (VS 0%, VS 5%; VS 10%; VS 15%, and VS 20%). Tambaqui (initial weight ~ 22.6 g) were stocked in a recirculation system and fed the experiment diets to apparent satiation for 13 week. At the end of the feeding trial, fish presented ~ 500% growth for all experimental groups. Average feed efficiency was 0.78, protein efficiency rate 2.28%, and relative growth rate 1.79%.day− 1. Fish fed with the highest level of inclusion of viscera silage showed high concentrations of plasma cholesterol but with acceptable values for this species. The inclusion of fish viscera silage in diets for juveniles of tambaqui reduced the activity of the ALT enzyme, confirming normal liver function. Diets with fish viscera silage had a production cost of US$ 0.95 per kg, without significantly impacting on the economic indices. Up to 20% of fish viscera silage can be included in the extruded feed formulation to juveniles of tambaqui, without impairing growth performance and health parameters.