Productive performance and liver and splenic histology of yellowtail lambari supplemented with propolis in a water recirculation system

We analyzed the effects of propolis on the productive performance and histological responses of fingerling yellowtail lambari (Astyanax altiparanae). Fish were distributed in twelve tanks,10 fish per replicate, and were acclimated for one week in a recirculation water system RAS and fed three times a day (9, 11, and 13h) with commercial extruded feed for omnivorous fish. The water quality parameters were considered acceptable for tropical fish. Before the experimental period, a total of 120 fish (1.11 ± 0.26 g, 4.4 ± 0.4 cm) fed a diet containing Propolis Alcoholic Extracts for 35 days, distributed in following groups: T0 (control group); T1 (green propolis), T2 (brown propolis), and T3 (red propolis), with 10 fish per repetition, were tested in triplicate. After this, all fish were weighed and measured to assess productive performance, and liver and spleen samples from 2 fish per replicate (n = 6 per treatment) were sent for histological analysis. As a result, the fish supplemented with green and red propolis showed better weight gain, feed conversion, feed efficiency, biomass, and specific growth rate compared to the group fed brown propolis and the control group. The survival of the lambari in groups T1, T3, and the control was 100%, except in T2, which was equal to 86.67%. Fish supplemented with treatments containing green, brown, and red propolis showed mild hepatic and splenic alterations, suggesting that propolis, regardless of the extract type, was well metabolized by yellowtail lambari. Based on the results of this study, dietary propolis supplementation for 35 days improved weight gain, feed conversion, feed efficiency, specific growth, final biomass, and caused mild histological alterations in the liver and spleen tissues of the fish. Our results could positively impact the lambari aquaculture by providing a new sustainable feeding protocol based on green and red propolis.