Evaluation of IMTA-produced seaweeds (Gracilaria, Porphyra, and Ulva) as dietary ingredients in Nile tilapia, Oreochromis niloticus L., juveniles. Effects on growth performance and gut histology

Abstract

The present study evaluated the effects of the inclusion of three seaweeds, Gracilaria vermiculophylla (GRA), Porphyra dioica (POR), and Ulva spp. (ULV), as dietary ingredients for Nile tilapia (Oreochromis niloticus) juveniles, on the growth performance, body composition, and gut histology. Three experimental diets (GRA, POR, and ULV) were formulated to replace 10 % of whole diet by each of the three seaweeds. A control diet (CTRL) was used, without inclusion of any seaweed. Diets were fed to triplicate groups of 25 Nile tilapia juveniles, with an average body weight (ABW) of 12.1 g, in an 84-day trial. At the end of the trial, growth performance was significantly reduced (P < 0.05) in fish fed the GRA diet, whereas the feed conversion ratio increased significantly in those fish. None of the treatments caused adverse effects on body composition. The inclusion of the three seaweeds in the diet led to evident changes in the fish digestive system morphology with significant reduction of villi length on GRA diet. The results obtained in this study suggest the usefulness of P. dioica and Ulva spp. to partially replace fishmeal in practical diets for tilapia juveniles up to 10 %, as no negative consequences on growth performance or body composition were observed. However, the inclusion of 10 % G. vermiculophylla seems to have a negative effect in diet palatability, reducing fish feed intake and growth performance.