Utilization of Tissue-Cultured Kappaphycus alvarezii Seaweed as a Raw Material for Fish Feed via Fermentation Technology

This study aimed to evaluate the effects of incorporating fermented Kappaphycus alvarezii powder, derived from tissue-cultured biomass and processed using various fermentative agents, into fish feed formulations. The research investigates its impact on feed protein quality, amino acid profile, as well as fish growth performance and survival rate. The research employed an experimental method comprising two stages. Stage 1: K. alvarezii seaweed flour fermentation was carried out using three fermenter treatments: EM4 at 2 mL/100 g, yeast at 1.5%, and a combination of EM4 + yeast (1 mL + 0.75% per 100 g). The resulting fermented seaweed flour was then used to produce fish feed with four different concentration treatments: 4%, 8%, and 12%, in addition to a control feed for comparison. The parameters analyzed included crude protein content and amino acid profile of feeds. Data were analyzed descriptively. Stage 2: A biological feed trial using the stage 1 feeds was conducted on the Nile tilapia (Oreochromis niloticus) over a 40-day culture period. The experimental design followed a factorial completely randomized design (CRD) with two factors: fermenter type (F) at three levels (EM4, yeast, and EM4 + yeast), and concentration of fermented K. alvarezii flour in the feed (K) at three levels (4%, 8%, and 12%), each replicated three times, resulting in a total of 27 treatment combinations plus a control feed treatment. The measured parameters included growth performance, feed conversion ratio (FCR), feed utilization efficiency (FUE), and survival rate. Data were analyzed using ANOVA followed by Duncan’s multiple range test. The results showed that adding 12% K. alvarezii flour fermented with EM4 significantly improved feed protein content (50.1%) and total amino acid levels (35.71%). A significant interaction between fermenter type and concentration was observed for fish growth, while FCR and FUE were significantly influenced by fermenter type alone. The best treatment was observed in fish feed with diets containing 12% EM4 fermented K. alvarezii flour.