Utilization of a commercial probiotic, effective microorganisms, in diet fermentation for rabbitfish grow-out

Rabbitfish ( Siganus guttatus ) is a herbivorous fish that can utilize a plant-based diet better than omnivore and carnivorous fish. However, the quality of the plant-based diet still needs to be improved so that the rabbitfish can grow faster with better feed efficiency. One effort that is thought to be done to improve the quality of diet is fermentation. Therefore, this study aims to evaluate the use of effective commercial microorganisms (EM-4) probiotics in the fermented plant-based diet on the growth performance of rabbitfish. The treatments tested were fermentation of ingredient plant-based diet using EM-4 at different doses namely: F10 (10 mL), F20 (20 mL), F30 (30 mL), F40 (40 mL) per kilogram substrate and WF (unfermented diet). The test diets were given to the rabbitfish juvenile that was cultured in floating net cages in the sea. The initial weight of the test fish is around 48 g, maintained in 15 units of 1x1x1.5 m cage; they fed with satiation in the morning, afternoon, and evening for four months. The results showed that the fermented diet with EM-4 at all doses tends to increase in the content of free fatty acid, total n-3, total n-6, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) compared to these fatty acids contents in the unfermented diet. The specific growth rate, weight gain, feed efficiency, and protein efficiency ratio was not significantly different (P>0.05) between the treatments. Feed intake was significantly different (P<0.05) between treatment, and it was highest in fish fed the unfermented diet compared to fish fed the fermented diet. Fermentation of the test diets with EM-4 has not been able to improve feed utilization and growth of rabbitfish.