Feeding Mystus gulio Fry With Different Dietary Inclusion of Coccomyxa Sp.: Changes in Nutritional Profile, Pigments and Digestive Enzyme Activities

The aim of this study was to investigate the effects of Coccomyxa sp. on the survival, nutritional profile, pigments and digestive enzyme activities of Mystus gulio. A 75-day feeding trial was performed during which the fish fry were fed with microalgae as a partial replacement for other nutritional components. The fry were fed five different diets: a commercial feed, a control diet without Coccomyxa sp. and three experimental diets incorporating Coccomyxa sp. at varying rates of T1 (5% inclusion), T2 (10% inclusion) and T3 (15% inclusion). Fry (35 per tank) were cultured in triplicate 35 L glass tanks and fed twice a day at 5% of their body weight. The findings showed that among the treatment groups, T3 had the highest survival rate (81% ± 4.36%), followed by T1, T2, control and commercial. Furthermore, T3 had the highest quantities of protein (43.8% ± 6.55% dry weight) and lipids (25.9% ± 0.68% dry weight), whereas T2 had higher amounts of carbohydrate (14.9% ± 1.99% dry weight). Meanwhile, the polyunsaturated fatty acid (PUFA) content varied significantly (p < 0.05) among the treatments, whereas T3 was the highest (41.75 ± 0.12 ppm). Additionally, it was also found that the T3 group exhibited higher carotenoid and astaxanthin content in the fish body. Moreover, the T2 diet resulted in higher levels of amylase (13.7 ± 0.16 U/g) compared to the other diets. Conversely, protease (12.6 ± 0.15 U/g) and lipase (2.20 ± 0.13 U/g) activity were found greater in T3 treatment. These results suggest that microalgae can be used as a viable and alternative feed ingredient in aquaculture diets.