Dietary Supplementation of Isochrysis galbana Biomass in Trachinotus Blochii: Effects on Growth, Feed Utilisation and Physiological Responses

Abstract

This study examined the use of dried Isochrysis galbana biomass as a functional feed ingredient for Trachinotus blochii. T.blochii with an initial body weight of 42 ± 2 g were acclimatised for 14 days before being fed experimental diets containing control  (T0), 0.5% (T1), 1.0% (T2) or 1.5% (T3) dried algal biomass for 60 days. Each treatment was tested in triplicate, with 10 fish per tank. The diets contained 38.87–39.95% crude protein and 6.14–6.51% crude lipid. Growth differences among treatments were not statistically significant. However, the reported feed conversion ratio (FCR) decreased from 1.77 in the control to 1.66 in T2 and T3, while feed conversion efficiency (FCE) reached 0.605 in T3. Whole-body protein and lipid contents varied among treatments; the highest reported protein content was 72.30% in T1 and the highest lipid content was 15.68% in T2. Significant dietary effects were reported for serum cholesterol, albumin, total protein and triglycerides. In T2, cholesterol and total protein reached 75.67 mg dL⁻¹ and 5.38 g dL⁻¹, respectively. Liver and intestinal amylase activities were also highest in T2, at 45.89 and 75.88 U mg⁻¹ protein, respectively, with significant differences reported among treatments. Superoxide dismutase (SOD) and catalase (CAT) activities showed numerical increases, while the manuscript contains conflicting statements about flesh-colour responses that require confirmation. Overall, the results suggest that dried I. galbana biomass may influence selected aspects of feed utilisation, digestive activity and physiological responses. T2 (1.0% inclusion) showed comparatively high values for several measured parameters, but the inconsistencies identified in the manuscript should be resolved before firm conclusions are drawn.