Evaluation of Dietary Vitamin C Supplementation as a Growth-Promoting Strategy in <i>Labeo rohita</i> Fingerlings

Vitamin C (ascorbic acid) is an essential water-soluble micronutrient required for normal growth, collagen synthesis, antioxidant defense, and immune function in fish. Although its beneficial effects have been reported in several aquaculture species, the optimal dietary requirement for Labeo rohita (rohu) fingerlings remains inadequately defined. The present study evaluated the effects of graded dietary vitamin C supplementation on the growth performance and feed utilization of L. rohita fingerlings under controlled culture conditions. A total of 72 healthy fingerlings (initial body weight 2.62 ± 0.30 g) were randomly allocated to four dietary treatments with three replicates per treatment. Fish were fed isonitrogenous diets containing 0 (control), 50, 70, and 90 mg kg⁻¹ vitamin C for 10 weeks. Growth performance was assessed using final body weight, length gain, weight gain, specific growth rate (SGR), and feed conversion ratio (FCR). Water quality parameters, including temperature, dissolved oxygen, pH, hardness, and alkalinity, were monitored throughout the experiment to ensure suitable rearing conditions. Data were analyzed using one-way ANOVA followed by Duncan's Multiple Range Test. Dietary vitamin C supplementation significantly improved growth performance compared with the control (p < 0.05). Fish receiving 90 mg kg⁻¹ vitamin C exhibited the highest final length (9.15 ± 0.01 cm), greatest weight gain (3.61 ± 0.02 g), and highest SGR (0.994 ± 0.04%), while achieving the lowest FCR (10.73 ± 0.06), indicating superior feed utilization efficiency. Growth responses increased progressively with increasing dietary vitamin C levels, whereas water quality parameters remained within acceptable ranges and did not differ significantly among treatments. Dietary supplementation with 90 mg kg⁻¹ vitamin C effectively enhanced growth performance and feed efficiency in L. rohita fingerlings. These findings suggest that vitamin C is an economical and practical nutritional strategy for improving rohu production and provide valuable information for optimizing feed formulations to support sustainable freshwater aquaculture.