Dietary vitamin C supplementation for mullet Mugil liza broodstock improves the hematological response

Abstract Mugil liza is a coastal euryhaline mullet native to the western Atlantic, recognized for its rapid growth rates, tolerance to wide salinity range (0–35 ppt) and temperature fluctuations, high survival under several farming conditions, and efficient utilization of low-cost plant-based feeds due to its detritivorous and omnivorous feeding habits. These attributes highlight its potential for sustainable aquaculture development. However, information regarding its nutritional requirements is scarce. For several fish species, there is evidence that dietary vitamin C intake can influence the performance of certain immune mechanisms, providing greater resistance to diseases. However, for M. liza , no such information is available yet. Therefore, this study aimed to evaluate the hematological parameters of M. liza fed diets supplemented with varying levels of ascorbic acid (vitamin C), a crucial antioxidant for fish that they cannot synthesize. A total of 144 male broodstock were distributed into six experimental groups in triplicate, receiving diets with 0, 53, 107, 216, 482, and 708 mg kg⁻¹ of vitamin C for 75 days. Blood samples were collected after anesthesia with benzocaine 50 mg L⁻¹ for analyses including erythrocyte count, plasma glucose, plasma total protein, and differential leukocyte counts. Results showed that vitamin C supplementation significantly increased erythrocyte and leukocyte counts, with the highest dose (708 mg kg⁻¹) leading to elevated red blood cell and lymphocyte counts and total protein concentration compared to the control group. Even the lowest dose (53 mg kg⁻¹) improved neutrophil and monocyte production. These findings suggest that vitamin C enhances immune response in M. liza , particularly during the breeding period, potentially increasing the longevity and health of the broodstock, which may also have a positive influence on the quality of the spawn and the health of the resulting larvae.