Elevated levels of dietary ascorbic acid increase immune responses in channel catfish

Area of Science:

• Aquaculture
• Fish immunology
• Nutritional science

Background:

• Ascorbic acid (vitamin C) is essential for fish health and immune function.
• Channel catfish require dietary ascorbic acid to prevent scurvy and maintain health.
• Understanding ascorbic acid's role in immunity is vital for aquaculture disease management.

Purpose of the Study:

• To investigate the effects of dietary ascorbic acid levels on channel catfish immune responses.
• To determine the optimal dietary ascorbic acid dose for enhancing disease resistance against Edwardsiella ictaluri.
• To assess the impact of ascorbic acid on specific immune parameters like antibody production and phagocytosis.

Main Methods:

• Channel catfish fingerlings were fed purified diets with varying ascorbic acid concentrations (0-3000 mg/kg).
• Fish were challenged with Edwardsiella ictaluri to assess mortality rates and disease resistance.
• Immune parameters including antibody production, complement activity, and phagocytic activity were measured.

Main Results:

• Mortality rates due to Edwardsiella ictaluri infection decreased significantly with increasing dietary ascorbic acid.
• Fish fed diets deficient in ascorbic acid showed impaired antibody response, complement activity, and phagocytosis.
• A high dose of 3000 mg/kg ascorbic acid significantly enhanced antibody production and complement activity.

Conclusions:

• Dietary ascorbic acid supplementation is crucial for improving channel catfish immunity and resistance to bacterial infections.
• Adequate ascorbic acid levels enhance key immune functions, reducing disease-related mortality in aquaculture.
• Specific immune parameters are dose-dependently affected by ascorbic acid, with high doses offering superior immune enhancement.