Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 1996
Publication Date: N/A
Interpretive Summary: Iron is a necessary nutrient for virtually all living organisms. It is involved in many types of organic reactions and is essential for oxygen movement and activity of several enzymes. In fish, feed is the major source of iron. Previous work with the iron requirement of channel catfish has dealt with establishing dietary minimums required for normal growth and hematological values. Iron is necessary for normal immune function in mammals. The effect of iron on immune function and disease resistance in channel catfish has not been investigated. In recent studies, minerals chelated to amino acids have been shown to increase immune function in fish. The purpose of our study was to determine the level of iron sulfate necessary for optimum immune function and to determine if chelation of iron to the amino acid methionine lowered this level. Results of the study showed that optimum iron level and source was dependent on the immune parameter being examined. In addition, iron deficiency increased mortality due to enteric septicemia.
Technical Abstract: Channel catfish (Ictalurus punctatus) fingerlings were fed purified diets supplemented with iron at levels of 0, 20, 60, and 180 mg/kg from iron sulfate (FeS) or 5, 10, 20, 60, and 180 mg/kg from iron methionine (FeM) in triplicate tanks for 8 weeks. Representative fish from each dietary treatment were challenged by bacterial immersion with virulent Edwardsiella ictaluri and mortality due to enteric septicemia was recorded. Other fish were immunized with 0.2 mL formalin-killed E. ictaluri and boostered 21d post immunization. Antibody response was determined by FAST-ELISA. Chemiluminescent, chemotaxis, intracellular superoxide anion production and bactericidal assays were performed using peritoneal macrophages. The dietary iron level for optimum antibody production was 180 mg/kg diet provided as FeS and 60 mg/kg as FeM. For chemiluminescence and chemotactic migration by macrophages, FeS and FeM were equally effective and a level of 60 mg Fe/kg was found to be optimum. Macrophages from fish fed FeM had greater superoxide anion production than macrophages from fish fed the 20 mg/kg FeS. Macrophage bactericidal activity was highest in fish fed the 20 mg/kg FeS. A deficiency of dietary iron was found to increase mortality of channel catfish due to enteric septicemia.