Iron Methionine and Iron Sulfate as Sources of Dietary Iron for Channel Catfish Ictalurus punctatus

The dietary iron requirement for normal growth and optimum hematological values and bioavailability was determined for channel catfish Ictalurus punctatus fingerlings using eggwhite based diets supplemented with 0,5,10,20,60, and 180-mg ironkg from iron methionine or 20, 60, and 180-mg ironkg from iron sulfate. The basal diet which contained 9.2-mg ironkg, 34% crude protein and 3.1 kcal of digestible energylg was fed to channel catfish fingerlings (8.5 g) in triplicate flow-through aquariums to satiation twice daily for 8 wk. Fish fed the basal diet without iron supplementation exhibited poor growth throughout the 8-wk period. Fish fed iron-supplemented diets did not differ with regard to final weight gain. Survival, feed conversion, total blood cell count, mean corpuscular hemoglobin concentration, serum iron, total iron binding capacity, and transferrin saturation were not significantly affected by dietary iron level. Hemoglobin, hematocrit, mean corpuscular hemoglobin, and mean corpuscular volume were significantly lower in fish fed the basal diet. These values were also consistently lower for fish fed diets with 5 and 10-mg ironkg from iron methionine. However, differences were not always significant. Results of this study indicate that supplementation of 5-mg iron from iron methionine was sufficient for growth. However, a supplemental iron level of 20-mgkg diet or a total iron level of 3O-mgkg of diet appeared to be needed for optimum hematological values. Iron methionine and iron sulfate were equally effective in preventing anemia in channel catfish. Iron is an essential element in all higher animals including fish because of its importance in cellular respiration and mitosis (Robbins et al. 1972). Although fish can absorb soluble iron across the gill membrane and intestinal mucosa (Roedar and Roedar 1968), feed is considered as the major source of iron for fish due to low concentrations of soluble iron in natural waters (NRC 1993). Dietary iron requirements have been determined for several species of fish including red sea bream Chrysophrys major (Sakamoto and Yone 1976, 1978a), yellowtail Seriolu quinquerudiutu (Ikeda et al. 1973), common carp Cyprinus curpio (Sakamoto and Yone 1978b), eel Anquillu juponicu (Nose and Arai 1979), Atlantic salmon Sulmo sulur (La11 and Hines 1987), and channel catfish Ictalurus punctatus (Gatlin and Wilson 1986). I Corresponding author. The total dietary iron requirement for channel catfish fingerlings was determined by Gatlin and Wilson (1986) to be not more than 30 mgkg diet. Fingerlings fed irondeficient diets had decreased weight gain, feed efficiency, hematocrit, hemoglobin, transfemn saturation and erythrocyte values. This requirement was determined with purified diets utilizing iron sulfate as the dietary iron source. Studies with mammals have shown that chelation of minerals to amino acids may increase their absorption rate in the intestine (Ashmead 1992). More recently, Paripatananont and Love11 (1 995) reported that using zinc methionine as the dietary zinc source reduced the dietary zinc requirement of channel catfish in both purified and practical diets as compared to diets containing zinc sulfate. No studies have been conducted on the dietary iron requirement of channel catfish using a chelated source of iron. The objective of this study was to deter0 Copyright by the World Aquaculture Society 1996