Elevated concentrations of organic and inorganic forms of iron in plant-based diets for channel catfish prevent anemia but damage liver and intestine, respectively, without impacting growth performance

Abstract

Abstract We compared the effects of using inorganic and organic forms of iron in plant-based diets on catfish performance in a feeding trial with catfish fingerlings (initial weight = 6.1 ± 0.2 g). Five diets supplemented with 0 (basal), 125, 250 mg Fe/kg of either FeSO4 or iron methionine were formulated. Fish weight gain, feed conversion ratio, hepatosomatic index, and survival were similar among diets. Fish plasma and intestine iron concentration was similar among diets. Fish whole-body total lipid, protein, and dry matter were similar among diets. Ash content was higher in fish fed the basal diet than in other diets. Total liver iron concentration was higher in fish fed diets supplemented with 250 mg Fe/kg in both iron forms than other diets. Hematological parameters were similar among diets. Liver necrosis, inflammation, and vacuolization were highest in fish fed the diet supplemented with 250 mg Fe/kg from organic iron, followed by those fed diets with 250 mg Fe/kg from inorganic iron. Inorganic iron-supplemented diets caused more intestinal inflammation characterized by increased inflammatory cells, swelling of the villi, and thicker lamina propria than the organic iron-supplemented diets or the basal diet. Organic iron at 250 mg/kg resulted in a 0.143$/kg increase in feed cost. Latent iron deficiency and initial signs of anemia developed in catfish fed the basal diet. Supplemental iron from either form prevented iron deficiency in fish. Organic iron at 125 mg/kg optimized fish performance at a cost comparable to that of fish fed other diets, but without overt negative effects.