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

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.

Iron supplementation in the diets of hybrid catfish (Ictalurus punctatus × I. furcatus) juveniles affected haematocrit levels and potentially decreased disease resistance to Edwardsiella ictaluri

“…In contrast to the present study, alterations in intestinal architecture and histological scores were previously documented in channel catfish fed diets supplemented with iron, whether in the form of ferrous sulphate or methionine chelates (Buyinza et al., 2023). In addition, also contrasting with the present study, it has been observed necrosis, inflammation, lipidosis, and hyperemia on the hepatic histology in channel catfish and goldfish fed iron supplemented diets (Akbary & Jahanbakhshi, 2019; Buyinza et al., 2023).…”

“…For teleost fish, it is postulated that dietary iron is likely either stored in the liver or utilized during erythropoiesis, as suggested previously (Bury et al., 2012). This hypothesis aligns with observations made in channel and yellow catfish ( Pelteobagrus fulvidraco ), where a linear increase in hepatic iron concentration was observed when fish were offered diets containing graded levels of iron supplementation (Buyinza et al., 2023; Luo et al., 2017).…”

“…Similarly, growth performance was also promoted by dietary ferrous sulphate supplementation at 300–600 mg/kg in plant‐based diets for rainbow trout (Evliyaoğlu et al., 2022). Finally, in line the current study, no differences in growth performance were reported in channel catfish fed diets supplemented with different concentrations of iron sulphate (Barros et al., 2000, 2002) or iron‐methionine (Buyinza et al., 2023; Lim et al., 1996).…”

“…Iron supplementation in catfish diets has been investigated over the decades; and research has focused to potentially prevent anaemia (Buyinza et al., 2023; Camus et al., 2014), addressing toxicosis resulting from cottonseed meal gossypol (Barros et al., 2000, 2002), and evaluating the availability of this mineral from organic, inorganic, and nanoscale sources (Buyinza et al., 2023; Lim & Klesius, 1997; Lim et al., 1996; Sealey et al., 1997; Siqwepu et al., 2020; Uzo‐God et al., 2019). In addition, studies also shed light whether the disease resistance of catfish against E. ictaluri could be compromised when feeding iron supplemented diets (Barros et al., 2002; Sealey et al., 1997).…”

“…There is increased incidence of this disease in late spring and early summer, typically manifesting as reduced feeding activity, accompanied by schooling of the resident fish behind aerators consistent with oxygen stress and hypoxia (Camus et al., 2014). Anecdotal reports from the U.S. catfish suggest fortifying feed with inorganic iron beyond the established requirement may reduce incidence of anaemia in the spring and fall (Buyinza et al., 2023). Nevertheless, the practical implementation of this concept by feed mills has faced challenges related to logistics and storage, leading to diets being consistently supplemented with approximately 500–700 mg/kg of iron year‐round.…”