Iron is a vital trace mineral involved in many biochemical processes in fish, including Atlantic salmon. The dietary requirement for iron in Atlantic salmon ranges from 60 to 160 mg/kg. However, these requirements were established using purified diets with highly bioavailable iron forms and may not reflect the needs in practical diets where interactions with antinutrients such as phytate can affect iron bioavailability.
Joana Silva and her team conducted a study to evaluate the impact of iron supplementation on post-smolt Atlantic salmon’s performance, pigmentation, health, and oxidative status when fed practical diets. The study was conducted over ten weeks at BioMar’s trial facility, ATC Patagonia. Fish were divided into duplicate groups of 100 and allocated to 14 tanks. Seven low fish meal diets supplemented with an organic Fe-AA complex at graded levels (208 – 443 mg/kg total Fe) were tested.
The results showed that iron supplementation through an organic Fe-AA complex did not significantly affect the growth performance of post-smolt Atlantic salmon. “Hemoglobin (Hb) concentrations were significantly higher in groups fed with diets containing higher levels of iron (D4, D5, D7) compared to the basal diet without iron supplementation (D1)” said Silva (p<0.001). Lactate dehydrogenase (LDH) levels were also lower in the highest iron group (D7), indicating better physiological condition under chronic stress (p<0.05).
No significant differences were found in the oxidative status of key nutrients among different diets, indicating that the organic Fe-AA complex did not promote oxidation even at high supplementation levels. Significant improvements in fish pigmentation were observed with increasing iron supplementation. Fillets from fish fed the highest iron diet exhibited significantly higher redness and yellowness compared to the basal diet group.
These findings suggest that supplementing iron through an organic amino acid complex does not compromise feed’s oxidative stability and improves hemoglobin levels and reduces LDH in plasma, indicating improved health and better capacity to handle stress in post-smolt Atlantic salmon. Iron supplementation up to 230 mg/kg through an organic Fe-AA complex can improve health status and pigmentation without negatively impacting performance.