A team of researchers, together with BioMar, evaluated the optimal dietary micronutrient supplementation of plant-based diets for juvenile European seabass (Dicentrarchus labrax).
A 90-day feeding trial was performed where fish were fed a high fishmeal-based diet (62% fishmeal; positive control) or a low fishmeal diet (12.5% fishmeal and krill meal) and supplemented with increasing levels of a micronutrient mixture (Nutrient Package, NP) consisting of vitamins, minerals and other micronutrients. The supplementation levels ranged from 0% (no supplementation, negative control) to 400%, where 100% supplementation level corresponded to the required levels recommended for other fish species.
Researchers found that fish growth and feed performance were significantly impaired at levels NP0 and NP25 compared to the fishmeal control. Body iron and zinc concentrations were positively affected by the graded levels of the NP, while manganese and selenium concentrations remained stable. Researchers said that growth parameters were particularly correlated to body iron and zinc, while immune parameters were mainly correlated to body zinc.
Significant immunosuppression was evidenced (concerning the respiratory burst activity) when low fishmeal diets were not supplemented with NP. High inclusion levels of the NP showed a negative impact on lysozyme activity. At identical NP supplementation level (50%), fish fed low and high fishmeal diets showed similar growth and innate immunity suggesting that long-term feeding with plant-based diets does not significantly affect the fish when adequate minerals and vitamin supplementation is provided.
The inclusion of the NP between 260% and 300% improves growth and immune parameters of fish fed low-fishmeal diets as well as zinc body incorporation. “The present study suggests the positive impact of NP supplementation of plant-based diets on both fish growth and health but future NP could include less manganese and more iron, closer to levels obtained in fish fed fishmeal (245 mg kg−1), and zinc at 122 mg kg−1,” researchers said.
Check out the study here.
