Effects of graded levels of minerals in a multi‐nutrient package on Gilthead sea bream (Sparus aurata) fed a plant‐based diet.

Replacement of fish meal (FM) and oil (FO) by plant sources can alter the feed mineral profile. However, requirements of these nutrients have not been established for gilthead sea bream. The aim of the present study was to obtain information about the adequate levels of some of these minerals (such as Zn, Cu, Mn, Se, Co, Fe and Ca) in diets with low FM and FO levels. Six plant‐based practical diets were supplemented with increasing levels of a multi‐nutrient package for 155 days. Performance parameters, biochemical analyses of whole body, vertebrae, plasma and blood cells; haematocrit; expression of several genes in liver and vertebrae were conducted. Increasing multi‐nutrient package affected fish growth, expression of molecular markers and mineral content in different tissues. A regression method was used to establish a relation between multi‐nutrient package levels and different indicators. However, nutrient interactions made it difficult to obtain clear results and so specific effects of each mineral must be studied in more detail. Mineral supplementation was required for Zn, Cu, Mn, Se and Co, whilst basal levels of Ca were sufficient to cover the optimum levels. On the other hand, there is evidence regarding a possible interaction between Fe and Zn which reduced Fe availability and absorption. [ABSTRACT FROM AUTHOR]