The aim of this study was to investigate the potential effects of monosodium glutamate (MSG), a known flavour enhancer added to many ready‐to‐eat foods, as a feed additive in rainbow trout ( Oncorhynchus mykiss ). Evaluating the effects of MSG on aquatic organisms will fill the knowledge gap in this field by monitoring the haematological indices of O. mykiss with growth parameters and somatic indices, histomap mapping with his...