Is Maize Gluten a Sustainable and Effective Aquafeed Protein?

ABSTRACT Maize gluten meal (MGM) can be considered unbalanced in its amino acid profile when used as a fishmeal replacement in aquafeeds. To address this, the present study evaluated MGM as the primary dietary protein source at two inclusion levels in common carp ( Cyprinus carpio ), with supplementation of crystalline essential amino acids (EAA). Six iso‐nitrogenous (40% crude protein) and iso‐lipidic (12% crude lipid) diets were formulated based on a basal control diet (Diet1: CTRL). One of these diets was produced in which MGM replaced dietary crude protein at 50% (Diet 2: MGM‐50) without EAA supplementation. The third diet was formulated at 75% MGM substitution level and supplemented with l ‐methionine and l ‐threonine to meet known requirements (Diet 3: MGM‐75). Compounding on the l ‐methionine and l ‐threonine inclusion, supplemental l ‐lysine was included to produce the fourth diet (Diet 4: MGM‐75+lys.r). The final two diets contained the same multiple EAA supplementation as the previous diet, but with lysine content doubled to meet the CTRL level (Diet 5: MGM‐75+lys.RD) and with additional l ‐arginine to counteract potential lysine‐arginine interactions (Diet 6: MGM‐75+lys.RD arg.). Post‐feeding trial of nine weeks showed that the optimal growth performance, in terms of weight gain, feed utilisation efficiency and apparent net protein utilisation, was achieved in the CTRL group (SGR 3.01% day −1 and weight gain of 178.17%), followed by MGM‐50 (SGR of 2.65% day −1 ; weight gain of 166.5%). Among all EAAs dietary supplementation, the addition of all EAAs produced the highest weight gain (134.82%, MGM‐75+lys.RD arg.). Using life cycle assessment techniques, the feed formulation with the lowest impact was MGM‐75. Although fish performance was assessed, MGM‐75 had the highest environmental burden due to its high food conversion ratio, resulting in CTRL and MGM‐75+lys.RD.arg diets having the lowest environmental impact.