Comparative evaluation of two shrimp head meals as dietary ingredients for Nile tilapia Oreochromis niloticus: Effects on nutrient digestibility, amino acid chemical score, growth performance, digestive enzyme activity and antioxidant parameters

The digestibility and enzymatic and antioxidant effects of shrimp head meal (Penaeus vannamei) as a protein source in the diet of Nile tilapia (Oreochromis niloticus) were evaluated. Two shrimp meals were tested: whole shrimp meal (WSM) and low-lipid shrimp meal (LLSM). Dietary levels of 20 % and 30 % of shrimp meal replaced 80 % and 70 % of the reference diet, respectively. The 60-day experiment was conducted in a modified Guelph system, with nine feeding tanks and nine fecal collection units, each containing 10 fish (61.85 ± 10.06 g). WSM and LLSM supported high digestibility of dry matter, protein, energy, and minerals, with values often exceeding 90 % at 20 % inclusion, except for chitin. Growth performance indicators (weight gain, feed conversion ratio, protein efficiency ratio, and survival) were consistently improved in shrimp-meal diets at both inclusion levels compared with the reference diet, confirming the biological relevance of digestibility results. Essential and non-essential amino acids were highly digestible, with no limiting amino acids, and the chemical score and indispensable amino acid index of both WSM and LLSM exceeded those of protein sources conventionally used in aquafeeds. Inclusion of 20 % and 30 % significantly increased digestive enzyme activities (alkaline protease, trypsin, chymotrypsin, lipase, and amylase), while hepatic antioxidant capacity was enhanced through catalase and reduced glutathione activities, without changes in malondialdehyde levels. Overall, shrimp head meals represent high-quality, bioavailable protein sources for Nile tilapia, contributing simultaneously to improved growth performance and to circular economy strategies through the valorization of shrimp industry by-products.