Dietary exposure to melamine and cyanuric acid induced growth reduction, oxidative stress and pathological changes of hepatopancreas in Pacific white shrimp

Abstract

This study examined the effects of dietary melamine (MEL) and cyanuric acid (CYA) singly and in combination on growth, nutrient utilization, immunological responses, oxidative stress, and histological changes in Pacific white shrimp. Seven experimental isonitrogenous (35%) and isolipidic (8%) diets were formulated, namely diet 1 (a control diet without MEL and CYA); diets 2–5 (with MEL and CYA at 2.5 + 2.5, 5 + 5, 7.5 + 7.5 and 10 + 10 g kg−1 diet); diet 6 (with only MEL at 10 g kg−1 diet) and diet 7 (with CYA alone at 10 g kg−1 diet). The shrimp with initial body weight 2.37 ± 0.02 g were fed with these diets for 10 weeks. The results indicate that all the diets with MEL and CYA singly or in combination had adverse effects on growth and nutrient utilization relative to the control diet (<em>p</em> < 0.05). Total protease and trypsin activities were significantly lowered by all diets containing MEL (<em>p</em> < 0.05). Haemolymph parameters, including total hemocyte count, phenoloxidase (PO) activity, respiratory burst, and lysozyme activity, were significantly decreased (<em>p</em> < 0.05) in shrimp receiving MEL alone (10 g kg−1 diet) and at high combination dosages (10 + 10 g kg−1 diet). Moreover, MEL and CYA induced oxidative stress, damaged hepatopancreas, decreased antioxidant responses, increased lipid peroxidation, and caused abnormality of hepatocytes.