Effects of dietary zinc on growth performance, digestive enzyme activities, antioxidant status and immune responses of sea cucumber Apostichopus japonicus

Abstract

Abstract This study evaluated the effects of dietary zinc on growth performance, digestive enzyme activities, antioxidant status and immune responses of sea cucumber Apostichopus japonicus. Five experimental diets were formulated with graded levels of zinc (0, 20, 40, 60, and 80 mg/kg, respectively), and the actual dietary zinc values were 31.4, 51.0, 68.2, 91.9, and 110.8 mg/kg diet, respectively. Sea cucumbers were fed with diets for 2 months. The results showed the growth performance, amylase and trypsin activities of sea cucumber increased significantly with zinc supplementation, and the best growth performance and enzyme activities were observed at 40 mg/kg zinc diet. Zinc supplementation significantly increased activities of superoxide dismutase (SOD), catalase (CAT), anti-superoxide anion (ASA) and inhibiting hydroxyl radical (AHR), while significantly reduced the malondialdehyde (MAD) content. Furthermore, the higher Zn supplementation levels resulted in significantly upregulated immune-related genes of hsp90、p105、rel、lsz, suggesting that excessive zinc caused oxidative stress. The broken-line regression analysis of specific growth rate (SGR) indicated dietary zinc requirement in sea cucumber was ~ 66.3 mg/kg diet.