Our study investigated the effects of dietary
zinc (Zn) deficiency on growth performance, intestinal immune and physical barrier functions of young grass carp (Ctenopharyngodon idella). A total of 630 grass carp (244.14 ± 0.40 g) were fed graded levels of
zinc lactate (10.71, 30.21, 49.84, 72.31, 92.56, 110.78 mg Zn/kg diet) and one
zinc sulfate group (56.9 mg Zn/kg diet) for 60 days. At the end of the feeding trial, fish were challenged with Aeromonas hydrophila for 14 days. These results indicated that compared with optimal dietary Zn level, dietary Zn deficiency (10.71 mg/kg diet) decreased the production of antibacterial compounds, up-regulated pro-inflammatory
cytokines related to
nuclear factor kappa B (NF-κB) and down-regulated anti-inflammatory
cytokines related to target of
rapamycin (TOR) in three intestinal segments of young grass carp (P < 0.05), suggesting that dietary Zn deficiency could impair intestinal immune barrier of fish; decreased the activities and
mRNA levels of
antioxidant enzymes related to
NF-E2-related factor 2 (Nrf2), up-regulated the
mRNA levels of
caspase-3, -7, -8, -9 related to p38
mitogen activated
protein (
p38 MAPK) and c-Jun N-terminal
protein kinase (JNK), down-regulated the
mRNA levels of tight junction complexes (TJs) related to
myosin light chain kinase (MLCK) in three intestinal segments of young grass carp (P < 0.05), demonstrating that dietary Zn deficiency could injury intestinal physical barrier of fish. Besides, the Zn requirements (
zinc lactate as Zn source) based on percent
weight gain (PWG), against
enteritis morbidity,
acid phosphatase (ACP) activity in the proximal intestine (PI) and
malondialdehyde (MDA) content in the PI of young grass carp was estimated to be 61.2, 61.4, 69.2 and 69.5 mg/kg diet, respectively. Finally, based on specific growth rate (SGR), feed efficiency (FE) and against
enteritis morbidity of young grass carp, the efficacy of
zinc lactate relative to
zinc sulfate were 132.59%, 135.27% and 154.04%, respectively.