Affiliation:
1. School of Fisheries, Xinyang Agriculture and Forestry University, Xinyang 464000, China
2. Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, China
3. Shenzhen Base of South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shenzhen 518121, China
4. Tropical Fisheries Research and Development Center, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Sanya 572018, China
Abstract
Seven graded levels of sodium propionate (SP) diets with 0 (SP1), 0.2% (SP2), 0.4% (SP3), 0.6% (SP4), 0.8% (SP5), 1.0% (SP6), and 1.2% (SP7) were prepared to feed Trachinotus ovatus (initial body weight: 8.64 ± 0.08 g) for 56 days. The results showed that increasing dietary SP levels quadratically increased significantly final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) of T. ovatus but linearly and quadratically decreased significantly viscerosomatic index (VSI) and hepatosomatic index (HSI) of T. ovatus (). In the SP4 treatment, FBW, WGR, and SGR presented the highest values. Both positive linear and quadratic trends were detected between crude lipid content of whole fish, adhesiveness of dorsal muscle, white blood cell (WBC), red blood cell (RBC), hemoglobin (HGB), blood performance, high-density lipoprotein cholesterol (HDL-c), intestinal villus height, and dietary SP level, while negative linear and quadratic trends were found between firmness of dorsal muscle, triglyceride (TG), glucose (GLU), and dietary SP level (). The increasing SP led to quadratic increases in lymphocyte (Lym), complement 3 (C3), chymotrypsin, villus number, and muscle layer thickness, and a quadratic decrease in hepatic malondialdehyde (MDA). A significant negative linear trend was found between the content of glutamic-pyruvic transaminase (GPT) and dietary SP level, while significant positive linear trends were presented between C4, immunoglobulin M (IgM), α-amylase and dietary SP level (). The increasing SP resulted in linear and quadratic increases in superoxide dismutase (SOD), total antioxidant capacity (T-AOC) of livers and C3, C4, IgM of head kidney (). The expression levels of tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8) were linearly and quadratically decreased, while the mRNA levels of growth factor beta (TGF-β) were linearly and quadratically increased with the increasing SP level (). In conclusion, SP could be considered as a beneficial feed additive for enhancing growth and immunity of fish. And dietary SP level at 0.6% is optimal for the growth of Trachinotus ovatus based on a quadratic regression model of WGR.
Funder
Guangdong Provincial Special Fund for Modern Agriculture Industry Technology Innovation Teams