Inositol Inclusion Affects Growth, Body Composition, Antioxidant Performance, and Lipid Metabolism of Largemouth Bass (Micropterus salmoides).

The present study explored the effects of inositol on growth performance, body composition, antioxidant performance, and lipid metabolism of largemouth bass (Micropterus salmoides). Six isonitrogenous and isolipidic diets containing 0 mg/kg (G1, control), 125 mg/kg (G2), 250 mg/kg (G3), 375 mg/kg (G4), 500 mg/kg (G5), and 625 mg/kg (G6) inositol were prepared and fed to cultured fish (initial weight: 110 ± 1 g) for 8 weeks in recirculating the aquaculture systems. The results indicated that compared with G1 group, the weight gain rate (WGR), specific growth rate (SGR), and feed efficiency rate (FER) in the G3 group were significantly higher. The crude lipid content of the whole fish and the liver of cultured fish was significantly reduced with increasing dietary inositol inclusion. However, no significant effects on moisture, crude protein, and ash contents of fish were observed among the different groups. Dietary inositol supplementation significantly increased muscular crude protein. However, muscular total lipid contents were decreased when the inclusion level was higher than 250 mg/kg (G3-G6 groups). As dietary inositol supplemental level increased, serum triglyceride (TG), and cholesterol (TC) contents showed an increasing trend and reached the maximum value in the G3 group. Additionally, serum low-density lipoprotein cholesterol (LDL-C) in G2, G3, G4, and G5 groups was significantly upregulated by increasing inositol. While, there was no significant change in serum high-density lipoprotein cholesterol (HDL-C) among the treatments. Inositol inclusion also significantly reduced the serum alkaline phosphatase (AKP), glutamic-pyruvic transaminase (ALT), and glutamic-oxaloacetic transaminase (AST) activities as well as serum malondialdehyde (MDA) content but significantly increased serum catalase (CAT), superoxide dismutase (SOD) activities, and total antioxidant capacity (T-AOC). Compared with the control group, the activities of hepatic total lipase (TL) and lipoprotein lipase (LPL) were significantly elevated in the G3, G4, and G5 groups. Above all, dietary inositol supplementation could improve growth performance and antioxidant capacity, and reduce the liver fat content of largemouth bass, and the optimal supplementation level of inositol in feed is estimated to be 250.31-267.27 mg/kg.

Effects of Dietary Phospholipids on Growth Performance, Digestive Enzymes Activity and Intestinal Health of Largemouth Bass (Micropterus salmoides) Larvae.

While the beneficial roles of dietary phospholipids on health status and overall performances of fish larvae have been well demonstrated, the underlying mechanisms remain unclear. To address this gap, the present study was conducted to investigate the effects of dietary phospholipids on growth performance, intestinal development, immune response and microbiota of larval largemouth bass (Micropterus salmoides). Five isonitrogenous and isolipidic micro-diets were formulated to contain graded inclusion levels of phospholipids (1.69, 3.11, 5.23, 7.43 and 9.29%). Results showed that the supplementation of dietary phospholipids linearly improved the growth performance of largemouth bass larvae. The inclusion of dietary phospholipids increased the activity of digestive enzymes, such as lipase, trypsin and alkaline phosphatase, and promoted the expression of tight junction proteins including ZO-1, claudin-4 and claudin-5. Additionally, dietary phospholipids inclusion alleviated the accumulation of intestinal triacylglycerols, and further elevated the activity of lysozyme. Dietary phospholipids inhibited the transcription of some pro-inflammatory cytokines, including il-1ß, and tnf-α, but promoted the expression of anti-inflammatory cytokines tgf-ß, with these modifications being suggested to be mediated by the p38MAPK/Nf-κB pathway. The analysis of bacterial 16S rRNA V3-4 region indicated that the intestinal microbiota profile was significantly altered at the genus level with dietary phospholipids inclusion, including a decreased richness of pathogenic bacteria genera Klebsiella in larval intestine. In summary, it was showed that largemouth bass larvae have a specific requirement for dietary phospholipids, and this study provided novel insights on how dietary phospholipids supplementation contributes to improving the growth performance, digestive tract development and intestinal health.

Antioxidant defenses and non-specific immunity at enzymatic and transcriptional levels in response to dietary carbohydrate in a typical carnivorous fish, hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂).

The present study was conducted to explore the influence of dietary carbohydrate on antioxidant capacity and non-specific immunity of hybrid grouper, which would contribute to determine the tolerable dietary carbohydrate content. Seven diets with grade levels of carbohydrate (5.27, 8.95, 11.49, 14.37, 17.78, 20.82 and 23.65%) were fed to triplicate groups of fish for 10 weeks. Results showed that the inclusion of carbohydrate above 11.49% produced significant increased content of hydrogen peroxide (H2O2) in liver and malondialdehyde (MDA) in both serum and liver. The specific activity of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (Gpx) and total antioxidative capacity (T-AOC) were significantly elevated with the increase of dietary carbohydrate from 8.95 to 23.65%, which may be associated with the reduced hepatic soluble protein content. However, opposite variation was observed in the expression of antioxidant related genes (SOD1 and Gpx), which was partly caused by the activation of NF-E2-related factor 2 (Nrf2) and inhibition of Kelch-like-ECH-associated protein 1 (Keap1) at the transcriptional level. The immunoglobulin M (lgM) content and activity of lysozyme and CCP in serum significantly depressed when dietary carbohydrate was above 11.49%. The expression of pro-inflammatory cytokines (TNF-α, IL-1ß and IL-8) was significantly increased with the increase of dietary carbohydrate from 5.27 to 8.95% and thereafter significantly reduced, which was consistent with the changed expression of toll-like receptor 2 (TLR2) and nuclear factor κΒ (NF-κΒ). In above, high dietary carbohydrate significantly impaired the antioxidant capacity and reduced the non-specific immunity of hybrid grouper, and the tolerable dietary carbohydrate content should not exceed 11.49%.