A 16-day rearing trial was performed to investigate the influence of two supplemental levels (5% and 10%) of six dietary fat sources (linseed oil, peanut oil, coconut oil, soybean oil, lard oil and fish oil) on the growth, development and nutrient composition of black solider fly larvae. Our results demonstrated that the pre-pupa rate of larvae was linearly influenced by dietary C18:0, C18:3n-3 and C18:2n-6 content (pre-pupa rate = 0.927 × C18:0 content + 0.301 × C18:3n-3 content-0.258 × C18:2n-6 content p < 0.001)), while final body weight was linearly influenced by that of C16:0 (final body weight = 0.758 × C16:0 content, p = 0.004). Larval nutrient composition was significantly affected by dietary fat sources and levels, with crude protein, fat and ash content of larvae varying between 52.0 and 57.5, 15.0 and 23.8, and 5.6 and 7.2% dry matter. A higher level of C12:0 (17.4–28.5%), C14:0 (3.9–8.0%) and C16:1n-9 (1.3–4.3%) was determined in larvae fed the diets containing little of them. In comparison, C16:0, C18:1n-9, C18:2n-6 and C18:3n-3 proportions in larvae were linearly related with those in diets, with the slope of the linear equations varying from 0.39 to 0.60. It can be concluded that sufficient C16:0, C18:0 and C18:3n-3 supply is beneficial for larvae growth. Larvae could produce and retain C12:0, C14:0, and C16:1n-9 in vivo, but C16:0, C18:1n-9, C18:2n-6 and C18:3n-3 could only be partly incorporated from diets and the process may be enhanced by a higher amount of dietary fat. Based on the above observation, an accurately calculated amount of black soldier fly larvae could be formulated into aquafeed as the main source of saturated fatty acids and partial source of mono-unsaturated and poly-unsaturated fatty acids to save fish oil.

A 12-week experiment was conducted to evaluate the influences of thiamine on growth performance and intestinal mitochondrial biogenesis and function of M. amblycephala fed a high-carbohydrate (HC) diet. Fish (24.73 ± 0.45 g) were randomly assigned one of four diets; two carbohydrate levels (30 and 45%) and two thiamine levels (0 and 1.5 mg kg-1). HC diets significantly decreased DGC, GRMBW, FIMBW, intestinal activities of amylase, lipase, Na+, K+-ATPase, CK, complex I, III and IV, intestinal microvilli length, number of mitochondrial per field, ΔΨm, the P-AMPK/T-AMPK ratio, PGC-1β protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1β, TFAM, Opa-1, ND-1 and COX-1 and 2, while the opposite was true for ATP, AMP and ROS, and the transcriptions of Drp-1, Fis-1 and Mff. Dietary thiamine concentrations significantly increased DGC, GRMBW, intestinal activities of amylase, Na+, K+-ATPase, CK, complex I and IV, intestinal microvilli length, number of mitochondrial per field, ΔΨm, the P-AMPK/T-AMPK ratio, PGC-1β protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1β, Opa-1, ND-1, COX-1 and 2, SGLT-1 and GLUT-2. Furthermore, a significant interaction between dietary carbohydrate and thiamine was observed in DGC, GRMBW, intestinal activities of amylase, CK, complex I and IV, ΔΨm, the AMP/ATP ratio, the P-AMPK/T-AMPK ratio, PGC-1β protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1β, Opa-1, COX-1 and 2, SGLT-1 and GLUT-2. Overall, thiamine supplementation improved growth performance, and intestinal mitochondrial biogenesis and function of M. amblycephala fed HC diets.

This study evaluated the effect of Lentinus edodes fermentation (LEF) on digestive enzyme activity, antioxidant capacity and morphology of the liver and intestine in largemouth bass (Micropterus salmoides) fed high plant protein diets (HPPD). LEF was supplemented in HPPD with 0 g kg−1 (LEF0), 10 g kg−1 (LEF1), 20 g kg−1 (LEF2), 30 g kg−1 (LEF3), 40 g kg−1 (LEF4), 50 g kg−1 (LEF5), respectively, and then the six diets were fed to largemouth bass with a body weight of 28.8 ± 0.05 g for eight weeks. Juvenile fish were randomized into 6 groups and each group had 4 replicates with 40 fish. Dietary LEF supplementation alleviated the liver inflammatory reaction of largemouth bass caused by HPPD and improved liver morphology. Goblet cells multiplied and the gut muscle layer thickened after LEF supplementation. The LEF significantly increased amylase activity in the liver and intestine of largemouth bass in individual experimental groups. The LEF could increase the activity of catalase in the liver and intestine of largemouth bass (p < 0.05). The content of malondialdehyde was significantly lower than that in the control group (p < 0.05). Dietary LEF supplementation had no significant effect on the intestinal flora of largemouth bass. These findings imply that LEF supplementation can reduce liver inflammation, enhance intestinal tissue morphology, and eventually benefit largemouth bass health.