A 60-day experiment was carried out to investigate dietary starch levels on growth performance, hepatic glucose metabolism and liver histology of largemouth bass, Micropterus salmoides. Fish (initial weight 22.00 ± 0.02 g) were fed five graded levels of dietary corn starch (0, 50, 100, 150 and 200 g/kg). Fish fed low (0 and 50 g/kg) dietary starch showed significantly higher weight gain than other groups (p < .05). Liver lipid and glycogen accumulations were induced when dietary starch higher than 100 g/kg. After 20 days of feeding, hexokinase activity and mRNA expression were decreased in fish fed dietary starch higher than 150 g/kg (p < .05) and the pyruvate kinase showed the opposite tendency. Insulin receptor 1 (irs1), glucagon-like peptide-1 receptor and glucose transport protein 2 (glut2) mRNA expression were decreased with the increasing dietary starch after 10 days of feeding (p < .05). These results indicated gluconeogenesis was depressed and β-oxidation was enhanced in response to high dietary starch, while the glycolysis was inhibited and endocrine system was impaired when fish fed high dietary starch; then, glucose homeostasis was disturbed and finally led to the glucose intolerance of largemouth bass.
The present study investigated the potential mechanisms of astaxanthin in the regulation of gastrointestinal immunity and retinal mitochondrial function of golden pompano ( Trachinotus ovatus ). Triplicate groups of juvenile T. ovatus (mean initial weight: 6.03 ± 0.01 g) were fed one of six diets (D1, D2, D3, D4, D5, and D6) for 8 weeks, with each diet containing various concentrations of astaxanthin (0, 0.0005, 0.001, 0.005, 0.01, or 0.1%, respectively). Growth performance of fish fed the D2–D5 diets was higher than that of fish fed the D1 diet; however, growth performance and survival of fish deteriorated sharply in fish fed the D6 diet. Gut villus in fish fed the D2–D5 diets were significantly longer and wider than that of fish fed the D6 diet. Feeding with D2–D5 diets led to increased abundance of Bacillus , Pseudomonas , Oceanobacillus , Lactococcus , Halomonas , Lactobacillus , and Psychrobacter while abundance of Vibrio and Bacterium decreased. Additionally, feeding with the D6 diet resulted in a sharp decline in Pseudomonas and Lactobacillus abundance and a sharp increase in Vibrio abundance. A low dissolved oxygen environment (DO, 1.08 mg/L) was conducted for 10 h after the rearing trial. No fish mortality was observed for any of the diet treatments. Lysozyme (LZY) activity in fish fed the D6 diet decreased sharply and was significantly lower than that in other groups. ROS production also decreased sharply in fish fed the D6 diet. Moreover, the conjunctiva and sclera in the fish fed the D6 diet were indistinguishable. Suitable dietary astaxanthin supplementation levels (0.005–0.1%) exerting a neuroprotective effect from low dissolved oxygen environments is due to up-regulated expression of anti-apoptotic factors, such as phosphorylated Bcl-2-associated death promoter (pBAD), phosphorylated glycogen synthase kinase-3β (pGSK-3β), Bcl-2 extra large (Bcl-xL), and down-regulated expression of Bcl-2-associated X protein (Bax) pro-apoptotic factor in retinas. Furthermore, suitable dietary astaxanthin levels (0.0005–0.01%) suppressed up-regulation of critical mitochondrial components, such as peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), mitochondrial transcription factor A (TFAM), and mitochondrial DNA (mtDNA), while excessive astaxanthin supplementation produces the opposite effect. In brief, high-dose astaxanthin arouses and aggravates low dissolved oxygen-induced inflammation, oxidative stress, intestinal disorder, retinal apoptosis, and retinal mitochondrial dysfunction in T. ovatus . Second-degree polynomial regression of WG indicated that the optimum dietary astaxanthin for juvenile T. ovatus is 0.049%.
Haematococcus pluvialis can be used as a green additive in aquafeeds due to it contains rich astaxanthin and polyunsaturated fatty acid. In the present study, a newly strain of H. pluvialis GXU-A23 with high concentration of astaxanthin was firstly isolated by a newly culture strategy in our laboratory. In addition, H. pluvialis GXU-A23 was applied in the Litopenaeus vannamei feed for determining whether it has positive effects on the growth performance, antioxidant and anti-inflammatory status, metabolic capacity and mid-intestine morphology of juvenile L. vannamei. Shrimp with 0.63 g approximately initial body weight were fed diets supplemented with/without 50 g/kg H. pluvialis GXU-A23. After 8 weeks feeding intervention, significantly higher growth performance of L. vannamei was obtained in the H. pluvialis GXU-A23 treatment group compared to the control group (p < 0.05). At the same time, L. vannamei fed with H. pluvialis GXU-A23 acquired significantly better antioxidant and anti-inflammatory status than the control group (p < 0.05). In addition, higher RNA expression level of hepatopancreas digestive enzyme, hepatopancreas lipid and glucose metabolic enzymes as well as better mid-intestine morphology were found in the H. pluvialis GXU-A23 treatment group than the control group (p < 0.05). These results indicated that 50 g/kg H. pluvialis GXU-A23 was suitable for the L. vannamei feed, which could improve the growth performance, antioxidant and anti-inflammatory status, metabolic capacity and mid-intestine morphology of juvenile L. vannamei.
The study was conducted to compare and evaluate effects of four different macro-algaes on growth, immune response, and intestinal microbiota of Litopenaeus vannamei. In the rearing trial 1, shrimp were fed five diets containing four sources of macro-algaes for 8 weeks, named D1 (without macro-algae), D2 (Porphyra haitanensis), D3 (Undaria pinnatifida), D4 (Saccharina japonica), and D5 (Gracilaria lemaneiformis), respectively. Growth performance of shrimp in D5 diet was significantly higher than that of shrimp fed the control and D4 diet (P < 0.05); however, there is no significant difference among D2, D3, and D5 diets (P > 0.05). Apparent digestibility coefficients of dry matter from the D2, D3, and D5 diets were significantly higher than that from the control and D4 diets (P < 0.05). Supplementary macro-algaes enhanced hepatopancreas immunity through positively increasing total antioxidant status (TAS) and prophenoloxidase activity (ProPO), as well as up-regulating the hepatopancreas RNA expression of ProPO and IκBα and down-regulating the expression of transforming growth factor β. Furthermore, dietary macro-algaes modified intestinal microbiota of L. vannamei, boosting the relative abundance of beneficial bacterial such as Bacteroidetes, Firmicutes, and Bacillaceae, and decreasing those detrimental bacterial such as Gammaproteobacteria and Vibrionaceae. In the white spot syndrome virus (WSSV) challenge trial, shrimps were injected for 6-day after the rearing trial. On the fourth day, shrimp death started to occur, and the mortality in D2, D3, and D5 diets was significantly lower than that in control and SJ diets during 4-6 challenged days (P < 0.05). Dietary macro-algaes ameliorated hepatopancreas damage in L. vannamei by increasing TAS and ProPO activities and decreasing SOD activity, inhibiting the lipid peroxidation (malondialdehyde), as well as regulating the immune-related genes expression. Taken together, dietary macro-algaes availably relieved enterohepatic oxidative damage by improving antioxidant ability and immunity and regulated intestinal microbiota in L. vannamei. These results indicated that G. lemaneiformis is the most suitable macro-algae and then followed by U. pinnatifida and P. haitanensis as the feed ingredient for L. vannamei.
The marine unicellular microalga Porphyridium sp. synthesizes several bioproducts consisting of sulphated polysaccharides, arachidonic acid and phycoerythrin, of which sulphated polysaccharides prominently exhibit antiviral, anticancer, anti-inflammatory, antioxidative and immunomodulatory properties. This study aimed at appraising the feasibility of Porphyridium sp. in diets for Trachinotus ovatus. Three experimental diets were formulated to contain 0 (PS0), 10 (PS1) and 50 g/kg (PS5) Porphyridium sp. powders. After 6 weeks of feeding trials, the supplementation of Porphyridium sp. significantly boosted the growth performance and activities of digestive enzymes (pepsin and lipase). Fish fed with PS1 and PS5 diets showed greater villus length than those fed with PS0 diet. The antioxidant capacity of fish fed the diet with Porphyridium sp. powders was pronouncedly enhanced via stimulating the Nrf2-ARE pathway and elevating antioxidant enzyme activities. Moreover, Porphyridium sp. supplementation not only promoted liver health of fish by suppressing mRNA levels of pro-inflammatory cytokines and apoptotic genes, but significantly boosted non-specific immunity via up-regulating the mRNA levels of c-type lysozyme and complement C4 and down-regulating the mRNA levels of heat shock protein 70. These results suggest that microalga Porphyridium sp. promotes the growth performance and immune function, and thereby strengthens the health of T. ovatus.
A nutritional feeding experiment was conducted to evaluate the effects of shrimp paste on feeding attractiveness, growth performance, digestive enzyme activities, immune-related genes and intestinal morphologyin hybrid snakehead (Channa maculata ♀ × Channa argus ♂). Two diets were formulated with or without shrimp paste supplementation (D1:0% and D2: 3%) to feed fish for 8 weeks. Results showed that growth performance (FBW, WG and SGR) and feed intake significantly increased with shrimp paste supplemented (P0.05). Gut lipase and amylase activity was significantly higher in diet supplemented with shrimp paste than that in control group (P0.05). Results showed that feeding diet with shrimp paste supplemented did not significantly up-regulate expression of GR, IκB, P65 and IL8 (P>0.05). There are significantly more goblet cells in shrimp paste supplemented diet than that in control diet (P0.05). The results indicated that dietary 3% shrimp paste supplementation improved the growth performance of hybrid snakehead by enhancing feed intake while made no difference to antioxidant capacity.
In recent years, the dramatically high lipid level has been used in fish feeds, resulting in low survival rates of fish and huge economic losses. Based on these issues, a six-week feeding experiment was conducted to investigate whether diet supplements with L-carnitine can be used to relieve detrimental impacts on growth performance, hepatic lipid accumulation, antioxidant, anti-inflammatory and non-specific immune status, as well as intestinal morphology of Trachinotus ovatus, fed on a high-fat diet. Three isonitrogenous diets were formulated to either include or exclude high-fat and L-carnitine (lipid positive (LP): 130 g kg−1 lipid, lipid negative (LN): 210 g kg−1 lipid, lipid negative with L-carnitine (LNC): 210 g kg−1 lipid with 0.6 g kg−1 L-carnitine). Results indicated that the growth performance and mid-intestine villi length of T. ovatus in the LN group were significantly lower than that of the LP group (p < 0.05), while significantly higher growth performance and better mid-intestine morphology of fish in the LNC group was found compared to the LN group (p < 0.05). mRNA expression levels of hepatic genes associated with the inflammatory and non-specific immune statue of T. ovatus in the LN group were significantly higher compared with the LP group (p < 0.05), while that of the LNC group was significantly lower compared with the LN group (p < 0.05). Hepatic triglyceride content and lipid droplets in the LN group were significantly elevated, compared with the LP group (p < 0.05). On the contrary, diet supplemented with L-carnitine could mitigate hepatic lipid accumulation in fish caused by a high-fat diet. Regarding antioxidant states, higher malondialdehyde content in the LN group (p > 0.05) and significantly higher levels in the LNC group (p < 0.05) were found, compared with the LP group, while no statistical difference was found between the LN and LNC groups (p > 0.05). In conclusion, L-carnitine can relieve the detrimental impact on growth performance of T. ovatus exposed to a high-fat diet treatment by reducing hepatic lipid accumulation and improving intestinal morphology, anti-inflammatory and non-specific immune status, but could not mitigate oxidative pressure.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
