Effects of dietary protein on growth performance,nutrient utilization,digestive enzymes and physiological status of grey mullet,Mugil cephalus L. fingerlings reared in inland saline water

A 60 days feeding trial was conducted to illustrate the effect of graded levels of protein on the growth and metabolic enzymes of grey mullet (Mugil cephalus L.) fingerlings reared in inland saline water (ISW). Six isoenergetic (16 MJ/kg) and isolipidic (60 g/kg) diets containing 240, 260, 280, 300, 320 and 340 g crude protein (CP)/kg diet were formulated and fed to triplicate. Weight gain %, specific growth rate, protein utilizing efficiency, feed efficiency and RNA:DNA ratio were significantly higher (p < .05) in 320 and 300 g CP/kg diets. Fish fed with 240 g CP/kg diet showed significantly higher (p < .05) feed intake, whole‐body lipid content, hepatosomatic index value and liver glycogen content. Transaminase enzymes and malate dehydrogenase activities were elevated in fish fed 340 g CP/kg diet. Protease activity increased with increasing dietary CP level, but amylase activities showed an inverse relationship. No significant (p > .05) variations were observed for lactate dehydrogenase, oxidative stress enzymes, blood parameters and serum osmolality among all the treatment groups, but red blood cell count increases with increasing dietary CP levels. Based on the results, feeding dietary protein level of 300 g CP/kg is economically viable for rearing of grey mullet in ISW.     

Effects of γ‐aminobutyric acid supplementation on the growth performance,serum biochemical indices and antioxidant status of pharaoh cuttlefish,Sepia pharaonis

This study evaluated the effects of dietary γ‐aminobutyric acid (GABA) on the growth performance, serum biochemical indices and antioxidant status of pharaoh cuttlefish, Sepia pharaonis. Cuttlefish were cultured in open‐culturing cement pool systems for 8 weeks. Six practical diets supplemented with graded levels of GABA (0, 20, 40, 60, 80 and 100 mg/kg) were formulated. Each diet was randomly assigned to triplicate groups of 60 cuttlefish (mean weight: 10.33 g), the cuttlefish were fed two times per day to apparent satiation. The results showed that the specific growth rate (SGR), weight gain (WG) and feed efficiency (FE) significantly increased with dietary GABA supplementation (p < .05). The survival rate (SR) and protein content in muscle significantly increased when 58.9 mg/kg GABA supplied. Moreover, the nitric oxide (NO) content and acid phosphatase (ACP) activity in serum were significantly increased with dietary GABA supplementation (p < .05), while the activity of aspartate aminotransferase (AST) in serum decreased significantly when supplied with GABA at 58.9 mg/kg (p < .05). In addition, dietary GABA improved antioxidation activity by significantly increasing the activities of superoxide dismutase (SOD) and catalase (CAT) but decreasing malondialdehyde (MDA) levels in the liver and gill (p < .05). On the basis of the quadratic regression analysis of FE, the optimum content of dietary GABA in S. pharaonis was estimated to be 55.3 mg/kg. The findings of this study demonstrated that dietary GABA had a positive effect on the growth performance, serum biochemical indices and antioxidant status of S. pharaonis.     

Effects of fish meal replaced by fermented soybean meal on growth performance,intestinal histology and microbiota of largemouth bass (Micropterus salmoides)

This study was conducted to investigate the effects of replacing fish meal (FM) with fermented soybean meal (FSM) and soybean meal (SM) on growth performance, intestinal histology and microbiota of largemouth bass (Micropterus salmoides). The basal diet contained 350 g/kg FM (CON), and then, FM was replaced with SM and FSM at the ratios of 30% and 60% (SM‐30, SM‐60, FSM‐30 and FSM‐60), respectively. The largemouth bass (4.43 ± 0.13 g) were fed for 8 weeks. The results showed that weight gain of fish fed with FSM‐60 and SM‐60 diets was significantly lower, and feed conversion ratio of SM‐30, SM‐60 and FSM‐60 groups was significantly higher than the CON group (p < .05). The intestinal villus height of SM‐60 group and the villus width of SM‐60 and FSM‐60 group were significantly lower than the CON group (p < .05). The 30% FM replacement by SM and FSM significantly increased the abundance of Cetobacterium and Mycoplasma, respectively (p < .05). In conclusion, FSM could replace 30% FM in diet without negative impacts on the growth performance of largemouth bass, while the SM should be controlled below 30%.     

Dietary Moringa oleferia leaf meal induce growth,innate immunity and cytokine expression in grass carp,Ctenopharyngodon idella

The present research was designed to investigate the growth promoting and immunostimulating properties of Moringa oleferia leaf meal (MLM) in grass carp. Juvenile grass carp (22.03 g ± 1.164) were fed with diets supplemented with 0, 50, 100 and 150 g/kg MLM for 48 days. At the end of feeding trial, skin mucus was used for analysis of lysozyme, protease, antiprotease and peroxidase activity. Head kidney was used for expression analysis of tumour necrosis factor‐alpha, interleukin‐8 and interferon‐γ. The obtained results showed that fish fed with 100 and 150 g/kg MLM had significant increase in weight gain and specific growth rate (p < .05). However, condition factor was not altered. The MLM (50 and 100 g/kg) inclusion resulted in higher mucus lysozyme and protease activity (p < .05), while peroxidase activity increased only in fish fed with 100 g/kg MLM and antiprotease activity was not altered. Expression of tnf‐α increased in a dose‐dependent manner, and significant (p < .05) increase was recorded in fish fed with 150 g/kg MLM. The expression of il‐8 and ifn‐γ increased in fish fed with 50 and 150 g/kg MLM; however, the increase was not significant (p > .05). In conclusion, supplementing juvenile grass carp feed with MLM up to 150 g/kg has growth promoting and immunostimulating effects.     

Effects of fish origin probiotics on growth performance,immune response and intestinal health of shrimp (Litopenaeus vannamei) fed diets with fish meal partially replaced by soybean meal

This study was conducted to evaluate the application of four fish origin probiotics to relieve the side effects induced by SBM in shrimp. Shrimps were fed with high fish meal diet (C0, positive control containing 500 g/kg FM and 0 g/kg SBM), low fish meal diet (C, control containing 250 g/kg FM and 340 g/kg SBM) or the control diet (C) supplemented, respectively, with 1.0 × 10⁸ CFU/g Bacillus pumilus SE5 (T1), Psychrobacter sp. SE6 (T2), Enterococcus faecium MM4 (T3) or Bacillus claussi DE5 (T4). After 6 weeks of feeding, the growth performance, hepatopancreatic digestive enzymes, intestinal histological structure and immune parameters were determined. The results showed that compared with high FM group (C0), significantly lower WGR and SGR as well as higher FCR were observed in the low FM group (C) (p < .05). Compared with the control, significantly lower FCR was observed in treatment T1 (p < .05), but not in treatments T2–T4. Protease, amylase and lipase activities in all the treatments (T1‐T4) were significantly higher than the control (p < .05). GOT and GPT activities in the control were significantly lower than the C0 (p < .05), while higher MDA level was recorded in the control (p < .05). Meanwhile, higher GPT activities were observed in treatments T1‐T4 compared with the control (p < .05). Compared with the C0, lower SOD, ACP and AKP activities were observed in the control. Significantly improved SOD and AKP activities were observed in all probiotic feeding groups compared with the control (p < .05). The control diet led to significant reduction of intestinal wall thickness and villus height compared with the C0 (p < .05), while significantly higher intestinal wall thickness and villus height were exhibited in all the probiotic groups compared with the control (p < .05), except intestinal wall thickness in treatment T3. Thus, these results demonstrated that the four fish origin probiotic strains could relieve the side effects induced by high level of SBM in shrimp, while probiotic B. pumilus SE5 showed the best performance.     

Dietary lysine requirement of juvenile Protonibea diacanthus

An 8‐week experiment was conducted to determine the optimal dietary lysine requirement for juvenile Protonibea diacanthus. Six isonitrogenous and isolipidic diets were formulated to contain levels of 10.8 (L10.8), 18.2 (L18.2), 26.1 (L26.1), 33.9 (L33.9), 40.7 (L40.7) and 48.6 g/kg (L48.6) of diets and were fed to the juvenile Protonibea diacanthus, respectively. The results indicated that weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and final weight (FW) increased as the dietary lysine level increased from 10.8 to 26.1 g/kg and then decreased as the dietary lysine levels further increased (p < .05). The lowest feed conversion ratio (FCR) was found when dietary lysine level was 26.1 g/kg. Analysis of specific growth rate by two slope broken‐line model indicated that the estimated optimal dietary levels of lysine for juvenile Protonibea diacanthus was 23.06 g/kg (51.24 g/kg dietary protein).     

Effects of alternative dietary lipid sources on growth performance,health status and fillet fatty acid composition of hybrid sturgeon (Acipenser baeri Brandt ♀ × Acipenser schrenckii Brandt ♂)

An 8‐week trial was conducted to determine the effects of total replacement of 12.9% fish oil (FO) with soybean oil (SBO), peanut oil (PNO), sunflower seed oil (SFSO), corn oil (CO) and canola oil (CNO) on growth performance, health status and fillet fatty acid composition of hybrid sturgeon (194.28 ± 0.14 g). Compared to the FO group, dietary SBO decreased growth performance (p < .05), increased serum glucose and hepatic lipid content (p < .05). No obvious adverse effects on growth performance and health status were observed in PNO, SFSO and CO groups (p > 0.05). The fish fed with CNO had increased growth performance (p < .05), reduced serum ALT, AST, LDL‐C (p < .05) and enhanced serum GSH‐Px, T‐AOC, and LZM, MPO, C4 (p < .05). The contents of C18:1n9, C18:2n6, and ∑n‐3 PUFA and ∑n‐6 PUFA in fillets showed a positive linear correlation with the diets (p < .05). In summary, PNO, SFSO and CO are probable alternative lipid sources to fully replace FO. Hybrid sturgeon prefers to use CNO as a lipid source with improved growth performance and health status. The fillet fatty acid composition mirrors the dietary fatty acid composition.     

Lipid metabolism in juveniles of Yellowtail,Seriola dorsalis,fed different levels of dietary methionine containing a low level of cholesterol: Implication in feed formulation

The involvement of dietary methionine in the lipid metabolism of Seriola dorsalis, at different levels of dietary methionine (Met), and low content of cholesterol was investigated. Four diets containing different Met levels and a low amount of cholesterol (0.23 g/kg diet) were prepared. One hundred and eighty juveniles (16.2 ± 1.5 g) were randomly distributed into each 12 500‐L ponds. After 60 days, the growth in weight (%) significantly increased following the Met supplementation, whereas SGR of all the experimental treatments was higher than the Basal Diet. The expression of the insulin‐like growth factor (IGF‐1) increased significantly (0.2‐fold) and was complemented by significant changes in Mat, BHMT and HMG‐CoA, for fish that were in the low and higher Met levels. The cholesterol content in the whole body and liver increased following methionine supplementation, similarly to that observed for crude lipids, in particular in the whole body and liver tissues. However, the relative amount of most fatty acids remained unchanged. Only the oleic acid increased at a higher amount of Met. Therefore, once the dietary requirement of methionine is met, the methionine is used to synthesize cholesterol. It is recommended to supply a higher amount of methionine to spare energy for growth.     

Effects of bioflocs with different C/N ratios on growth,immunological parameters,antioxidants and culture water quality in Opsariichthys kaopingensis Dybowski

Biofloc technology (BFT) is a new ecological aquaculture technology that is intended not only to eradicate pollutants and elevate feed utilization but also to enhance immunity and antioxidant activity in aquatic animals. A 28‐day feeding trial was implemented to evaluate the effects of promoted bioflocs on the water quality, growth performance, immunological parameters and antioxidant status of Opsariichthys kaopingensis Dybowski juveniles in low exchange culture tanks. Three hundred sixty healthy O. kaopingensis juveniles (7.1 ± 0.02 g) were irregularly distributed among 12 tanks. Four C:N ratios in triplicate tanks were tried: C/N = 10.8:1 with a commercial diet (control), C/N = 15:1, C/N = 20:1 and C/N = 25:1. Anhydrous glucose (99.97%) was added to the commercial diet to maintain elevated carbon ratio in the three treatments. Uninterrupted 24‐hr aeration was supplied during the test by using an air‐stone connected to an air pump to develop the bioflocs in the water column. The results indicated that BFT significantly reduced total ammonia nitrogen (TAN), nitrite (NO2^?‐N), total phosphorus (TP) concentrations and water transparency (Secchi depth) in C/N 15, C/N 20 and C/N 25 (p < .05), whereas the chemical oxygen demand (COD) and nitrate nitrogen (NO3^?‐N) concentrations gradually increased over time. In addition, weight gain, specific growth rate (SGR), survival and protein efficiency ratio (PER) were significantly elevated in C/N 20, while food conversion rate (FCR) was considerably decreased (p < .05) in C/N 20, compared with the control. Significant increases in lysozyme (LSZ), glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT) and alkaline phosphatase (AKP) activities of O. kaopingensis were found in the C/N 20 group after a 28‐day feeding trial (p < .05). Comparing the antioxidant capacity of O. kaopingensis in gills, brains, kidneys, hepatopancreas, intestines and serum of juveniles from the four experimental groups, the activity of superoxide dismutase (SOD), total antioxidant capacity (T‐AOC), catalase (CAT) activity and glutathione peroxidase (GSH‐PX) activity of juveniles in the C/N 20 group were significant higher (p < .05), and the content of malondialdehyde (MDA) was considerably lower, than in the control. Overall, these findings suggest that BFT not only can enhance O. kaopingensis growth performance and strengthen antioxidant status but also can upgrade immune response, ensuring the sustainable development of aquaculture.     

Partial replacement of fishmeal with Clostridium autoethanogenum single‐cell protein in the diet for juvenile black sea bream (Acanthopagrus schlegelii)

Clostridium autoethanogenum protein (CAP) is a single‐cell protein derived from ethanol production and may have potential to become a substitute for fishmeal in aquafeeds. A 70‐day feeding trial was conducted with black sea bream (Acanthopagrus schlegelii) (mean initial weight 6.03 ± 0.09 g) to evaluate partial replacement of fishmeal with CAP in diets. Seven isonitrogenous and isoenergetic diets were formulated with graded levels of CAP (0, 4.85, 9.70, 14.55, 19.40, 38.80 and 58.20%) to replace fishmeal. The inclusion of CAP at all dietary levels tested did not significantly affect the growth performance (p > .05). Fish fed the CAP58.20% diet showed a significantly lower feeding rate, with significantly higher protein efficiency ratio and feed efficiency ratio compared with fish fed the other diets (p < .05). No statistical differences were found in dorsal muscle and whole‐body compositions. Total superoxide dismutase in serum of fish fed CAP58.20% diet was significantly lower compared with that of the control. Malondialdehyde, catalase, total antioxidant capacity and digestive enzyme activities revealed no significant differences among dietary treatments. Phosphorus retention efficiency significantly increased, and phosphorus discharge showed a downward trend with increasing CAP inclusion levels. In conclusion, the results indicated that CAP is a safe and effective alternative protein source, which can replace fishmeal in the diet of black sea bream up to 58.20%, without adverse effects on growth performance, antioxidation and digestive enzyme activity. This study has shown the potential of converting industrial waste into a high protein feed ingredient for aquafeeds.