Effect of fish meal replacement by Chlorella meal with dietary cellulase addition on growth performance,digestive enzymatic activities,histology and myogenic genes’ expression for crucian carp Carassius auratus

This study was conducted to investigate the effects of fish meal (FM) replacement by Chlorella meal (CM) with dietary cellulase supplementation on growth performance, digestive enzymatic activities, histology and myogenic genes’ expression in crucian carp Carassius auratus (initial body weight: 2.90 ± 0.02 g, mean ± SEM). Six isonitrogenous diets were formulated at two cellulase levels (0 and 2 g kg^?1). At each cellulase level, CM was added at three levels of 0, 533.1 and 710.8 g kg^?1 to substitute 0, 75 and 100% of dietary FM respectively. Each experimental diet was randomly assigned to triplicate groups with 25 juvenile fish per fibreglass tank for 8 weeks. Dietary CM substitution significantly increased growth, feed utilization, amylase activity and the expression of Myod, Mrf4 and Myf5, but reduced the Myog expression. Dietary cellulase addition increased hepatosomatic and viscerosomatic index, lipase activity and the expression of Mrf4, but reduced trypsin activity and the expression of Myog and Myf5. Dietary CM substitution enlarged the cell size and also caused some karyopyknosis in liver. Our results showed that CM could totally replace FM in diets; dietary cellulase supplementation at the level of 2 g kg^?1 played a subtle role in improving growth and feed utilization for crucian carp.     

Fishmeal can be totally replaced by a mixture of rapeseed meal and Chlorella meal in diets for crucian carp (Carassius auratus gibelio)

This study was conducted to investigate the effects of dietary fishmeal (FM) replacement by a mixture of rapeseed meal and Chlorella meal (RCM) on growth performance, apparent digestibility coefficients (ADCs), digestive enzymatic activities and intestinal histology of crucian carp Carassius auratus gibelioi. Five isonitrogenous diets were formulated to replace 0% (RCM0), 25% (RCM25), 50% (RCM50), 75% (RCM75), and 100% (RCM100) of protein from fishmeal with RCM respectively. Each experimental diet was randomly assigned to triplicate groups with 25 juvenile fish (initial body weight: 1.77 ± 0.04 g) per fibreglass tank for 6 weeks. With increasing substitution levels, weight gain rate, specific growth rate, feed intake and protein efficiency ratio increased, but feed conversion rate decreased. Dietary RCM substitution improved lipid content of muscle, but had no significant effect on other proximate composition of muscle and liver. ADCs of dry matter, protein, lipid, energy and the majority of amino acids increased with increasing substitution level, and digestive enzyme activities (amylase, trypsin and lipase) in intestine showed the similar trend with ADCs. Dietary RCM substitution had no significant adverse effect on intestinal histology. This study indicated that FM protein could be completely replaced by mixed protein sources (RCM) in crucian carp diets.     

Replacement of Fishmeal by a Mixture of Soybean Meal and Chlorella Meal in Practical Diets for Juvenile Crucian Carp,Carassius auratus

A growth trial was conducted to evaluate the effect of a mixture of soybean meal and Chlorella meal (SCM) as a dietary fishmeal (FM) substitute on growth performance, apparent digestibility coefficients (ADCs), digestive enzymatic activities, and histology of juvenile crucian carp, Carassius auratus. Five isonitrogenous and isoenergetic diets were formulated to replace 0 (SCM0), 25 (SCM25), 50 (SCM50), 75 (SCM75), and 100% (SCM100) of protein from FM with SCM, respectively. The diets were fed to triplicate groups of juvenile crucian carp for 6 wk. Weight gain, specific growth rate, feed intake, protein efficiency ratio, and intestinal digestive enzymatic activities (amylase, trypsin, and lipase) tended to decline with increasing FM replacement levels (P > 0.05). Dietary SCM substitution significantly influenced dry matter content in muscle, and crude protein and lipid contents in liver (P < 0.05). ADCs for dry matter, protein, lipid, energy, and most amino acids showed no significant differences between the control and SCM25 group, but tended to decline with replacement levels over 25%. Higher SCM substitution (50–100%) caused karyopyknosis and necrosis in liver, but intestinal histology did not show noticeable pathological changes. The present study indicated that FM could be replaced by 25% of SCM, without significant adverse growth performance, feed utilization, and histology of crucian carp.     

Effects of dietary cellulase addition on growth performance,nutrient digestibility and digestive enzyme activities of juvenile crucian carp Carassius auratus

This study was conducted to determine the effects of dietary cellulase addition on improving the nutritive value of Chlorella for juvenile crucian carp Carassius auratus (initial body weight: 2.99 ± 0.02 g, mean ± SEM). Five isonitrogenous and isoenergetic experimental diets were formulated to contain 0.0 (control), 0.5, 1.0, 1.5 and 2.0 g kg^?1 cellulase, respectively. Each experimental diet was randomly assigned to triplicate groups with 25 juvenile fish per fibreglass tank for 8 weeks. The results showed that weight gain, specific growth rate, feed intake and the trypsin activity in the anterior intestine increased with increasing dietary cellulase to 1.5 g kg^?1 and then declined with further addition. However, the mRNA expression levels of Mrf4 and Myf5, the apparent digestibility coefficients for dry matter, protein, energy and the majority of amino acids, and the activity of lipase in the anterior intestine were highest in fish fed the 1.0 g kg^?1 cellulase diet, and then tended to decline with further cellulase supplementation. In conclusion, the optimal dietary cellulase supplementation level was 1.0–1.5 g kg^?1, which can improve growth performance, digestive activities and nutrient digestibility in crucian carp.     

Response of juvenile tench (Tinca tinca L.) fed practical diets with different protein contents and substitution levels of fish meal by soybean meal

A basal practical diet for juvenile tench (Tinca tinca) was formulated and elaborated to test several protein contents and substitution possibilities of fish meal (FM) by soybean meal (SBM) in a 90‐day trial with 5‐month‐old juveniles (30.54 mm TL, 0.30 g W). A factorial design included nine feeding treatments: three protein contents (50%, 40% or 30%) and three levels of replacement (0%, 25% or 45%) of FM protein by SBM protein. In addition, a commercial carp feed was used as reference. Final survival ranged from 98.2% to 99.4%. The 50% dietary protein with 0% or 25% replacement and 40% dietary protein with 25% replacement diets enabled higher growth (P < 0.05) and lower FCR (P < 0.05) than the rest of practical diets. Fish fed 50% dietary protein had similar growth than those fed carp feed (63.8% protein). Deformed fish averaged 1% for the practical diets and 87.6% for the carp feed. The basal practical diet has showed to be feasible and levels of 40–50% dietary protein with 25% replacement of FM protein by SBM protein can be recommended for juvenile tench aged 5–8 months.     

Effects of β‐conglycinin on growth performance,antioxidant capacity and intestinal health in juvenile golden crucian carp,Carassius auratus

The objective of this study was conducted to research the effects of β‐conglycinin in the diets on the growth performance, immunity function, antioxidant capacity and intestinal health of juvenile golden crucian carp (Carassius auratus). Five diets contained respectively (0, 20, 40, 60 and 80 g/kg) β‐conglycinin, and were used to feed juvenile golden crucian carp for 56 days. Final weight, weight gain and specific growth rate were significantly reduced by dietary β‐conglycinin (20–80 g/kg). Feed efficiency and protein efficiency were significantly reduced by dietary β‐conglycinin (40–80 g/kg). In hepatopancreas, the activities of T‐SOD, ACP, ALT and T‐AOC were significantly suppressed by dietary β‐conglycinin (20–80 g/kg). The activities of LZM, AKP, CAT and GPx were significantly reduced by dietary β‐conglycinin (40–80 g/kg). The activities of protease were significantly reduced and the content of MDA was significantly increased by dietary β‐conglycinin (60–80 g/kg). In proximal intestines, the activities of protease and CAT were significantly decreased by dietary β‐conglycinin (40–80 g/kg). In mid and distal intestines, the activities of protease and CAT were significantly inhibited by dietary β‐conglycinin (20–80 g/kg). In intestines, T‐AOC and GPx were significantly declined by dietary β‐conglycinin (20–80 g/kg). In proximal and mid intestines, the content of MDA were significantly increased by dietary β‐conglycinin (40–80 g/kg). In distal intestines, the content of MDA was significantly increased by dietary β‐conglycinin (20–80 g/kg). The expression of IGF‐I was significantly decreased and the expression of IL‐1β and TNF‐α was significantly increased by dietary β‐conglycinin (20–80 g/kg). The structural integrity of intestinal tissues were damaged by dietary β‐conglycinin (20–80 g/kg), the part of intestinal villus were shed, the part of epithelial cells were separated from lamina propria. Ultimately, these results suggested dietary β‐conglycinin should be <20 g/kg in formula feed of golden crucian carp.     

Dietary available phosphorus requirement of crucian carp,Carassius auratus

This study was carried out to evaluate the dietary available phosphorus (AP) requirement for crucian carp (Carassius auratus). Triplicate groups were fed diets containing five graded levels of AP in 15 recirculating tanks. After a 9‐week feeding experiment, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and whole‐body and vertebrae P contents were significantly increased as dietary AP increased from 1.1 to 7.6 g/kg (p < .05) and then levelled off. N and P retention was also significantly increased as dietary AP increased to 5.5 g/kg (p < .05). Condition factor, viscerosomatic index, hepatosomatic index, whole‐body moisture, muscle P content and plasma total cholesterol were not affected by dietary P levels (p > .05). Protein and ash contents of the whole body increased linearly as the dietary P level increased, but the lipid content, plasma alkaline phosphatase activities and triacylglycerol contents showed an inverse relationship. Based on WG, FE, whole‐body P content and vertebrae P content, the optimum requirement of dietary AP for crucian carp was estimated to be 8.3, 8.3, 8.0 and 7.8 g/Kg, respectively.     

Effects of Dietary Inclusion of Chlorella vulgaris on Growth,Blood Biochemical Parameters,and Antioxidant Enzyme Activity in Olive Flounder,Paralichthys olivaceus

This study was carried out to investigate the effects of dietary inclusion of defatted Chlorella on growth performance, body composition, blood biochemistry, and antioxidant enzyme activity in olive flounder. Four isonitrogenous (51% crude protein) diets were formulated to contain 0 (control), 5, 10, or 15% Chlorella meal (CM) (designated as Con, CM5, CM10, and CM15, respectively) and fed to triplicate groups of fish (104.4 g) to apparent satiation twice daily for 8 wk. At the end of the feeding trial, significant enhancement (P < 0.05) in growth performance was obtained at over 10% CM compared to fish fed the control diet. No significant changes in dorsal muscle and liver proximate composition were found following CM administration. The groups fed CM‐containing diets revealed significantly lower plasma cholesterol concentration than those fed the control diet. Dietary CM affected antioxidant enzyme activity; significantly higher plasma catalase activity was found in fish fed ≥10% CM and total antioxidant capacity increased in CM5 and CM10 groups compared to the control. However, plasma glutathione peroxidase and superoxide dismutase activities were not significantly influenced by dietary CM. Also, significant enhancement in 1,1‐diphenyl‐2‐picryl‐hydrazyl radical scavenging activity was found in dorsal muscle of fish fed CM15 diet compared to the control. The findings in this study showed that dietary inclusion of 10–15% CM can enhance growth performance and affect antioxidant enzyme activity and lipid metabolism in olive flounder.     

The effects of partial replacement of fishmeal protein by hydrolysed feather meal protein in the diet with high inclusion of plant protein on growth performance,fillet quality and physiological parameters of Pengze crucian carp (Carassius auratus var. Pengze)

Goal of this research is to explore the effects of graded dietary levels of hydrolysed feather meal (HFM) protein as an alternative of fishmeal protein on Pengze crucian carp (Carassius auratus var. Pengze). Five isonitrogenous (35% crude protein) diets were formulated as Control diet and four other diets F15, F30, F45 and F60 wherein 15%, 30%, 45% and 60% fishmeal protein replaced by HFM protein fed for 70 days. The results showed that fish growth was unaffected up to 45% fishmeal protein replacement. Dietary HFM protein could reduce the crude protein composition of body and further affect fillet quality through a significant increase in springiness, gumminess, chewiness and/or resilience. Activity of digestive enzymes (amylase, lipase and tryptase) increased as the fishmeal protein replacement increased, whereas a higher replacement level had negative impacts on absorptive capacity of intestine by decreasing its absorptive area, following by a reduction in concentration of lactate dehydrogenase, total cholesterol, high‐density lipoprotein, low‐density lipoprotein and ammonia in serum. Although intestinal antioxidant parameters were elevated by dietary HFM protein , the content of malondialdehyde in intestine was also positively associated with the protein replacement level. Overall, our results indicate that up to 45% of fishmeal protein could be replaced by HFM protein in diet without significant impact on the growth of Pengze crucian carp, whereas the crude protein content of whole body, fillet quality and oxidative status would significantly be affected when the replacement level of fishmeal protein reaches 30% together with a negative effect on the intestinal histology.     

Effect of substitution of dietary fish meal by soybean meal on different sizes of gibel carp (Carassius auratus gibelio): digestive enzyme gene expressions and activities,and intestinal and hepatic histology

A 7‐week growth trial was conducted to evaluate the effects of dietary soybean meal (SBM) on digestive enzyme activity of intestinal mucosa, mRNA levels of digestive enzymes in hepatopancreas, and the mid‐intestinal and hepatopancreas histology of gibel carp CAS III (Carassius auratus gibelio). Four different growth phases of gibel carp (initial body weight: fry, 0.8 g; juvenile, 5.0 g; 1‐year‐old, 62.7 g; and broodstock, 135.6 g) were tested. Seven isonitrogenous and iso‐energetic diets were formulated to contain different SBM replacement levels (0%, 20%, 40%, 60%, 80% and 100% of dietary fish meal protein), and another diet (SBMAA) contained all SBM protein and supplied crystalline amino acids. The results showed that the activities of mid‐intestine trypsin, α‐amylase and gamma glutamyl transpeptidase reduced with increased dietary SBM, while the chymotrypsin activity increased first and then decreased. The ultrastructures of intestinal epithelial cells and hepatopancreas cells in fry and broodstock fish were distinctly affected by 200 g kg^‐1 dietary SBM. Supplementation of dietary amino acid to the highest replacement groups was not sufficient to improve digestive and absorptive capacities and growth performance. Gibel carp may be adapted to dietary SBM through increase in gene expression of hepatopancreas digestive enzymes and has potential to utilize proceeded SBM as feedstuffs.     

Effect of Varying Carbohydrate Fractions on Growth,Body Composition,Metabolic, and Hormonal Indices in Juvenile Black Carp,Mylopharyngodon piceus

This study was conducted to investigate the effects of varying carbohydrate (CHO) fractions on growth, body composition, metabolic, and hormonal indices in juvenile black carp, Mylopharyngodon piceus. Juvenile black carp, M. piceus (average weight: 1.5 ± 0.05 g) were fed with graded levels of dietary available CHO (0.06, 10.65, 19.43, 28.84, 37.91, and 47.38%) for 9 wk, respectively. Results showed that the highest weight gain could be obtained at 24.98% dietary CHO using second‐order polynomial regression model; and optimal dietary available CHO content (28.84%) could significantly increase the final body weight and the protein efficiency ratio (PER) while reducing the feed conversion ratio (FCR) (P < 0.05). Dietary available CHO could gradually increase the hepatosomatic index, the crude lipid contents in the whole body and the glucose and triglyceride content in the plasma. The activities of glycolysis enzymes and glucose‐6‐phosphate dehydrogenase could be increased with increasing dietary available CHO. The activities of glucose‐6‐phosphatase and fructose‐1,6‐bisphosphatase were firstly decreased at 10.65% dietary available CHO and increased to stable level at 19.43% dietary available CHO. In addition, both 19.43 and 28.84% dietary available CHO could increase the adiponectin contents in the plasma of black carp, M. piceus. Meanwhile, both 19.43 and 28.84% dietary available CHO could significantly increase the mRNA expression levels of growth hormone, insulin, ghrelin, neuropeptide Y, somatostatin I, and somatostatin II in juvenile black carp, M. piceus, compared with the CHO‐deficient diet (0.06%). These results suggest that optimal inclusion of dietary CHO fractions (19.43–28.84%) could improve metabolic homeostasis and promote growth and feed efficiency in juvenile black carp, M. piceus.     

Effect of substitution of dietary fishmeal by soya bean meal on different sizes of gibel carp (Carassius auratus gibelio): nutrient digestibility,growth performance,body composition and morphometry

Four 70‐day growth trials were performed to investigate the effects of substitution of dietary fishmeal (FM) by soya bean meal (SBM) in different sizes of gibel carp CASIII (Carassius auratus gibelio). The initial weights of fry, juvenile, 1‐year fish and broodstock of gibel carp were 0.8, 5.0, 62.7 and 135.6 g, respectively. In each trial, eight diets were formulated to be iso‐nitrogenous and iso‐energetic, and different levels of soy bean meal protein were used to replace fishmeal protein at 0%, 20%, 40%, 60%, 80% and 100%. Another diet containing all SBM protein and supplemented with crystalline amino acids was also tested. The results showed that apparent digestibility coefficients (ADCs) of dry matter and energy decreased with SBM substitution while the ADCs of phosphorus increased. The ADCs of protein of high SBM substitution were higher than those of FM groups. Juveniles show lower ADCs than grown‐up fish. Dietary SBM substitution showed negative effects on survival, growth and feed utilization in gibel carp. One‐year fish and broodstock gibel carp have relatively higher tolerance to dietary SBM than fry and juveniles.     

Effects of dietary selenium on growth performance and oxidative stress in juvenile grass carp Ctenopharyngodon idellus

An 8‐week feeding trial was conducted to investigate the effect of dietary selenium (Se) on feed intake, weight gain and antioxidant activity in juvenile grass carp (11.2 ± 0.03 g). Six Se levels (0.13, 0.41, 0.56, 1.12, 2.18 and 4.31 mg/kg) of semi‐purified diets were assayed in triplicate. The maximum weight gain, specific growth rate and feed intake were obtained in fish fed with 1.12 mg Se/kg diet. Hepatic glutathione peroxidase activity was markedly increased when dietary Se ≤1.12 mg/kg diet and reached a plateau when dietary Se ≥1.12 mg/kg diet. Hepatic superoxide dismutase and serum catalase activities in juvenile grass carp fed with 0.56, 1.12 and 2.18 mg Se/kg diets were all significantly higher than those in the other groups. The malondialdehyde content in liver and serum was firstly decreased and then increased with increasing dietary Se content, and the lowest content was observed in fish fed with 1.12 mg Se/kg diet. With the increase in Se level, the activities of serum alanine aminotransferase and aspartate aminotransferase were reduced. In addition, serum alkaline phosphatase activity and albumin content were highest in fish fed with 1.12 mg Se/kg diet. This study indicated that both the Se deficiency and excess of Se caused negative effect on the oxidative stress in juvenile grass carp and suggested that the health‐giving concentration of dietary inorganic Se was 1.12 mg/kg diet. Moreover, based on the broken‐line regression analysis of weight gain, the optimal concentration of dietary inorganic Se was 0.83 mg/kg for juvenile grass carp.     

The antioxidant status,apoptosis, intercellular integrity and immune function of grass carp (Ctenopharyngodon idella) head kidney and spleen fed different levels of pyridoxine

This study was carried out to investigate the effects of dietary pyridoxine (PN) on the antioxidant status, apoptosis, intercellular integrity and immune function of head kidney and spleen in young grass carp (Ctenopharyngodon idella). Results showed that compared with the optimal PN level, (a) PN deficiency decreased antioxidant enzyme activities and down‐regulated the mRNA levels of antioxidant enzymes, NF‐E2‐related factor 2 (Nrf2), myeloid cell leukaemia‐1 (Mcl‐1) and tight junction proteins, whereas it increased the contents of reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC), and up‐regulated the mRNA levels of cysteinyl aspartic acid‐protease (caspase), Fas ligand (FasL), p38 mitogen‐activated protein kinase (p38MAPK) and myosin light chain kinase (MLCK) in the head kidney and spleen of fish (p < .05). (b) PN deficiency decreased lysozyme (LZ) and acid phosphatase (ACP) activities, and complement contents, and down‐regulated the mRNA levels of antibacterial peptides, anti‐inflammatory cytokines, inhibitor of κBα (IκBα) and target of rapamycin (TOR), whereas it up‐regulated the mRNA levels of pro‐inflammatory cytokines and nuclear factor kappa B p65 (NF‐κBp65) in the head kidney and spleen of fish (p < .05). (c) Dietary PN requirements of grass carp based on the malondialdehyde content and lysozyme activity were estimated as 4.97 and 4.99 mg/kg diet, respectively.     

Dietary lysine requirement of juvenile Pseudobagrus ussuriensis

An 8‐week feeding trial was conducted to determine dietary lysine requirement of juvenile Pseudobagrus ussuriensis (initial body weight: 0.60 g). Six isonitrogenous (crude protein, 400 g/kg) and isolipidic (crude lipid, 50 g/kg) diets were formulated to contain graded levels of dietary lysine (12.8, 19.9, 26.5, 34.0, 40.8 and 44.1 g/kg dry diets, respectively). The results indicated that weight gain, specific growth rate, productive protein value and protein efficiency ratio increased, while feed conversion ratio decreased with increasing dietary lysine level up to 34.0 g/kg dry diet and then levelled off. Fish fed diet with 12.8 g/kg lysine had the lowest lysine content (58.6 g/kg dry matter) in muscle, while fish fed diet with 34.0 g/kg lysine had the highest value (61.6 g/kg dry matter; p < .05). Broken‐line analysis on the basis of weight gain showed that the optimal dietary lysine requirement for maximum growth of juvenile Pseudobagras ussuriensis is 33.5 g/kg dry diet (82.4 g/kg dietary protein). Quadratic regression analysis of protein efficiency ratio against dietary lysine levels indicated that the optimal dietary lysine requirement of juvenile Pseudobagras ussuriensis is 36.4 g/kg dry diet (89.5 g/kg dietary protein).     

Graded replacing fishmeal with canola meal in diets affects growth and target of rapamycin pathway gene expression of juvenile blunt snout bream,Megalobrama amblycephala

A feeding trial was conducted to assess the effects of replacing fishmeal (FM) with canola meal (CM) on the growth performance, feed utilization and related gene expression of juvenile blunt snout bream (Megalobrama amblycephala). Fishes were fed with five isonitrogenous (330 g/kg crude protein) and isoenergetic (15 MJ/kg) diets for 16 weeks, which was graded replacing levels of fishmeal (replacing 0, 37.5, 75, 112.5 and 150 g/kg FM with CM). The results revealed that specific growth rate, feed efficiency ratio and protein efficiency ratio of the groups with replacement level up to half were significantly higher than the others, while feed intake was inverse. Peptide transporter 1 (PepT1) mRNA level in the gut was significantly up‐regulated in groups CM25 and CM50 compared to other groups. Relative gene expression of IGF‐1 among groups was extremely significant based on the nonparametric test. Replacement of FM with CM caused a reduction in the hepatic expression of target of rapamycin (TOR), while significant increase trends were observed in hepatic genes of protein kinase B (AKT) and eIF4‐binding protein (4E‐BP2). However, TOR gene expression in the gut was significantly up‐regulated first and then down‐regulated, while mRNA levels of 4E‐BP2 and S6K1 in the gut were first significantly decreased and then increased in CM75, finally significantly decreased to the lowest. The overall results indicated that up to 75 g/kg FM could be replaced by CM (350.5 g/kg CM) in the diets for juvenile blunt snout bream. Besides, these signalling molecules could explain further the mechanisms that juvenile blunt snout can only maintain optimal growth performance up to 75 g/kg FM replacement with CM.     

Comparative study on the effect of high dietary carbohydrate on the growth performance,body composition,serum physiological responses and hepatic antioxidant abilities in Wuchang bream (Megalobrama amblycephala) and black carp (Mylopharyngodon piceus Richardson, 1846)

A 90‐day trial investigated the effect of dietary carbohydrate level on growth performance, body composition, serum physiological responses and hepatic antioxidant abilities of a herbivorous fish, Wuchang bream (Megalobrama amblycephala) and a carnivorous fish, black carp (Mylopharyngodon piceus Richardson, 1846). For each species, two isonitrogenous and isolipidic semi‐purified diets (28.6% crude protein and 5.3% crude lipid for Wuchang bream) were formulated to contain 30.4% and 52.9% carbohydrate (WB‐NCHO and WB‐HCHO); Two isonitrogenous and isolipidic semi‐purified diets (32.6% crude protein and 5.3% crude lipid for black carp) were formulated to contain 20.5% and 40.5% carbohydrate (BC‐NCHO and BC‐HCHO). It was shown that, compared to Group WB‐NCHO, Wuchang bream in Group WB‐HCHO had lower weight gain rate, specific growth rate, serum total protein, hepatic superoxide dismutase activity and total antioxidative capacity, while higher feed conversion ratio, serum triglyceride and cortisol levels (P < 0.05). Compared to Group BC‐NCHO, black carp in Group BC‐HCHO had lower final weight, weight gain rate, specific growth rate, protein efficiency ratio, serum alkaline alkaline phosphatase activity, serum total protein, hepatic superoxide dismutase activity and total antioxidative capacity, while higher feed conversion ratio, whole body crude lipid, serum triglyceride, cholesterol, glutamic‐oxaloacetic transaminase activity and cortisol levels (P < 0.05). The results of this study suggested that Wuchang bream had better capacity of utilizing dietary carbohydrate than that of black carp, while high levels of dietary carbohydrate might not only be detrimental to growth performance and feed utilization but also the immune response and health for both species.     

Dietary soybean β‐conglycinin suppresses growth performance and inconsistently triggers apoptosis in the intestine of juvenile grass carp (Ctenopharyngodon idella) in association with ROS‐mediated MAPK signalling

The current study aimed to investigate the effects of dietary soybean β‐conglycinin on growth performance and intestine apoptosis in juvenile grass carp (Ctenopharyngodon idella). For fish fed with the 80 g β‐conglycinin/kg diet for 7 weeks, the specific growth rate and feed intake were decreased. In the proximal intestine, dietary β‐conglycinin did not induce DNA fragmentation, tended to decrease the reactive oxygen species (ROS) content, and decreased ROS‐generating enzyme (NADPH oxidase [NOX]) activity. Subsequently, in the mid‐intestine, dietary β‐conglycinin caused DNA fragmentation, tended to increase the ROS content, increased caspase‐3, caspase‐8 and caspase‐9 activities, upregulated the mRNA levels of proapoptotic molecules (apoptotic protease‐activating factor‐1 [Apaf1] and Bcl‐2‐associated X protein [BAX]) and mitogen‐activated protein kinase (MAPK)‐related signal molecules (Jun N‐terminal kinase (JNK) and p38 MAPK) and increased the protein levels of p38 MAPK and phospho‐p38 MAPK. Moreover, in the distal intestine, dietary β‐conglycinin induced DNA fragmentation, elevated NOX activity and the ROS content and increased caspase‐3, caspase‐8 and caspase‐9 activities, death ligand (TNF‐α) mRNA expression level, and p38 MAPK and phospho‐p38 MAPK protein levels. In summary, dietary soybean β‐conglycinin suppressed fish growth and inconsistently caused apoptosis among the different intestinal segments which was partially associated with ROS‐mediated MAPK signalling.