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Dietary betaine supplementation has been reported to alleviate the adverse effects of high‐carbohydrate diets on Megalobrama amblycephala, while the regulatory mechanism remains largely unknown. In the present study, a 79‐day feeding trial was conducted with 450 juvenile Megalobrama amblycephala (average weight 6.75 ± 0.10 g), which were fed with five high‐carbohydrate diets (43%) supplementing betaine at 0% (CD group), 0.2% (0.2Bet group), 0.4% (0.4Bet group), 0.8% (0.8Bet group), and 1.6% (1.6Bet group), respectively. Results showed M. amblycephala in 0.8Bet group exhibited the best growth performance, indicated by the largest weight gain ratio (142.88%) and least feed conversion ratio (1.63). Moreover, liver health was promoted in 0.8Bet group, with decreased number of non‐nucleated cells and less lipid accumulation, which was accompanied by the lowest hepatosomatic index (1.38%). In order to further illustrate the regulatory mechanism, metabolites assay indicated that dietary betaine supplementation significantly increased plasma contents of methionine, serine, hypotaurine, and taurine, but did not affect plasma contents of cystathionine, cystine, or cysteic acid. Accordingly, the mRNA expressions of cysteine sulfinate decarboxylase in cysteine sulfinic acid pathway and cysteamine dioxygenase (ADO) in sulfinic acid (CS) pathway, which were both involved in taurine synthesis, were also upregulated in the liver. Meanwhile, the microbial communities in M. amblycephala intestine were more stable and uniform with betaine supplementation. Therefore, dietary betaine supplementation may exert its protective roles in improving feed efficiency and liver health of M. amblycephala via promoting de novo taurine synthesis and stabilizing intestinal microbial communities. [ABSTRACT FROM AUTHOR]

Pikeperch (Sander lucioperca) is a species with great potential for aquaculture in Eurasian countries, while feed costs limit the scale of pikeperch farming. Adding carbohydrates to the feed as an energy source is a viable approach to reduce costs and to improve the culture status of pikeperch. In this study, in order to determine the optimal carbohydrate requirement of pikeperch, three tapioca starch (8%, 10%, and 12%) added feeds were produced with isonitrogenous (51%) and isolipidic (11%). For 8 weeks, body weight was 1.20 ± 0.01 g, pikeperch were manually fed the trio of experimental diets until they seemed fully satisfied. The finding revealed that pikeperch can utilize dietary carbohydrate, but excessive dietary carbohydrate will adversely affect the growth performance. The growth and survival rate were decreased in pikeperch in S12 (P < 0.05). The α‐amylase activity of S12 reduced in the intestine and lipid deposition was observed in the liver compared with the S8. In addition, proinflammatory cytokines, interleukin 1 beta (il1-β), interleukin 8 (il8), and tumor necrosis factor beta (tnf-β), in the liver and intestine elevate and anti‐inflammatory cytokines, interleukin 10 (il10) and transforming growth factor beta (tgf-β), decrease with increasing dietary carbohydrate levels. Hepatic and intestinal antioxidant capacity were also adversely affected, with S12 significantly increasing malondialdehyde (MDA) contents and decreasing glutathione (GSH) and total antioxidant capacity (T‐AOC) (P < 0.05). The intestinal barrier function is also damaged, the height and width of intestinal villi decreased, and the expression of occludin-a, occludin-b, and zonula occludens‐2 (zo-2) genes was decreased. Elevated levels of starch intake led to harm to gut microflora, reducing bacterial populations, simultaneously boosting the presence of detrimental bacteria (Proteobacteria, Actinobacteriota, Achromobacter, and Rhodococcus) and diminishing the beneficial bacteria (Firmicutes). In conclusion, moderate addition of starch as an energy source can reduce feed costs; however, over addition can bring about organism damage and is recommended to be added at less than 10%. [ABSTRACT FROM AUTHOR]

To explore the effects of dietary threonine on growth and ovarian development of red swamp crayfish (Procambarus clarkii), crayfish (5.48 ± 0.19 g) were fed six isoproteic and isoenergetic diets with varying levels of threonine (7.16 g/kg (control), 9.19, 12.74, 16.44, 20.83, and 23.78 g/kg) for 8 weeks. The results showed that weight gain rate, feed conversion ratio, protein efficiency rate, protein deposition rate, and essential amino acid deposition rates obtained the optimal values when the dietary threonine level was 12.74 or 16.44 g/kg. Compared to the control group, the 12.74 g/kg group exhibited enhanced nonspecific immunity and antioxidant properties. The 16.44 g/kg group demonstrated a significant increase in the frequency of B cells and R cells in the hepatopancreas, the length and width of intestinal villi, and the activities of protease and lipase. It also showed elevated ecdysterone hormone, gonadal index (GI), cAMP content, and the relative abundance of beneficial intestinal microflora. Compared to the control group, the mRNA expression of mTOR, S6K1, 4EBP1, EcR, RXR, chitinase, PKA, Vg, cdc2, and cyclin B was significantly upregulated, and the mRNA expression of MIH was significantly downregulated in the 16.44 g/kg group. Overall, optimal dietary threonine could improve intestinal health, regulate immune function, and enhance protein utilization, molting, and growth performance of red swamp crayfish. Additionally, it improved the synthesis of yolk substance and facilitated the development of ovarian cells of female crayfish. The optimal threonine level was 14.87–16.94 g/kg (dry matter), corresponding to 42.51–48.42 g/kg of dietary protein in red swamp crayfish. [ABSTRACT FROM AUTHOR]

The trial was conducted to investigate the effects of the replacement of dietary fishmeal (FM) by the blend of Tenebrio molitor meal (TMM), Chlorella meal (CM), Clostridium autoethanogenum protein (CAP), cottonseed protein concentrate (CPC) on growth, protein utilization and intestinal health of gibel carp (Carassius gibelio, CAS Ⅴ). The FM-based diet was used as the control, and the blended proteins (TMM: CM: CAP: CPC) at ratios of 1 : 1:8 : 2 (BLEND A), 1 : 1:6 : 4 (BLEND B), and 1 : 1:4 : 6 (BLEND C) were used to replace FM at three levels (33%, 67%, 100%), respectively. The results showed that, compared to the control group, growth performance increased significantly when dietary FM was fully replaced by BLEND B (P < 0.05), while decreased by BLEND A (P < 0.05). The complete substitution of FM with BLEND B significantly upregulated the mRNA expression of intestinal proinflammatory cytokines, anti-inflammatory cytokines, and tight junction-related genes (P < 0.05), improving intestinal tissue morphology and health. And it also significantly increased intestinal trypsin activity (P < 0.05), upregulated the mRNA expression of amino acid sensory receptor-related and amino acid or peptide transport-related genes (P < 0.05), increased protein apparent digestibility coefficient (P < 0.05). The 100% substitution of FM with BLEND A significantly upregulated the mRNA expression of intestinal proinflammatory cytokines and downregulated the mRNA expression of anti-inflammatory cytokine il-10 (P < 0.05), reduced intestinal villus height (P < 0.05), and decreased protein apparent digestibility coefficient (P < 0.05). In conclusion, BLEND B could completely substitute dietary FM and was beneficial to the growth and health of gibel carp. Dietary digestible essential amino acids index (DEEAI) was found as an important indicator and should be higher than 79.5% to meet the maximum growth of fish. [ABSTRACT FROM AUTHOR]

To investigate the effects of tea polyphenols (TPs) on the growth and carbohydrate metabolism of grass carp (Ctenopharyngodon idella), 0 (control group), 250, 500, 1000, 2000, and 4000 mg kg−1 TPs were added to the basal diet and fed to grass carps for 8 weeks. The results show that 500 mg kg−1 group exhibited the significantly highest feed conversion efficiency (FCE) and specific growth rate (SGR) (p <.05) and significantly higher activities of pyruvate kinase (PK), lactate dehydrogenase (LDH), malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) (p <.05). The livers of the control group and 500 mg kg−1 group were subjected to RNA‐Seq, and the expressions of glycogen phosphorylase (PYG) and sucrase‐isomaltase (SI) genes were upregulated, while that of glucose‐6‐phosphatase (G6PC) was downregulated, and these promoted glycogen catabolism. The expressions of glucokinase (GK), PK, 6‐phosphofructokinase (PFK), glucose‐6‐phosphate 1‐dehydrogenase (G6PD) and fructose‐bisphosphate aldolase A (ALDOA) genes were upregulated to promote glucose catabolism. The results indicate that 500 mg kg−1 TPs could upregulate the expressions of some genes that promote carbohydrate decomposition, increase the activities of carbohydrate decomposition enzymes and enhance the utilization of carbohydrates, thereby improving the FCE and SGR. [ABSTRACT FROM AUTHOR]

An 8‐week feeding experiment was performed to evaluate the effects of dietary arachidonic acid (ARA) on the reproductive performance, tissue fatty acid profile and sex hormone secretion in female Pelteobagrus fulvidraco during the breeding season. Three diets with different ARA levels (0.64%, 4.67% and 10.07% of total fatty acids) were formulated, a control diet (C) and two diets with low ARA (ARA‐L) or high ARA (ARA‐H). The results showed that the highest gonadosomatic index (GSI) and condition factor (CF) were observed in the ARA‐H group. The diets with supplementation of ARA resulted in a significantly higher fertilization rate, more normal larvae and greater survival rate of 7 days posthatching (7DPH) larvae. The ARA contents in liver and 3DPH larvae were improved with increasing dietary ARA concentrations. The lowest EPA/ARA ratios were observed in liver and eggs of fish fed with the ARA‐L diet. Significantly reduced serum estradiol (E2), 11‐keto‐testosterone (11‐KT) and testosterone (T) levels were found in the ARA‐L group females compared with the other treatments. The combined results indicated that a higher dietary ARA level and ARA/EPA ratio mainly influence spawning performance and egg quality of yellow catfish and that ARA regulates sex steroid hormone synthesis in broodstock. [ABSTRACT FROM AUTHOR]

An 8‐week feeding trial was conducted to evaluate the effect of replacement of dietary fishmeal with cottonseed meal (CSM) on the growth performance and health status of juvenile grass carp, Ctenopharyngodon idellus (6.67 g). Six isonitrogenous and isoenergetic diets were formulated with different CSM levels (0, 121, 241, 362, 482 and 603 g/kg diet). The first limiting amino acid was methionine, which decreased with an increase in dietary CSM from 361 to 538 g/kg. When the dietary CSM content was lower than 241 g/kg, the limiting amino acid was histidine. Thermal growth coefficient (TGC) and feed efficiency first increased and then decreased (p < 0.05), which was consistent with the change in the limiting amino acid. The feeding rate increased with a rise in the dietary CSM level (p < 0.05). The activity of digestive enzymes except trypsin decreased significantly (p < 0.05), serum aminotransferase activity and triglycerides increased, serum cholesterol decreased (p < 0.05). When dietary CSM was raised to 362 g/kg, intestinal villi and hepatopancreas tissue were injured. When the dietary CSM was 603 g/kg, alternative complement pathway haemolytic activity was inhibited (p < 0.05). The gossypol level in dorsal muscles from each treatment was below the detection limit. Based on the quadratic regression analysis of the TGC, the optimal dietary CSM level was 175.9 g/kg, and the maximum could be up to 351.8 g/kg and still result in the same TGC as that of control group. [ABSTRACT FROM AUTHOR]

An 8‐week growth trial was conducted to investigate the effects of non‐genetically modified (nGM) soybean (Youchun 06‐1) and genetically modified (GM) soybean (Roundup Ready®) with and without a heat treatment on the growth and health of three Cyprinidae species with different feeding habits (grass carp Ctenopharyngodon idellus, gibel carp Carassius auratus gibelio, and black carp Mylopharyngodon piceus; body weight: 283.0 ± 2.0 g, 60.5 ± 0.7 g, and 261.4 ± 3.1 g). Five diets (FM, nGMS, hnGMS, GMS, and hGMS) were made with fishmeal and full‐fat soybean (Youchun 06‐1, heat‐treated Youchun 06‐1, Roundup Ready®, and heat‐treated Roundup Ready®). The FM diet contained fishmeal as the sole protein source. The experimental diets contained full‐fat soybean meal as 60% of dietary protein. Both temperature (60, 80, 100, and 120°C) and duration (1 and 2 hr) of heating influenced trypsin inhibitor activity (TIA) and protein solubility of nGM soybean and GM soybean. The TIA in GM soybean was higher than that in nGM soybean. After heating at 120°C for 2 hr, each amino acid of soybean treatment showed a slight decline. Neither source of soybean nor heat treatment affected the growth performance, feed utilization, chemical composition of the whole fish body and muscle, and lipase or amylase activity of the three Cyprinidae species (p > 0.05). Heat treatment of soybean meal slightly increased the plasma antioxidant capacity of the three fish and plasma cholecystokinin of black carp and grass carp. The unheated soybean treatment adversely affected the height and density of black carp intestinal villi, and all the soybean treatments caused disruption of the grass carp intestinal epithelium. [ABSTRACT FROM AUTHOR]

Abstract: A 57‐day growth experiment was conducted with juvenile gibel carp (13.48 ± 0.10 g) in a flow‐through system to study the effect of dietary phosphorus on growth performance, body composition, nutrition utilization, phosphorus loading and enzymes activities. Seven semipurifed diets were formulated to contain 0.07 (the basal), 2.27, 5.32, 8.10, 12.06, 15.24 and 19.48 g available phosphorus/kg diet. The results showed that specific growth rate, body length and feed efficiency significantly increased in the fish fed diets containing 0.07 to 15.24 g available P/kg diet (p < .05). Ash and P content increased in fish fed diets containing 0.07–12.06 P g/kg (p < .05) and then levelled off, while moisture, crude protein and lipid had no significant difference (p > .05). The protein retention efficiency increased in the fish fed with diets 0.07–5.32 g/kg P (p < .05) and then reached a plateau. The P content in faeces was higher in fish fed diets containing 15.24 and 19.48 g available P/kg. Total P concentration in tank water increased in fish fed 0.07–12.06 g available P per kg diet (p < .05). The plasma P was higher in the fish fed with 15.24 g available P/kg diet (p < .05), triglycerides was lower in the fish fed diet containing 15.24 and 19.48 g available P/kg (p < .05), no significant differences were observed in plasma Ca, plasma glucose and calcitonin (p > .05). Based on SGR, whole body P content and FE, dietary available P requirement for juvenile gibel carp were 13.37, 13.97 g/kg and 15.06 respectively. [ABSTRACT FROM AUTHOR]

Abstract: An 88‐day experiment was conducted in a flowing system to evaluate the effects of dietary vitamin C on growth, body composition, antioxidant and gonad development of on‐growing gibel carp. Triplicate tanks of gibel carp (77.2 ± 0.1 g) were randomly fed with one of seven experimental diets containing l‐ascorbic acid of 0, 101.1, 188.5, 313.1, 444.1, 582.1 and 747.0 mg/kg, respectively. The results showed that specific growth rate (SGR) and feed efficiency (FE) of fish were not affected by dietary l‐ascorbic acid. Dietary l‐ascorbic acid of 444.1 mg/kg diet led to low levels (p < .05) of gonadosomatic index (GSI) and hypothalamic gonadotropin‐releasing hormone (GnRH) in on‐growing fish, as well as the early ovarian stages (Developing stages) compared with fish (Maturing stages) from the other groups. Dietary l‐ascorbic acid supplementation increased (p < .05) the dorsal muscle collagen content, but did not affect the protein or lipid content of dorsal muscle in gibel carp. Plasma total antioxidant capacity (T‐AOC) and superoxide dismutase (SOD) activity increased (p < .05) and then remained unchanged with the increase in dietary l‐ascorbic acid levels. Dietary l‐ascorbic acid of 101.1 mg/kg diet improved (p < .05) plasma lysozyme activity of the fish. Broken‐line regression indicated that dietary l‐ascorbic acid requirement of 77 g gibel carp was 223.3 or 225.0 mg/kg diet based on plasma T‐AOC or SOD activity, which was a little higher than that based on plasma l‐ascorbic acid concentration (193.2 mg/kg). [ABSTRACT FROM AUTHOR]

A 12-week growth trial was conducted in a flow-through system to determine dietary selenium (Se) requirement for on-growing gibel carp (initial body weight: 76.2 ± 0.05 g, mean ± SEM). Selenomethionine was supplemented to the basal diet to formulate seven semi-purified diets containing 0.26, 0.58, 0.72, 1.14, 1.34, 1.73 and 2.09 mg Se kg−1 diet. The results showed that plasma superoxide dismutase (SOD) activity significantly increased when fish were fed with 0.58 mg Se kg−1 diet ( P < 0.05) and then decreased at 2.09 mg Se kg−1 diet ( P < 0.05). Plasma T-AOC activity was higher in fish fed with 0.72 mg Se kg−1 diet ( P < 0.05) and plasma malondialdehyde (MDA) was higher in fish fed with 0.26 mg Se kg−1 diet ( P < 0.05). When fish were fed 1.14 mg Se kg−1 diet, hepatic GSH-Px, T-AOC, GSH and CAT activities were significantly higher than those fed with 0.26 mg Se kg−1 diet ( P < 0.05). Hepatic superoxide dismutase (SOD) activity was higher at 1.34 mg Se kg−1 diet ( P < 0.05). Fish liver Se concentrations were significantly higher when fed with 0.72 mg Se kg−1 diet ( P < 0.05) and then kept constant when Se ≥ 0.72 mg kg−1 ( P > 0.05). Whole-body and muscle Se concentrations were higher when fed with 1.34 mg Se kg−1 diet ( P < 0.05) and kept a plateau when Se ≥ 1.34 mg kg−1 ( P > 0.05). In conclusion, based on broken-line regression of hepatic Se concentrations, hepatic SOD activity and hepatic T-AOC activity, dietary Se requirements for on-growing gibel carp was 0.73 mg kg−1, 1.12 mg kg−1 and 1.19 mg kg−1 diet respectively. [ABSTRACT FROM AUTHOR]

An 84-day growth trial was designed to investigate effects of dietary replacements fish oil with pork lard ( PL) or rapeseed oil ( RO) on growth and quality of gibel carp ( Carassius auratus gibelio var. CAS III) (initial body weight: 158.2 ± 0.2 g), and responses of the fish refed fish oil ( FO) diet. Three isonitrogenous (crude protein: 30%) and isolipid (crude lipid: 10%) diets were formulated containing 7.73% FO, PL or RO. Five experimental treatments including FO group ( FO), PL group ( PL), RO group ( RO), group fed PL for 42 days and refed FO for 42 days ( PL+ rFO), RO and refed FO group ( RO+ rFO) was tested. At the end of first 42 days, the fish fed PL and RO had higher mortality than that of the control ( P > 0.05). At the end of whole experiment, fish fed PL and RO showed higher plasma cortisol than FO fish ( P < 0.05). RO+ rFO fish showed higher lysozyme activity than RO fish ( P < 0.05). Fish growth and feed utilization, composition of whole body and muscle, free amino acids, texture, off-flavour substances or sensory attributes were not affected by dietary treatments ( P > 0.05). PL and RO diet decreased muscle EPA, DHA and n-3/n-6 ratio ( P < 0.05), while FO-refeeding had recovery effect. It can be concluded that the replacement of FO by PL and RO does not affect the growth, feed utilization or fish tasting quality in gibel carp. Fish muscle fatty acids modified by dietary PL and RO can be recovered by refeeding with FO diet. [ABSTRACT FROM AUTHOR]

A 8 week growth trial of three feeding frequencies (2, 4 and 6 meals day-1) and three dietary protein levels (30%, 34% and 38%) was conducted to investigate the influence of feeding frequency and dietary protein level on growth, feed utilization, serum free essential amino acids (EAA) dynamics and nitrogen (N), phosphorus (P), carbon (C) retention in juvenile allogynogenetic gibel carp (Carassius auratus gibelio) 'CAS III'. The results showed that feeding frequency and dietary protein level increased feed intake (FI), specific growth rate (SGR) and feed efficiency (FE). SGR increased significantly with the increase in feeding frequency and dietary protein level. But, the increase in dietary protein level from 30% to 38% in group 6 meals day-1 did not result in better growth. Compared with the group of 4 meals day-1 × 38%, the fish fed the diet containing 30% crude protein at 6 meals day-1 obtained similar SGR but showed lower FIp (protein intake). Compared with 2 meals day-1, NREs (nitrogen retention efficiency) of 4 and 6 meals day-1 were relatively higher. PRE (phosphorus retention efficiency) and CRE (carbon retention efficiency) increased significantly with feeding frequency while TNW (total nitrogen waste output), TPW (total phosphorus waste output) and TCW (total carbon waste output) decreased significantly. Feeding frequency and dietary protein level increased trypsin activity. Serum free EAA concentrations varied more synchronously at 6 meals day-1 than 2 meals day-1. It could be concluded that increasing feeding frequency could improve growth by increasing feed intake and feed efficiency for juvenile gibel carp. The increase in feeding frequency showed proteinsparing effect. [ABSTRACT FROM AUTHOR]

Two 8-week feeding trials were conducted to evaluate dietary carbohydrate utilization by omnivorous gibel carp (Carassius auratus gibelio) (2.4 ± 0.1 g) and herbivorous grass carp (Ctenopharyngodon idellus) (6.5 ± 0.1 g). Five isonitrogenous (370 g kg -1) and isolipid (70 g kg -1) diets were formulated with increasing corn starch levels (60, 140, 220, 300 and 380 g kg -1). Results showed that specific growth rate (SGR), feed efficiency (FE) and protein retention efficiency (PRE) of gibel carp significantly increased from dietary starch of 60 to 300 g kg -1 and then decreased from 300 to 380 g kg -1, but those of grass carp showed no significant differences between treatments. Independent of dietary starch levels, grass carp gained significantly higher FE and PRE than gibel carp. Feeding rate (FR) of gibel carp was significantly higher than that of grass carp. In two fish species, high dietary starch (300 and 380 g kg -1) tended to obtain higher hepatosomatic index (HSI), serum triglyceride, hepatic lipid and body lipid contents. Serum glucose concentration of grass carp was not affected, while that of gibel carp fed the starch of 300 g kg -1 diet was significantly lower than those of the fish fed other four diets (60, 140, 220 and 380 g kg -1). Grass carp showed high tolerance to dietary starch while dietary corn starch should be no more than 300 g kg -1 for gibel carp. High starch contents may cause lipid accumulation in the liver and body. [ABSTRACT FROM AUTHOR]