The supplementation of nutrient additives in broad bean-based diet improved the growth of “crisped” grass carp,Ctenopharyngodon idellus

To investigate the effects of supplemental nutrient additives in broad bean-based diets on growth, flesh quality, and collagen gene expression of grass carp, five diets were prepared, including complete formula diet (control), soaked broad bean (SBB), and three broad bean-based diets containing 80% broad bean without (BBD1) or with the supplementation of methionine (BBD2), and methionine+vitamins+minerals (BBD3), and were fed to grass carp (171.9 ± 1.1 g), Ctenopharyngodon idellus, for 84 days. The results showed that broad bean-based diets significantly increased weight gain (WG) and reduced the feed conversion ratio (FCR) of grass carp when compared to the SBB (p < .05). The BBD3 group reached levels similar to the WG and FCR of the control group (p > .05). Grass carp fed the BBD3 diet had lower steaming loss of flesh, higher muscle fiber density, and higher collagen content in muscle and skin than the control (p < .05). The relative expressions of COL1A1 and COL1A2 mRNA in muscle and skin were significantly higher in the BBD3 and SBB groups than in other groups (p < .05). In conclusion, the combination of methionine, vitamins, and minerals in broad bean-based diets promoted the growth of “crisped” grass carp and improved flesh quality and collagen gene expression when compared to the control formula diet.     

黄芩素对草鱼生长性能、血清抗氧化指标和肌肉品质的影响

为研究黄芩素对草鱼生长性能、血清抗氧化能力和肌肉品质的影响,在基础饲料中分别添加0(对照组)、0.1、0.2、0.4和0.6 g/kg黄芩素,配制成5组饲料,饲养平均体质量为(75.8±0.24) g的草鱼60 d。结果显示,鱼体增重率与黄芩素含量呈二次曲线关系;在添加0.2 g/kg黄芩素时,鱼体增重率最大(210.1%),较对照组提高了8.63%,而饲料系数较对照组降低0.14;添加0.2、0.4和0.6 g/kg黄芩素显著提高了血清SOD活性,降低了MDA含量,添加0.4 g/kg黄芩素显著提高了血清CAT活性。各组在AKP活性和LZM含量上无显著差异。0.4和0.6 g/kg黄芩素组的肌肉总氨基酸含量和总必需氨基酸含量显著高于对照组,0.6 g/kg黄芩素组的总非必需氨基酸含量也显著高于对照组。各处理组在肌肉水分、粗蛋白、粗脂肪、灰分、胶原蛋白含量、肌肉失水率以及肌纤维密度和直径上差异不显著。上述结果显示,黄芩素可促进草鱼生长,提高血清抗氧化能力。草鱼饲料中黄芩素的添加量推荐为0.2 g/kg。     

Dietary oxidized oils decreased growth,antioxidative capacity,and negatively affected skin color of channel catfish,Ictalurus punctatus

Eight isolipidic diets containing 0, 20, 40, and 60 g/kg oxidized fish oil (OFO) or oxidized soybean oil (OSO) were fed to triplicate groups of channel catfish, Ictalurus punctatus, for 8 weeks to investigate the effects of oxidized oils on growth, body color, and antioxidative capacity. Lower weight gain (WG) was observed in fish fed high levels of oxidized oils (40 and 60 g/kg) (p < .05). At the inclusion of 40 g/kg, OFO group showed lower WG than the OSO group (p < .05). With the increase of dietary oxidized oils, the serum levels of malondialdehyde, total bilirubin, direct bilirubin, and activity of alanine aminotransferase and aspartate aminotransferase significantly increased (p < .05), but the glutathione level decreased (p < .05). Serum superoxide dismutase and catalase activity showed the maximum values at 20 g/kg OFO group and 40 g/kg OSO group, respectively. Compared to the 0 g/kg oxidized oil groups, both dietary oxidized oils increased the b* value (yellowness) of dorsal skin and caudal skin at 40 and 60 g/kg inclusion (p < .05). In conclusion, dietary oxidized oil (≥40 g/kg) decreased the growth and the antioxidative capacity and increased the yellowness of skin. OFO caused more negative effects on channel catfish than OSO at the inclusion of 40 g/kg.     

Effects of dietary chlorogenic acid on growth,flesh quality and serum biochemical indices of grass carp (Ctenopharyngodon idella)

The study was to investigate effects of dietary chlorogenic acid (CGA) on growth performance, flesh quality and serum biochemical indices of grass carp (95.1 ± 0.3 g) (Ctenopharyngodon idella) fed seven different diets, including control diet, Eucommia ulmoides (EU)‐supplemented diet (20 g kg^–1) and CGA‐supplemented diets containing 100, 200, 400, 600 and 800 mg/kg CGA. Contents of collagen and alkaline‐insoluble collagen in muscle and skin were significantly increased by dietary CGA and EU (p < .05). Total essential amino acids (TEAA) and total amino acids (TAA) in muscle of grass carp fed EU diet or 400, 600 and 800 mg/kg CGA diet were significantly higher than those of fish fed control diet and 100 and 200 mg/kg CGA diet (p < .05). Fish fed 200–800 mg/kg CGA showed significantly lower muscle crude lipid content than EU, control and 100 mg/kg CGA groups (p < .05). Fish fed CGA‐supplemented diets (100–800 mg/kg) had significantly higher muscle fibre density and lower muscle fibre diameter than control group (p < .05). In conclusion, supplementation of CGA improved flesh quality of grass carp, and supplemental level of CGA for improving flesh quality and growth was estimated to be 400 mg/kg diet.     

Effects of Dietary Geniposide on Growth,Flesh Quality,and Lipid Metabolism of Grass Carp,Ctenopharyngodon idella

The aim of this study was to investigate effects of dietary geniposide (GP) on growth performance, flesh quality, and lipid metabolism of grass carp, Ctenopharyngodon idella (95.2 ± 0.6 g), fed seven different diets, including a control diet; Eucommia ulmoides (EU)–supplemented diet (20 g/kg); and GP‐supplemented diets containing 100, 200, 400, 600, and 800 mg/kg GP, respectively. Weight gain rate was significantly improved (P < 0.05) and feed conversation ratio was significantly decreased (P < 0.05) by supplementation of EU. Grass carp fed 100–800 mg/kg GP‐supplemented diets showed significantly higher total collagen and alkaline‐insoluble collagen content in muscle than control (P < 0.05). Contents of total collagen and the alkaline‐insoluble collagen content in the skin of grass carp were significantly increased by dietary 600–800 mg/kg GP and EU (P < 0.05). Fish fed diets containing 600–800 mg/kg GP showed significantly lower muscle crude lipid content than the EU, control, and 100–400 mg/kg GP groups (P < 0.05). Fish fed 400–800 mg/kg GP diets had significantly higher muscle fiber density and lower muscle fiber diameter and serum triglyceride level than the control (P < 0.05). In conclusion, supplementation of GP could improve flesh quality, but not growth of grass carp. The supplemental level of GP for improving flesh quality was estimated to be a 400–600 mg/kg diet.     

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.     

Dietary folic acid requirement of fingerling Catla,Catla catla (Hamilton)

The dietary folic acid requirement of fingerling Catla catla (3.4 ± 0.17 g; 7.6 ± 0.41 cm) was evaluated by feeding casein–gelatin‐based isonitrogenous (350 g/kg crude protein) and isocaloric (16.72 kJ/g GE) diets containing different concentrations of folic acid (0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0 mg/kg) to triplicate groups to apparent satiation at 08:00, 12:30 and 17:30 hr for 16 weeks. Absolute weight gain (AWG; 40.07 g/fish), specific growth rate (SGR; 2.25%), feed conversion ratio (FCR; 1.53), protein retention efficiency (PRE; 31.42%) and protein gain (PG; 6.74) improved significantly (p < .05) with increasing folic acid levels up to 0.4 mg/kg diet and then reached a plateau. However, maximum liver folic acid concentration increased up to 0.6 mg/kg diet. Dietary folic acid levels also significantly affected (p < .05) body composition of fish. No significant change (p > .05) in haematological parameters except in fish fed folic acid‐free diet was noted. Antioxidant and immune parameters increased with increasing concentration of dietary folic acid up to 0.4 mg/kg diet. Broken‐line regression analysis of AWG, FCR, PRE, PG, HCT and liver folic acid concentrations of fingerling C. catla against dietary folic acid levels indicated optimum growth, FCR, PRE, PG, HCT and liver folic acid saturation ranging between 0.22 and 0.56 mg/kg diet, respectively.     

Effects of dietary geniposidic acid on growth performance,flesh quality and collagen gene expression of grass carp,Ctenopharyngodon idella

This study was conducted to investigate the effects of dietary geniposidic acid (GA) on growth performance, flesh quality and collagen gene expression of grass carp (Ctenopharyngodon idella). The fish with an initial body weight of 47.1 ± 0.8 g were fed one of the seven diets, including control diet, Eucommia ulmoides (EU)‐supplemented diet (20 g/kg) and GA‐supplemented diets (200, 400, 600, 800 and 1,000 mg/kg GA) for 75 days. The growth performance and muscle proximate composition showed no difference among groups (p > .05). Dietary GA (200–1,000 mg/kg) increased the contents of total collagen and alkaline‐insoluble collagen in skin (p < .05), and high supplementation of GA (600–1,000 mg/kg GA) and EU increased the contents of total collagen, alkaline‐insoluble collagen and total amino acids (p < .05), but reduced the lipid level in muscle (p < .05). In collagen gene expression, EU and 200–1,000 mg/kg GA increased COL1A1 expression in muscle and skin (p < .05), but the expression of COL1A2 was increased only by high supplementation of GA (1,000 mg/kg, or 800–1,000 mg/kg) (p < .05). In conclusion, dietary GA improved the flesh quality of grass carp, and the supplementation level was estimated to be 600 mg/kg diet.     

Comparison study of three compounds in Eucommia ulmoides on growth,flesh quality of grass carp (Ctenopharyngodon idella)

This study was conducted to compare the growth‐promoting and flesh quality ‐improving effects of three active compounds in Eucommia ulmoides (EU) on grass carp (Ctenopharyngodon idella). Four iso‐nitrogenous diets supplemented with 400 mg/kg inclusion of geniposidic acid (GA), chlorogenic acid (CGA), geniposide (GP) and their combination (GA:CGA:GP = 1:1:1, the mixture) were prepared and fed to grass carp (47.1 ± 0.6 g) for 75 days. The results indicated that weight gain was increased by 5.22%, and feed conversion ratio decreased by 0.07 by dietary CGA (p < 0.05). In flesh quality, the four supplementations significantly increased muscle fibre density, total collagen and alkaline‐insoluble collagen in skin, and reduced steaming loss of flesh. In addition, dietary CGA, GP and the active compounds mixture further increased total collagen, alkaline‐insoluble collagen and amino acid in flesh. In collagen genes expression, the expression of COL1A1 in muscle and skin was significantly promoted by the supplementation of GA, CGA, GP and their combination (p < 0.05). In conclusion, the supplementation of GA, CGA, GP and their combination improved the flesh quality of grass carp, and the growth was increased by CGA. CGA played more important roles in growth‐promoting and flesh quality‐improving effects than GP and GA.     

A combination of rapeseed,cottonseed and peanut meal as a substitute of soybean meal in diets of Yellow River carp Cyprinus carpio var

A feeding trial was conducted to evaluate the results of replacing soybean meal (SBM) with other blend plant protein (BP) (rapeseed meal, cottonseed meal and peanut meal) sources on growth, fish body composition, biochemical parameters, non‐specific immune index and gene expression of growth hormone/insulin‐like growth factor‐1 in Yellow River carp Cyprinus carpio. The results showed that the 600 g/kg replacement with BP in diet did not affect the growth performance of Yellow River carp, but the 800 g/kg SBM replacement diet could depress the growth of fish (p < .05). The 800 g/kg SBM replacement diet significantly impacted the superoxide dismutase, malondialdehyde contents, lysozyme, alanine aminotransferase and aspartate aminotransferase activities (p < .05). Fish fed 800 g/kg SBM replacement diet showed lowest insulin‐like growth factor 1 and highest growth hormone level than that of other diets (p < .05). Both gene expression levels of GH and IGF‐I in hepatic showed significant difference among dietary treatments (p < .05), and the lowest GH and IGF‐I mRNA level in liver were found in fish fed 800 g/kg SBM replacement diet (p < .05). In conclusion, no more than 600 g/kg SBM could be replaced by BP in diet of Yellow River carp without adverse effects on the growth performance. However, 800 g/kg SBM replacement with BP in diet inhibited the growth performance, affected some blood parameters and immune response index, and down‐regulated GH and IGF‐1 gene expression of liver in Yellow River carp. Further, GH level in serum was negatively correlated with GH mRNA level in liver; meanwhile, serum concentrations of IGF‐I were positively correlated with hepatic IGF‐I mRNA expressions.     

Influence of dietary black soldier fly (Hermetia illucens Linnaeus) pulp on growth performance,antioxidant capacity and intestinal health of juvenile mirror carp (Cyprinus carpio var. specularis)

This study was conducted to investigate whether dietary supplementation of black soldier fly (Hermetia illucens Linnaeus) pulp (BSFP) affects growth performance, antioxidant capacity and intestinal health of juvenile mirror carp (Cyprinus carpio var. specularis). A total of 270 juvenile mirror carp (13.68 ± 0.02 g) were randomly allotted to five dietary treatments, BSFP0, BSFP25, BSFP50, BSFP75 and BSFP100, in which BSFP was included in the basal diet at 0, 43.7, 87.3, 131 and 174.7 g/kg, respectively. Then, fish were fed to apparent satiation for 8 weeks. Fish growth performance and nutrient utilization were not different among the five groups (p > .05). Increasing BSFP dietary content significantly decreased whole‐body lipid content but increased kidney index (p < .05). The general relative intestine length was significantly higher in the BSFP100 group than the BSFP0 group (p < .05). Increasing BSFP dietary content significantly increased serum catalase activity and decreased malonaldehyde content (p < .05). The intestinal villus height, villus area and muscle layer thickness were significantly lower in the BSFP100 group than the BSFP0 group (p < .05). No significant differences in the activity of intestinal trypsin, lipase and amylase were observed among all groups (p > .05). In conclusion, this study indicated that BSFP at the level below 131 g/kg could be added in diet of juvenile mirror carp without any negative effect on growth performance and intestinal health. Dietary BSFP inclusion at low levels decreased the whole‐body lipid content and increased the antioxidant activity of juvenile mirror carp.     

Growth performance,digestive and absorptive capacity of on‐growing grass carp (Ctenopharyngodon idellus) fed with graded level of dietary fibre from soybean hulls

The present research evaluated the effects of graded levels of dietary fibre on growth, digestive and absorptive capacities, and the potential underlying mechanisms in on‐growing grass carp (Ctenopharyngodon idella). Grass carp (123.00 ± 0.70 g) were fed diets with graded levels of neutral detergent fibre (NDF: 97.8, 119.0, 140.2, 159.4, 181.2 and 201.6 g/kg diet) for 60 days. Besides, a 2‐week digestion experiment was conducted to explore the effect of dietary fibre on the apparent digestibility coefficients (ADC) of feed. The results showed that optimum dietary fibre level (140.2 or 159.4 g/kg diet) increased feed intake, per cent weight gain, specific growth rate and the ADC of dietary protein (p < .05); increased the activities of digestive and brush border enzyme; and up‐regulated intestinal amino acid transporter mRNA levels (SLC1A5 and SLC6A19b, p < .05) partially associated with activation of TOR signalling pathway. However, high dietary fibre levels (NDF levels ≥181.2 g/kg diet) were not conducive to the digestion and absorption of nutrients, resulting in the decline of growth performance. Thus, based on the quadratic regression analysis for per cent weight gain and feed efficiency, the optimum (143.9 and 134.5 g/kg diet) and maximum tolerance (189.8 and 171.2 g/kg diet) levels of dietary NDF were estimated for on‐growing grass carp.     

Cork and guar gum supplementation enhanced the buoyancy of faeces,and protease supplementation alleviated the negative effects of dietary cork on growth and intestinal health of tilapia,Oreochromis niloticus × O. aureus

To evaluate the effects of dietary cork, protease and guar gum on growth, intestinal health and faecal floatability of tilapia, fine or coarse particle cork (0.45–0.60 mm, 0.60–0.83 mm) was included in diets at 0 (control), 20 g/kg, 30 g/kg and 40 g/kg, and then, 0.175 g/kg protease (P) and 3 g/kg guar gum (G) were supplemented to the 40 g/kg coarse particle diet individually or in combination (P + G). Tilapia with an initial body weight of 15.0 ± 0.5 g were fed one of the 10 diets for 60 days. The results showed that weight gain (WG), apparent digestibility coefficient (ADC) of dry matter (DM) and crude protein (CP), intestinal evacuation ratio, intestinal digestive enzyme activity (IDE) and villus height decreased, and floating faeces ratio increased with the increasing cork level in diets. At the same supplementation level, coarse particle groups showed significantly higher floating faecal ratio than fine particle groups (p < .05). Dietary protease increased the WG, ADC of DM, IDE and villus height (p < .05), and guar gum increased floating faecal ratio when compared to 40 g/kg coarse particle group (p < .05). However, the ADC of DM, IDE and villus height of protease group were still inferior to those of control group (p < .05). In conclusion, dietary cork increased the floating faeces ratio, and the coarse particles produced more floating faeces than fine particles. Moreover, the supplementation of guar gum in cork‐supplemented diet further increased the floating faeces ratio. However, dietary cork negatively affected the growth performance of tilapia, which could be partially alleviated by the supplementation of protease.     

The effect of dietary folic acid on flesh quality and muscle antioxidant status referring to Nrf2 signalling pathway in young grass carp (Ctenopharyngodon idella)

To investigate the effect of dietary folic acid on fish flesh quality, muscle antioxidant status and the potential mechanism, young grass carp (Ctenopharyngodon idella) were fed diets containing 0.10–3.12 mg/kg diet of folic acid for 8 weeks. The results showed that optimum folic acid increased muscle contents of protein, lipid, pH, shear force, amino acids, unsaturated fatty acids, hydroxyproline and glutathione, whereas contents of moisture, cooking loss, lactate and saturated fatty acids and cathepsin L activity showed an opposite trend (p < .05). Moreover, optimum folic acid elevated antioxidant enzyme activities and mRNA levels, as well as NF‐E2‐related factor 2 and casein kinase 2 mRNA levels (p < .05). However, optimum folic acid decreased reactive oxygen species (ROS) content and Kelch‐like ECH‐associated protein 1a (Keap1a) and Keap1b mRNA levels (p < .05). Interestingly, excess folic acid induced negative effects on above‐mentioned parameters (p < .05). Summarily, this study indicated that optimum folic acid improved fish flesh quality and muscle antioxidant system associated with Nrf2‐Keap1 pathway. Based on muscle cathepsin L activity and ROS content, the folic acid requirements for young grass carp were 1.87 and 1.80 mg/kg diet, respectively, regarding to the flesh quality and antioxidant status.     

Effect of dietary iron levels on growth,iron concentration in tissues,and blood concentration levels of transferrin and hepcidin in bighead carp (Aristichthys nobilis)

A 60‐day feeding trial was conducted to estimate the effects of dietary iron (Fe) levels on growth, Fe concentration in the liver, spleen, and blood, and transferrin and hepcidin concentrations in the blood of bighead carp (Aristichthys nobilis). The six experimental diets were formulated to contain different Fe levels (0, 43.1, 84.2, 123.3, 162.2 and 203.1 mg/kg of dry diet) using ferrous sulphate (FeSO₄) as the source. The weight gain (WG) and the specific growth ratio (SGR) of A. nobilis fed with a dietary Fe level of 123.3 mg/kg were significantly higher than that of the 0 mg/kg Fe group (p < .05). The results indicated that the growth was affected by dietary Fe levels. Regression analysis of WG and SGR at different levels of dietary Fe suggests that the appropriate dietary requirement of Fe for the bighead carp larvae is 120–134.36 mg/kg. The Fe contents in different tissues were as follows: spleen > liver > whole body. When the Fe dietary content increases to 162.2 mg/kg, the blood concentrations of Fe significantly decreased and thereafter increased, hepcidin significantly decreased and thereafter decreased, and transferrin significantly increased and thereafter decreased. The results indicate that the transferrin blood content significantly increased with decreasing hepcidin of up to 264.63 μg/ml content and thereafter decreased. It could be concluded that after transferrin saturation, hepcidin functions to maintain iron balance in the blood of A. nobilis by decreasing transferrin content.     

Effects of gelatin or carboxymethyl cellulose supplementation during pelleting processing on feed quality,intestinal ultrastructure and growth performance in gibel carp (Carassius gibelio)

Gelatin and carboxymethyl cellulose (CMC) were often used as binders due to their binding ability. To investigate the effects of gelatin and CMC supplementation on feed quality, intestinal ultrastructure and growth performance of gibel carp, six pelleted feed were formulated: control; supplemented with gelatin (10 g/kg, 30 g/kg and 50 g/kg); and supplemented with CMC (10 g/kg and 30 g/kg). Increased gelatin supplementation levels reduced feed solubility and pellet softening (p < .05) and decreased chemical oxygen demand in the surrounding water after pellets were immersed (p < .05). Increased levels of gelatin supplementation enhanced digesta viscosity and reduced intestinal microvilli length and digestive enzymes activities (chymotrypsin and amylase; p < .05) of fish. Fish‐fed diets supplemented with 30 g/kg gelatin had higher levels of plasma total free amino acids and glucose (p < .05) than fish fed 10 g/kg and 50 g/kg gelatin. Feed supplemented with 10 g/kg CMC were softer than those supplemented with 30 g/kg CMC (p < .05); fish‐fed diets supplemented with 10 g/kg CMC had longer intestinal microvilli (p < .05) than fish fed 30 g/kg CMC. Thus, our results indicated that either gelatin or CMC is applicable to supplement in the feed for improving feed quality and without negative effect on growth performance of gibel carp.     

Dietary myo‐inositol requirements of juvenile hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂)

This study was conducted to determine the optimal dietary myo‐inositol (MI) requirement of juvenile hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂). Fish with an initial average body weight of 28.28 ± 0.41 g were randomly divided into six groups with three repetitions in each group and fed the experimental diets with different graded MI concentrations (70.2, 130.0, 270.2, 443.0, 1,096.6 and 1997.3 mg/kg) three times per day for 12 weeks. The results showed that with the increase in dietary MI level from 70.2 mg/kg to 443.0 mg/kg, weight gain (WG) was increased significantly (p < .05); however, when the MI level was further increased, there was no significant difference in weight gain rate (WG) over time (p > .05). Specific growth rate (SGR) showed a similar trend. The feed conversion ratio (FCR), survival rate (SR), hepatosomatic index (HSI), viscerasomatic index (VSI) and condition factor (CF) were not affected by dietary MI supplementation (p > .05). Dietary MI did not affect whole‐body and muscle crude protein and ash content (p > .05), while dietary MI significantly affected the muscle and whole‐body crude lipid and moisture content (p < .05). Moreover, serum triglyceride (TG), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were decreased by increasing dietary MI levels. Total antioxidant capacity (T‐AOC), malonic dialdehyde (MDA) and superoxide dismutase (SOD) activities in the liver were also affected by the dietary MI (p < .05). In summary, this study indicated that the optimal dietary MI requirement for juvenile hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂) was 335.84 mg/kg and 590.65 mg/kg based on the maximum WG and liver MI accumulation indices respectively.     

Effects of hydroalcoholic extract of honeybee pollen on growth performance,flesh quality,and immune and stress response response of rainbow trout (Oncorhynchus mykiss)

The effects of dietary hydroalcoholic extract of honeybee pollen (HBPE) on growth performance, flesh quality, immunity and stress response were investigated. Two hundred fifty‐five rainbow trout (11.14 ± 1.06 g) were fed five diets containing increasing levels of HBPE: control, 0.25HBPE (0.25 g HBPE/kg), 0.5HBPE (0.5 g HBPE/kg), 1HBPE (1 g HBPE/kg) and 1.5HBPE (1.5 g HBPE/kg). After 56 days, rainbow trout fed the 0.5HBPE and 1HBPE diets displayed significantly higher weight gain (49.58 and 53.25 g) and protein efficiency (2.88 and 2.83) compared to those fed the control diet (4.89 and 2.05), respectively (p < .05). For flesh quality, higher protein content in the whole body of fish fed the 1HBPE (633.3 g/kg) and 1.5HBPE (640.9 g/kg) diets was observed when compared to other groups (p < .05). There were no significant differences in the saturated and monounsaturated fatty acid content. Individuals fed the 1HBPE (234.5 g/kg) and 1.5HBPE (234.7 g/kg) diets exhibited higher levels of n‐3 long‐chain polyunsaturated fatty acids in the muscle than the other groups (p < .05). In terms of the immune system, the serum lysozyme and alternative complement pathway haemolytic activity levels in the 0.5HBPE (47.66 and 148.00 U/ml) and 1HBPE (46.00 and 146.33 U/ml) treatments were higher than the other treatments (p < .05). When Aeromonas hydrophila was exposed to different dosages of HBPE, a higher inhibitory zone resulted from 1,000 and 1,500 mg/ml dosage. The lower levels of plasma cortisol were observed in the 1HBPE and 1.5HBPE groups after the complement stress test. Collectively, the present findings suggest that the 1HBPE diet supported superior growth, flesh quality, immunity and stress response of rainbow trout.     

Effects of dietary astaxanthin and vitamin E and their interactions on the growth performance,pigmentation, digestive enzyme activity of kuruma shrimp (Marsupenaeus japonicus)

A 56‐day feeding trial was done to investigate the interactive effects of astaxanthin (Ax) and vitamin E (α‐Toc) on the performance of kuruma shrimp (Marsupenaeus japonicus). A 2 × 3 factorial experiment was conducted with six experimental diets containing two levels of Ax (0 and 0.6 g/kg diet [Ax₀ and Ax_0.6]) and three levels of α‐Toc (0, 0.2 and 1 g/kg diet [α‐Toc₀, α‐Toc_0.2 and α‐Toc₁]). The results indicated that growth performance was significantly (p < 0.05) increased in shrimp fed with the Ax_0.6 × α‐Toc_0.2 diet. Interactive effects between Ax and α‐Toc on the growth parameters were observed. Furthermore, pigmentation performance was significantly (p < 0.05) better in the Ax_0.6 groups. Interaction between Ax and α‐Toc was also found in the Ax content of shrimp body parts. Interestingly, dietary α‐Toc helped to reduce the Ax consumption rate, promote the absorption and increase the deposition of Ax in the muscle. Shrimps from the Ax_0.6 groups showed significantly (p < 0.05) improved hepatopancreatic digestive enzyme activities compared with those of the Ax₀ groups. Although no interactive (p > 0.05) effects were found between dietary α‐Toc and Ax on total haemocyte count and tolerance against freshwater, dietary Ax and α‐Toc supplementation showed better performance on these two parameters. It was concluded that dietary Ax and α‐Toc functioned synergistically, and the shrimp fed with the diet containing 0.6 g Ax/kg diet Ax and 0.2 g α‐Toc/kg diet showed improved growth and pigmentation performance compared with the other groups in the current study.     

Effects of dietary carbohydrate level on growth performance,innate immunity,antioxidant ability and hypoxia resistant of brook trout Salvelinus fontinalis

Juvenile brook trout were fed on six isonitrogenous and isolipidic diets, containing graded levels of gelatinized corn starch (50, 100, 150, 200, 250, 300 g/kg diet) for 81 days. Cellulose was used to compensate carbohydrate loss. The weight gain, specific growth rate and protein efficiency ratio increased as the dietary carbohydrate level increased from 50 to 150 g/kg, but decreased thereafter (p < .05). Quadratic regression analysis revealed that the optimum dietary carbohydrate level was in the range of 187.1–194.1 g/kg. In addition, serum alanine transaminase and aspartate transaminase activities, as well as glucose content, were highest in the group fed on 300 g/kg carbohydrate (p < .05). The hepatic malondialdehyde level increased with dietary carbohydrate levels (p < .05). The hepatic lysozyme activity increased as dietary carbohydrate level increased from 50 to 150 g/kg and decreased thereafter (p < .05). The overall survival rate after hypoxia challenge (45 min; dissolved oxygen content: 2.2 mg L^?1) decreased with dietary carbohydrate levels (p < .05). Taken together, these results suggested that optimal level of dietary carbohydrate could improve growth performance. However, excessive dietary carbohydrate intake (> 250 g/kg) may decrease innate immunity status, increase oxidative stress and reduce resistance to hypoxia stress in brook trout.