Fat deposition pattern and mechanism in response to dietary lipid levels in grass carp, <Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>

This study aimed to evaluate the fat deposition pattern and lipid metabolic strategies of grass carp in response to dietary lipid levels. Five isonitrogenous diets (260 g kg^?1 crude protein) containing five dietary lipid levels (0, 20, 40, 60, 80 g kg^?1) were fed to quadruplicate groups of 15 fish with initial weight 200 g, for 8 weeks. The best growth performance and feed utilization was observed in fish fed with lipid level at 40 g kg^?1. MFI and adipose tissue lipid content increased with increasing dietary lipid level up to 40 g kg^?1, and higher lipid level in diet made no sense. Fish adapted to high lipid intake through integrated regulating mechanisms in several related tissues to maintain lipid homeostasis. In the present study, grass carp firstly increased PPARγ and CPT1 expressions in adipose tissue to elevate adipocyte differentiation and lipolysis to adapt to high lipid intake above 40 g kg^?1. In liver, fish elevated hepatic lipid uptake but depressed biosynthesis of hepatic FAs, resulted in no difference in HSI and liver lipid content among the groups. Only in muscle, fish showed a significant fat deposition when the lipid intake above 40 g kg^?1. The excess lipid, derived from enhanced serum TC and TG contents, was more likely to induce deposition in muscle rather than lipid uptake by adipose tissue in grass carp fed with high dietary lipid, indicating the muscle of grass carp might be the main responding organ to high lipid intake.     

Hemato-immunological responses of Heros severus fed diets supplemented with different levels of Dunaliella salina

In this study, the effects of oral administration of different levels of Dunaliella salina (a natural β-carotene source) on growth parameters, immunological and hematological indices, as well as skin carotenoids, of Heros severus were investigated. One hundred and eighty H. severus weighing 27 ± 0.5 g were divided randomly into four groups in triplicate (15 fish in each replicate). Groups 1–4 received food supplemented with 0, 50, 100 and 200 mg kg^?1 D. salina powder, respectively. After 6 weeks, the growth parameters were compared among the groups. Blood samples were taken from each group, and hematological parameters including red blood cell count (RBC), white blood cell count (WBC), hematocrit (PCV), hemoglobin (Hb) and immunological indices (serum and mucus lysozyme and bactericidal activity, resistance against Aeromonas hydrophila infection) as well as carotenoid content of skin were evaluated. Results showed that some growth indices increased significantly in fish fed with 100 and 200 mg kg^?1 D. salina-supplemented food (P < 0.05). Although serum lysozyme activity was increased in fish fed with food supplemented with 100 and 200 mg kg^?1 D. salina (P < 0.05), no significant change was observed in serum and mucus bactericidal activity and mucus lysozyme activity among the groups (P > 0.05). Most of the hematological parameters such as WBC, RBC, PCV and Hb significantly increased in D. salina-treated fish compared with controls (P < 0.05). Mortality induced after challenge with A. hydrophila in 200 mg kg^?1 D. salina-treated fish was 36.67 %, which significantly decreased compared with control (P < 0.05). Skin carotenoid content in all D. salina treatments was statistically higher than that of control (P < 0.05). Conclusively, D. salina as a food additive can affect positively the growth, immunological and hematological parameters of H. severus.     

Dietary taurine can improve the hypoxia-tolerance but not the growth performance in juvenile grass carp Ctenopharyngodon idellus

This study was conducted to evaluate the effects of dietary taurine, as a feed additive, on the hypoxia-tolerance and growth performance of the juvenile grass carp Ctenopharyngodon idellus, one of the most important and intensively cultured freshwater fish, with the largest production in China. Graded levels of taurine (0, 0.5, 1, 1.5, 2 and 2.5 g kg^–1 dry diet) were fed to grass carp juveniles (mean weight: 5.26 ± 0.03 g) for 8 weeks. The survival time during acute hypoxia increased as dietary levels of taurine increased, with the highest dose of taurine resulting in the best acute hypoxia-tolerance. The erythrocyte osmotic fragility in grass carp was significantly improved when dietary taurine level was at least 1.5 g kg^?1 diet and can be improved much more when dietary taurine level was up to 2.5 g kg^?1 diet. A significant correlation between hemolysis rate of the erythrocyte osmotic fragility test and the survival time of acute hypoxia (r = ?0.873, P = 0.023 < 0.05) strongly suggested that the biomembrane stabilization function of taurine may contribute to its role of enhancing acute hypoxia-tolerance in grass carp. Dietary taurine cannot improve growth performance of grass carp, but it can increase the value of mesenteric fat index, indicating that dietary taurine influences the lipid metabolism. This study provides valuable information to improve hypoxia-tolerance of grass carp.     

Effect of dietary garlic supplementation on lipid peroxidation and protein oxidation biomarkers of tissues as well as some serum biochemical parameters in common carp Cyprinus carpio

This study aims to investigate the effects of dietary garlic powder (25 and 50 g kg^?1 feed) supplementation for 6 weeks on lipid and protein oxidation biomarkers in various tissues as well as some blood biochemical parameters in common carp. Based on the present study results, serum malondialdehyde (MDA) concentrations were decreased following garlic supplementation, but the decrease was only significant (P < 0.05) in the group that received 50 g kg^?1 dietary garlic compared with the control group. Moreover, garlic at 50 g kg^?1 diet caused significant decrease in MDA values of liver and kidney. Additionally, the decreasing effect of garlic at 25 g kg^?1 diet on MDA values was only significant in liver. Protein carbonyl contents were only decreased significantly in muscle following garlic administration at 25 g kg^?1 diet. Serum aspartate aminotransferase activity decreased significantly in carp that received 25 g kg^?1 dietary garlic. Moreover, alkaline phosphatase activity decreased significantly in carp fed diets containing 25 and 50 g kg^?1 garlic. On the other hand, garlic supplementation had no significant effect on gamma-glutamyl transferase activity and total protein, albumin, and creatinine concentrations. The results of the present study indicate that garlic powder has potential to decrease oxidative stress to some extent by reducing lipid and protein oxidation in some tissues of common carp.     

Effect of dietary lysine on growth,intestinal enzymes activities and antioxidant status of sub-adult grass carp (Ctenopharyngodon idella)

The dietary lysine requirement of sub-adult grass carp (460 ± 1.5 g) was assessed by feeding diets supplemented with grade levels of lysine (6.6, 8.5, 10.8, 12.9, 15.0 and 16.7 g kg^?1 diet) for 56 days. The test diets (28 % CP) contained fish meal, casein and gelatin as sources of intact protein, supplemented with crystalline amino acids. Weight gain (WG), feed intake and feed efficiency were significantly improved with increasing levels of lysine up to 12.9 g kg^?1 diet and thereafter declined (P < 0.05). Quadratic regression analysis of WG at 95 % maximum response indicated lysine requirement was 10.9 g kg^?1 diet. Activities of trypsin, chymotrypsin, lipase, Na⁺, K⁺-ATPase and alkaline phosphatase in intestine, creatine kinase activity in proximal and mid-intestine responded similar to WG (P < 0.05). In addition, lipid and protein oxidation decreased with increasing levels of lysine up to certain values and increased thereafter (P < 0.05); the anti-hydroxyl radical capacity, dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase (GST) activities and glutathione content were increased with increasing dietary lysine levels up to certain values in the detected tissues, except for hepatopancreatic GST. Requirement estimated on the basis of malondialdehyde content in intestine and hepatopancreas was 10.6 and 9.53 g lysine kg^?1 diet, respectively.     

Effect of prebiotic konjac mannanoligosaccharide on growth performances,intestinal microflora,and digestive enzyme activities in yellow catfish,Pelteobagrus fulvidraco

In the present study, konjac mannanoligosaccharide (KMOS) was evaluated as a prebiotic in yellow catfish. The fish were fed with diets containing KMOS in four concentrations: 0 g kg^?1 (C), 1.0 g kg^?1 (KM1), 2.0 g kg^?1 (KM2), and 3.0 g kg^?1 (KM3) for 49 days, respectively. Another group fed with diets containing 3.0 g kg^?1 yeast cell wall mannanoligosaccharide (MOS) (M3) was set as positive control. The results indicated that fish receiving the diets supplemented with KMOS or MOS showed higher relative gain rate (RGR), specific growth rate (SGR), and lower feed conversion ratio (FCR) with significantly differences (P < 0.05) than those fed with the basal diets. Moreover, fish receiving the diets with 2.0 g kg^?1 KMOS inclusion showed higher RGR, SGR, and lower FCR (P < 0.05) than that feeding the diets supplemented with 3.0 g kg^?1 MOS. The quantities of Bifidobacterium spp. were significantly increased (P < 0.05). Meanwhile, Escherichia coli and Aeromonas spp. were significantly reduced (P < 0.05) in the fish-feeding diets with 2.0 g kg^?1 KMOS supplement. Compared with the control group, the significantly enhancement of protease and amylase activity (P < 0.05) in intestine and pancreas was observed in fish fed with diets containing KMOS or MOS. Collectively, an optimum level of KMOS inclusion in diets could modulate intestinal microflora, induce digestive enzyme activity, and improve the growth performance of yellow catfish significantly.     

Transferability of oxytetracycline (OTC) from feed to carp muscle and evaluation of the antibiotic effects on antioxidant systems in liver and kidney

Oxytetracycline (OTC) is employed in fish farms to contest or prevent bacterial infections. We simulated an OTC treatment at therapeutic level (75 mg kg^?1) and at higher doses (150, 300 mg kg^?1) for 10 days. A withdrawal period of 10 days was considered for treated carp, carrying out the same chemical and biochemical analyses (total glutathione, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase and malondialdehyde). The aim was to obtain data related to the carryover in muscle and on variations in the antioxidant indicators in liver and kidney. The OTC residual levels in muscle showed a dose–response relationship. After 10 days of treatment at the recommended dose (75 mg kg^?1), the mean value in muscle was 295 μg kg^?1. After 10 withdrawal days, residues in all treated groups were not entirely eliminated by fish. Residues of recommended 75 mg kg^?1 OTC dose were lower than the maximum permitted by EEC regulation: 100 μg kg^?1. Disturbance in the antioxidant systems in liver and kidney was recorded in (150, 300 mg kg^?1) carp, as well as during the withdrawal period. A lowered superoxide dismutase activity and higher levels of catalase, glutathione peroxidase, glutathione reductase and glutathione were evaluated in liver, while in kidney only higher malondialdehyde and glutathione S-transferase concentrations were recorded for 300 mg kg^?1 dose. The therapeutic OTC dose exerted lower effects, and only in liver, enhancement of GPx and GR activities was recorded. After the withdrawal period, altered antioxidant responses in tissues were restored for all three OTC doses.     

Protective effects of basil (Ocimum basilicum) ethanolic extract supplementation diets against experimental Aeromonas hydrophila infection in common carp (Cyprinus carpio)

This study evaluated the effects of basil (Ocimum basilicum) leaves extract supplement on growth, blood parameters and resistance to Aeromonas hydrophila in Cyprinus carpio fingerlings. Basil leaves were mixed thoroughly with feed at 0, 100, 200, 400, 800 and 1600 mg kg^?1 of diet and were fed in triplicate group for 2 months. At the end of this period, growth performance and survival were determined. Then fish were challenged intraperitoneally with A. hydrophila and mortalities were recorded up to 10 days post challenge. Results indicated that WBC, RBC, Ht, Hb, total protein, albumin and globulin were higher (P < 0.05) in fish fed diets containing O. basilicum compared with the control. Highest specific growth rate values were observed in 400 mg kg^?1 group. Feed conversion ratio was significantly lower (P < 0.05) in fingerlings fed 400 and 800 mg O. basilicum kg^?1 dry diet. After 10 days post challenge, total protein, WBC, RBC and Hb were significantly higher in 400 mg kg^?1 compared with other groups. These results reveal that a dietary O. basilicum leaves extract of 400 mg kg^?1 fed for 60 days leads to increased growth performance and survival rate as well as improved feeding efficiency in common carp fingerlings rendering them more resistant against infection by A. hydrophila.     

Effects of practical dietary protein to lipid levels on growth,digestive enzyme activities and body composition of juvenile rice field eel (Monopterus albus)

A 10-week feeding experiment was conducted to evaluate the effects of dietary protein to lipid ratios (P/L) on growth, intestinal digestive enzyme activities and body composition in juvenile rice field eel (Monopterus albus) (initial mean body weight of 65.76 ± 1.07 g, mean ± SEM). Nine test diets were formulated in a 3 × 3 factorial design to contain three protein levels (350, 400 and 450 g kg^?1) for each of three lipid levels (40, 80 and 120 g kg^?1), respectively. Each diet was randomly assigned to triplicate groups of 60 fish per net cage (1.5 × 2.0 × 1.5 m). Results showed the survival was above 96 % and was not affected by dietary treatments. Fish fed the diet with 450 g kg^?1 protein and 40 g kg^?1 lipid showed the best weight gain (WG) (103.95 %) and feed conversion ratio (1.60) (P < 0.05). WG, protein efficiency ratio and energy retention increased with the increasing in lipid at 350 g kg^?1 protein level (P < 0.05). However, WG showed a little decline with increasing dietary lipid when fish fed the diets with 400 and 450 g kg^?1 protein level, but no significant difference was observed (P < 0.05). Hepatosomatic index, visceralsomatic index and intestinal lipase activity increased with the increasing of dietary lipid level irrespective protein level. Intestinal trypsin activity increased with the increasing of dietary lipid level when fish fed the diets with 350 g kg^?1 protein, but showed converse trend when fish fed the diets with 400 and 450 g kg^?1 protein. Serum triglyceride, body lipid and energy were positively correlated with the dietary lipid. Results of the present study showed that the dietary protein/lipid ratio of 450/40 g kg^?1 is considered optimum for rice field eel under culture conditions, and the increase in dietary lipid level has no efficient protein-sparing effect when fish fed the diets with 400 and 450 g kg^?1 protein level.     

Plasma biochemical responses of the omnivorous crucian carp (<Emphasis Type="Italic">Carassius auratus</Emphasis>) to crude cyanobacterial extracts

Healthy crucian carp (Carassius auratus) were treated by intraperitoneal (i.p.) injection of crude cyanobacterial extracts at two doses, 50 and 200 μg MC-LR equiv kg⁻¹ BW. High mortality (100%) was observed within 60 h post injection in the high-dose group. In the treated fish, activities of four plasma enzymes, alanine aminotransferase (ALT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH), all showed substantial increases, with both dose and time-dependent effects. These increases of enzyme activity indicate severe impairment occurred in the liver of crucian carp over time. Plasma concentrations of energy-related biomolecules including glucose (GLU), cholesterol (CHO), triglyceride (TG), and total protein (TP) showed marked changes in the high-dose group, possibly a nutritional imbalance correlated with the liver injury caused by intraperitoneal exposure to crude cyanobacterial extracts.     

Effect of dietary graded levels of cottonseed meal and gossypol on growth performance,body composition and health aspects of allogynogenetic silver crucian carp,Carassius auratus gibelio♀ × Cyprinus carpio♂

A 6‐month trial was conducted to evaluate the effects of dietary cottonseed meal (CSM) and free gossypol (FG) on allogynogenetic silver crucian carp, Carassius auratus gibelio♀ × Cyprinus carpio♂ with 4 replicates of each treatment. Isonitrogenous and isocaloric diets were formulated with the 0 g kg^?1 (control), 200 g kg^?1, 400 g kg^?1, and 560 g kg^?1 CSM. Diets with FG were made by supplementing batches of control diet with 214 mg kg^?1, 428 mg kg^?1, and 642 mg kg^?1. Weight gain, specific growth rate, and protein efficiency ratio increased significantly up to an inclusion level of CSM of 400 g kg^?1 in the diet, with a significant decrease in food conversion ratio. Further increase in CSM to 560 g kg^?1 did not cause further changes in fish performance. Free gossypol did not affect fish performance significantly at any inclusion level. Neither CSM nor FG caused significant effects in any of the other evaluated parameters such as whole body composition, haemoglobin concentration, activities of serum lysozyme, superoxide dismutase, alanine aminotransferase and aspartate aminotransferase, and histology of hepatic tissues and midgut. Our results suggested that crucian carp can tolerate at least 642 mg kg^?1 FG and that it is safe to including 400 g kg^?1 CSM in crucian carp feed.     

Modulation of appetite,lipid and glucose metabolism of juvenile grass carp (<Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>) by different dietary protein levels

This study was undertaken to explore the systemic metabolic strategies of juvenile grass carp (Ctenopharyngodon idellus) to maintain growth when fed with different dietary protein levels. The optimal growth group and two growing discomfort groups were selected through the basic data, to explain the growth difference from appetite regulation and lipid and glucose metabolism perspective. Three experimental diets were formulated with three dietary protein levels at 200.3, 296.1 and 442.9 g kg^?1, named P1, P2 and P3, respectively. Juvenile grass carp (initial body weight 12.28 ± 0.14 g) were fed with three diets with 3 replications per dietary treatment in an indoor recirculation system for an 8-week feeding trial. Fish fed with diet P2 dietary group showed significantly higher WG, SGR, FI and PER than other groups. Compared with other groups, mRNA expressions of NPY, Y8a and Y8b in fish fed with P2 significantly down-regulated, while the expressions of CCK and CART in fish fed with P3 significantly down-regulated (P < 0.05). With increasing dietary protein levels, G6Pase, GK, PK and PEPCK were all significantly inhibited (P < 0.05). For lipid metabolism, the mRNA expression of ACC in P1 dietary group was significantly higher than P3 dietary group; besides, LPL expression in P3 group was significantly higher than other two groups (P < 0.05). PPARα expression in P2 was significantly lower than other groups (P < 0.05). These results suggested that grass carp fed with P2 (296.1 g kg^?1 protein level) showed highest weight gain, contributed to more balanced nutrient metabolism and appetite regulation. Too high dietary protein (442.9 g kg^?1) should be avoided because it induced lowest PER, body lipid and liver lipid, and inhibited glucose and lipid metabolism in juvenile grass carp.     

Effects of dietary cholesterol supplementation on growth and cholesterol metabolism of rainbow trout (Oncorhynchus mykiss) fed diets with cottonseed meal or rapeseed meal

This study was conducted to evaluate the effects of cholesterol on growth and cholesterol metabolism of rainbow trout (Oncorhynchus mykiss) fed diets with cottonseed meal (CSM) or rapeseed meal (RSM). Four experimental diets were formulated to contain 550 g kg^?1 CSM or 450 g kg^?1 RSM with or without 9 g kg^?1 supplemental cholesterol. Growth rate and feed utilization efficiency of fish fed diets with 450 g kg^?1 RSM were inferior to fish fed diets with 550 g kg^?1 CSM regardless of cholesterol level. Dietary cholesterol supplementation increased the growth rate of fish fed diets with RSM, and growth rate and feed utilization efficiency of fish fed diets with CSM. Similarly, dietary cholesterol supplementation increased the plasma total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triiodothyronine levels, but decreased the plasma triglycerides and cortisol levels of fish fed diets with RSM or CSM. In addition, supplemental cholesterol increased the free cholesterol and TC levels in intestinal contents, but decreased the hepatic 3-hydroxy-3-methyl-glutaryl-CoA reductase activity of fish fed diets with RSM or CSM. These results indicate that 9 g kg^?1 cholesterol supplementation seems to improve the growth of rainbow trout fed diets with CSM or RSM, and the growth-promoting action may be related to the alleviation of the negative effects caused by antinutritional factors and/or make up for the deficiency of endogenous cholesterol in rainbow trout.     

Immunogene expression in head kidney and spleen of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) following thermal stress and challenge with Gram-negative bacterium, <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

To evaluate the effect of thermal and microbial stress on the immune response of common carp (Cyprinus carpio L.), relative mRNA expression level of pro-inflammatory cytokines [tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1β] and other genes related to immune or stress response [inducible nitric oxide synthase (iNOS), heat shock protein 70 (Hsp70), superoxide dismutase one (SOD1), and glucocorticoid receptor (GR)] was measured by quantitative PCR (qPCR). In addition, total protein and total immunoglobulin level in blood plasma of experimental common carp was also assayed. All the above parameters were estimated 24 h post-challenge with Gram-negative bacterium, Aeromonas hydrophila. Common carp (54.89?±?6.90 g) were initially exposed to 20 °C (control group) and 30 °C (thermal stress group) water temperature for 30 days, followed by experimental challenge with 2.29?×?10⁸ colony forming unit/mL (CFU/mL; LD₅₀ dose) of A. hydrophila. Exposure of fish to thermal stress and subsequently challenge with A. hydrophila significantly (P?<?0.05) increases the IL-1β mRNA expression in head kidney and spleen of common carp by ~?39.94 and ~?4.11-fold, respectively. However, TNF-α mRNA expression in spleen decreased ~?5.63-fold in control fish challenged with A. hydrophila. Thermal stress and challenge with bacterium suppresses the iNOS and GR mRNA expression in spleen of common carp. Moreover, significant (P?<?0.05) increase in total protein content of blood plasma (~?43 mg/g) was evident in fish exposed to thermal stress and challenged with A. hydrophila. In conclusion, our study highlights the importance of elevated temperature stress and microbial infection in differential regulation of expression of several immunogenes in common carp.     

Dietary protein and carbohydrate requirement of juvenile Hawaiian limpet (<Emphasis Type="Italic">Cellana sandwicensis</Emphasis> Pease, 1861) fed practical diet

This study was conducted to evaluate dietary protein and carbohydrate requirement of juvenile Hawaiian limpets Cellana sandwincensis. A total of 64 juvenile limpets (3.12 ± 0.86 g) were fed five different dietary protein levels ranging from 270 to 470 g kg^?1 for 90 days. Carbohydrate and lipid levels were held constant at 180 and 49.7 g kg^?1, respectively. Weight gain and growth rates of the animals did not differ significantly (P > 0.05) among the protein levels ranging from 270 g kg^?1 (0.30 % day^?1) to 470 g kg^?1 (0.23 % day^?1). Next, opihi were fed four diets with protein levels from 210 to 500 g kg^?1 with a constant carbohydrate level at 120 g kg^?1. Weight gain and specific growth rates of opihi increased with increasing dietary protein from 210 to 350 g kg^?1, and significantly (P < 0.05) decreased at the 500 g kg^?1 diet. Highest weight gain, growth rates, and protein efficiency ratio were achieved at 350 g kg^?1. Elevated carbohydrate levels (180–370 g kg^?1) produced a significant difference (P < 0.05) in growth. The fastest growth rates of animals were obtained with 270 g kg^?1 (0.27 % day^?1) and 320 g kg^?1 (0.26 % day^?1). The weight gain of animals fed 180 and 370 g kg^?1 carbohydrate diets were significantly (P < 0.05) lower than those of animals fed 270 and 320 g kg^?1. We conclude that about 350 g kg^?1 protein and 320 g kg^?1 carbohydrate levels could be used for opihi.     

Dietary lipid concentrations influence growth,liver oxidative stress,and serum metabolites of juvenile hybrid snakehead (<Emphasis Type="Italic">Channa argus</Emphasis> × <Emphasis Type="Italic">Channa maculata</Emphasis>)

The study was conducted to evaluate the effect of dietary lipid levels on growth, liver oxidative stress, and serum metabolites of juvenile hybrid snakehead (Channa argus × Channa maculata). Five isonitrogenous (crude protein 420 g kg^?1) practical diets containing 58, 87, 115, 144, and 173 g kg^?1 crude lipid (named L58, L87, L115, L144, and L173, respectively) were fed to triplicate groups of 30 fish (mean initial weight 24 g) for 8 weeks. The results showed that the final body weight (58.68–78.81 g), specific growth rate (1.41–1.75 % day^?1), and protein efficiency ratio (1.66–2.64) increased significantly with the increasing dietary lipid levels. Liver lipid contents (71.65–101.80 g kg^?1) and crude lipid (52.10–83.63 g kg^?1) of whole body increased with increasing dietary lipid levels and reached the highest values in fish of L173. Fish of L173 showed lower alkaline phosphatase (23.81 King Unit gprot^?1) and catalase activities (4.44 U mgprot^?1) but higher malondialdehyde content (0.69 nmol mgprot^?1) in liver than the other groups. Higher alanine transaminase activity (8.20 U L^?1), aspartate transaminase activity (63.65 U L^?1), and triglyceride (0.29 mmol L^?1) in serum were observed in fish of L173 compared to the other treatments. Fish of L144 showed higher superoxide dismutase activity and glutathione peroxidase activities in liver than that of fish fed diet L58. Fish fed diet L58 showed lower total cholesterol (3.61 mmol L^?1), high-density lipoprotein cholesterol (1.39 mmol L^?1), and low-density lipoprotein cholesterol (0.46 mmol L^?1) in serum. These results suggested that juvenile snakehead (Channa argus × Channa maculata) achieved good growth performance with dietary lipid level 173 g kg^?1. Diet with 143 g kg^?1 lipid was more conductive to liver health. The appropriate dietary lipid supplementation needs to be determined in further studies.     

Effects of replacing fish meal with rubber seed meal on growth,nutrient utilization,and cholesterol metabolism of tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis> × <Emphasis Type="Italic">O. aureus</Emphasis>)

A feeding trial was conducted to evaluate the effects of replacing fish meal with rubber seed meal (RSM) on growth, nutrient utilization, and cholesterol metabolism of tilapia (Oreochromis niloticus × Oreochromis aureus). Five experimental diets were formulated with 0, 150, 300, 450, and 600 g kg^?1 RSM replacing graded levels of fish meal, respectively. Each diet was randomly assigned to triplicate groups of 25 fish (initial average weight 65.3 g) per aquarium in a rearing system maintained at 29 ± 1 °C for 8 weeks. Dietary 150 g kg^?1 RSM inclusion did not affect the weight gain and daily growth coefficient, whereas these were depressed by a further inclusion. Additionally, feed efficiency ratio and protein efficiency ratio were not affected by dietary RSM inclusion regardless of inclusion level. However, the inclusion of 450 and 600 g kg^?1 RSM decreased the mid-intestinal trypsin, lipase, and amylase activities; the hepatic acyl-CoA/cholesterol acyl transferase; low-density lipoprotein receptor; and 3-hydroxy-3-methyl-glutaryl-CoA reductase activities. Similarly, dietary 600 g kg^?1 RSM inclusion inhibited the plasma catalase and hepatic glutathione peroxidase activities. These results indicated that 150 g kg^?1 RSM can be included in tilapia diets, whereas higher inclusion of RSM inhibited the growth rate, digestive enzyme activity, antioxidant capacity, and cholesterol metabolism.     

Growth performance and bone mineralization of large Nile tilapia (Oreochromis niloticus) fed graded levels of available phosphorus

The effect of graded levels of dietary available phosphorus (AP) on large Nile tilapia (145.87 ± 9.51 g) performance, feed efficiency, body composition and mineral retention in vertebrae was evaluated. All male fish were distributed into three replicates in fiberglass aquaria (800 L each; 12 fish per tank) for 87 days and hand fed to pelletized diets three times a day until apparent satiation. Diets with approximately 302 g kg^?1 of digestible protein and 15.2 kJ g^?1 of digestible energy with graded levels of dibasic phosphate yield AP levels of 2.39, 4.17, 6.12 and 8.91 g kg^?1. At the end of the trial, feed intake, hepatosomatic index, fillet yield, whole body moisture and crude protein of fish fed 2.39–8.91 g kg^?1 of AP diets were not significantly different. The supplementation of 6.12 and 8.91 g kg^?1 of AP resulted in significantly increased weight gain, whole body ash and calcium. Whole body crude lipids significantly decreased with increasing AP from 6.12 to 8.91 g kg^?1. However, concentration of zinc in the vertebrae was not affected by dietary treatments. The magnesium contents of the fish vertebrae were lower in fish fed lower dietary AP level. No effects of the dietary AP on apparent digestibility coefficients of energy and nutrients were observed. The study indicated that the dietary AP level of at least 6.12 g kg^?1 satisfies the needs for growth performance, body composition and bone mineralization of large Nile tilapia.     

Quantitative dietary isoleucine requirement of juvenile Pacific white shrimp,Litopenaeus vannamei (Boone) reared in low-salinity water

This study was designed to determine the isoleucine requirement of juvenile Pacific white shrimp Litopenaeus vannamei (Boone) in low-salinity water (0.50–0.70 g L^?1). Six diets were formulated to contain 410 g kg^?1 crude protein with fish meal, peanut meal and pre-coated crystalline amino acids with different concentration of l-isoleucine (9.35, 11.85, 14.35, 16.85, 19.35, and 21.85 g kg^?1 dry diet, defined as diet I1, diet I2, diet I3, diet I4, diet I5 and diet I6, respectively.). Each diet was randomly assigned to triplicate treatments of 30 shrimps (0.43 ± 0.005 g), and the feed trial lasted for 8 weeks. The results indicated that the weight gain significantly increased with increasing isoleucine concentration up to 14.35 g kg^?1 (diet I3), whereas it was reduced in the treatments exceeding 16.85 g kg^?1 isoleucine (diet I4) significantly (P < 0.05). Moreover, the highest body protein deposition and protein efficiency ratio, and the lowest feed conversion ratio, haemolymph aspartate aminotransferase and alanine aminotransferase activities were also found at treatment I3–I4 (P < 0.05). And the haemolymph urea nitrogen concentration of shrimps-fed diet I6 was particularly higher than those fed with diets I1–I5 (P < 0.05). The results of polynomial regression based on weight gain, feed efficiency and body protein deposition indicated that the optimal dietary isoleucine requirement for L. vannamei reared in low-salinity water was 15.95 g kg^?1 isoleucine of dry diet, correspondingly 38.81 g kg^?1 of dietary protein.     

Effects of graded levels of dietary myo‐inositol on non‐specific immune and specific immune parameters in juvenile Jian carp (Cyprinus carpio var. Jian)

The aim of this study was to evaluate the effects of myo‐inositol (MI) on non‐specific immune and specific immune defence in fish. A total of 1050 Jian carp (Cyprinus carpio var. Jian) (22.28±0.07 g) were randomly distributed into seven groups, of three replicates each, of feeding diets containing graded levels of MI (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg MI kg^?1 diet). After a 60‐day growth trial, an infectious trial was conducted by injection of Aeromonas hydrophila for 17 days. Results showed that the red blood cell (RBC) and the white blood cell count were significantly increased with increasing MI levels up to 535.8 mg kg^?1 diet (P<0.05). The spleen index showed a tendency similar to RBC, whereas the head kidney index showed the inverse pattern (P<0.05). The phagocytic activity of leucocytes, haemagglutination titre, lysozyme activity, anti‐A. hydrophila antibody titre and immunoglobulin M, after being injected with A. hydrophila, were all improved with an increase in the MI levels up to 232.7–687.3 mg kg^?1 diet respectively (P<0.05). Myo‐inositol did not influence serum acid phosphatase activity and total iron‐binding capacity (P>0.05). These results suggested that MI could enhance non‐specific immune and specific immune responses in fish.