Efficacy and effects of clove oil and MS‐222 on the immune‐biochemical responses of juvenile rohu Labeo rohita

The present study determined the effective concentrations of clove oil and MS‐222 in juvenile rohu Labeo rohita for quick induction and recovery. The immune‐biochemical responses due to 0, 1 and 24 hr exposure to those anaesthetics were also evaluated. Of four concentrations of the anaesthetics examined, the lowest effective concentration of clove oil and MS‐222 were 50 µl/L and 125 mg/L respectively. Clove oil and MS‐222 significantly increased the myeloperoxidase, total protein and alkaline phosphatase activity at some of the holding durations. However, superoxide anion production (after 0 and 1 hr) and antiprotease activity (after 24 hr) were significantly reduced in fish exposed to clove oil. Serum glucose content was significantly elevated in the MS‐222‐treated group. Furthermore, the clove oil‐treated group showed significantly higher levels of serum Na⁺ and K⁺, while the aspartate and alanine aminotransferase activities were significantly enhanced in the MS‐222 group. The use of both clove oil and MS‐222 is advised as an anaesthetic agent for rohu with a bias towards clove oil, considering its economic and operational feasibility.     

Pre‐challenge and post‐challenge haemato‐immunological changes in Oreochromis niloticus (Linnaeus, 1758) fed argan oil against Lactococcus garvieae

The present study investigated the effects of argan oil, obtained from Argania spinosa, on pre‐ and post‐challenge immuno‐haematological and biochemical responses of Nile tilapia, Oreochromis niloticus. For this purpose, the fish were fed diets containing 0, 0.5%, 1% or 2% argan oil for 45 days. Following 45 days of feeding, fish were challenged with Lactococcus garvieae and mortality was recorded for 15 days. During the pre‐challenge period, significantly higher respiratory burst activity, total white blood cell (WBC), serum lysozyme activity and myeloperoxidase activity were determined in the argan oil‐fed groups. The serum glucose and cholesterol levels decreased whilst total protein and albumin did not change in the groups fed with argan oil‐supplemented diets. After challenge with Lactococcus garvieae, the percentage survival (%) was found to be the highest in the 1% and 2% argan oil‐supplemented feeding groups. Also, there was a significant increase in weight gain, specific growth rate and feed conversion ratio in those fish fed argan oil. The results of this study indicated that after the supplementation of fish diets with argan oil, especially at 1% and 2% concentrations, the immunological, haematological and biochemical values remained similar in both the pre‐ and post‐challenge periods and the immune response against L. garvieae in Nile tilapia was modulated.     

The optimal dietary protein level of large‐size grouper Epinephelus coioides

An 8‐week feeding trial was conducted to determine the requirement of protein for large‐size grouper Epinephelus coioides (initial body weight: 275.07 ± 1.56 g). Six iso‐lipidic (124 g/kg) diets were formulated containing graded levels of protein (350, 400, 450, 500, 550 and 600 g/kg). Grouper was hand‐fed twice daily to apparent satiation with triplicate. The results showed that significantly high weight gain, specific growth rate and significantly low feed conversion ratio were observed in fish fed 450 g/kg protein group. High‐protein level diets significantly increased protein content and significantly decreased lipid content of fish body and muscle. Total protein and cholesterol content in serum of 600 g/kg group were significantly higher than those of 350 g/kg group. However, serum glucose and triglyceride contents of fish fed low‐protein diets were significantly higher than those of fish fed high‐protein diets. Meanwhile, liver glutamic‐pyruvic transaminase and glutamic‐oxaloacetic transaminase in high‐protein diet groups were significantly higher than those of low‐protein diet groups. The intestinal protease activity in high‐protein diet groups was significantly higher that of low‐protein diet groups, but lipase and amylase showed opposite trend. With the increasing of dietary protein level, the activities of alkaline phosphatase, superoxide dismutase and lysozyme in liver of grouper increased significantly compared with 350 g/kg group, while the activities of acid phosphatase decreased significantly. With specific growth rate as the evaluation index, the optimum dietary protein level of large‐size grouper Epinephelus coioides was 438.39 g/kg by fitting the broken‐line regression analysis.     

Dietary astaxanthin differentially affected the lipid accumulation in the liver and muscle of the marine teleost,tiger puffer Takifugu rubripes

The lipid‐regulating effects of astaxanthin (ASTX) have been widely reported in terrestrial animals. However, little relevant information has been available in fish although ASTX has been used as exogenous pigment and antioxidant in fish feed. A 74‐day feeding study was conducted to investigate the effects of dietary ASTX on lipid accumulation in the marine teleost tiger puffer. Four experimental diets differing only in ASTX supplementation, that is, 0 (control), 50 (ASTX50), 100 (ASTX100) and 500 (ASTX500) mg kg^‐1, were randomly assigned to 12 tanks of juvenile tiger puffer. Compared to control, the liver lipid content in group ASTX50 was significantly higher, while those in groups ASTX100 and ASTX500 were lower. The muscle lipid contents in group ASTX500 were significantly higher compared to control. Group ASTX50 had the best growth performances, while diet ASTX500 seemed to have adverse effects. In the liver, compared to control, groups ASTX50 and ASTX100 showed significantly lower mRNA expressions of genes related to triglycerol synthesis and fatty acid synthesis, transport and uptake, but higher expressions of genes related to β‐oxidation and monoglycerol hydrolysis. In the muscle, compared to control, ASTX100 showed higher expressions of genes related to β‐oxidation. ASTX50 resulted in higher contents of saturated and monounsaturated fatty acids but lower contents of n‐3 polyunsaturated fatty acids in fish. In conclusion, astaxanthin in diets for tiger puffer differentially regulated the lipid accumulation in the liver and muscle, both in dose‐dependent manners. Excess dietary astaxanthin (500 mg/kg) had adverse effects on tiger puffer.     

Effects of dietary linolenic acid on growth,fatty acid composition,immune function and antioxidant status of juvenile blunt snout bream,Megalobrama amblycephala

A nine‐week feeding trial was performed to determine the dietary linolenic acid (LNA; 18:3n–3) requirements of juvenile blunt snout bream. Six iso‐nitrogenous, semi‐purified diets were prepared with different concentrations of LNA (0–25 g/kg). Dietary LNA had no significant effects on survival rate. However, final fish weight, weight gain (WG), specific growth rate (SGR) and feed efficiency ratio (FER) increased with increasing dietary LNA concentrations up to 20 g/kg. Dietary LNA increased muscle LNA and total n‐3 polyunsaturated fatty acid (PUFA) contents, but decreased total saturated fatty acid content. Fish fed 20 g/kg LNA had the highest plasma alkaline phosphatase activity, total protein, albumin and white blood cell count levels. Additionally, fish fed 20 g/kg LNA had higher triglyceride levels than control fish. Plasma glucose increased with increasing dietary LNA concentrations. Superoxide dismutase and glutathione peroxidase activities significantly increased with increasing dietary LNA concentrations up to 15 g/kg. Based on SGR and FER, the optimal dietary LNA requirements of juvenile blunt snout bream were 17.5 and 15.6 g/kg respectively.     

Influence of nanochitosan/zeolite composite on growth performance,digestive enzymes and serum biochemical parameters in rainbow trout (Oncorhynchus mykiss)

Protective effects of nanochitosan/zeolite composite besides zeolite and chitosan/zeolite composite on rainbow trout growth, digestive enzyme activities and biochemical parameters were studied. Nanochitosan/zeolite hybrid composites with three different ratio of nanochitosan:zeolite (35:100, 3.5:100 and 0.35:100) were synthesized and analysed by X‐ray powder diffraction (XRD), thermal gravim (TG) analysis and scanning electron microscope (SEM) methods. Prepared composites as well as zeolite and control diets were fed to rainbow trout (50 g) for a period of 60 days. The addition of treated diets significantly improved growth performance compared to the control diet. Supplemental zeolite could only enhance the amylase activity in fish intestine, whereas other treatment groups could increase the pepsin activity besides intestinal alkaline phosphatase, trypsin and amylase activities. No differences were observed for intestinal acid phosphatase and lipase activities among the experimental diets. Meanwhile, serum total antioxidant activity and lipid peroxidation product, indicated by malondialdehyde (MDA), significantly increased and decreased, respectively, with some doses of administration, indicating the elevated antioxidant status in treatment groups. Serum‐specific marker enzymes, namely aspartate aminotransferase (AST) and alkaline phosphatase (ALP), were not affected in all groups. Meanwhile serum total protein in most treatment groups was significantly higher than the control group. Results showed that synthesized composites especially nanochitosan/zeolite composite at 5 g/kg had potential to enhance growth performance, digestive enzyme activities and some biochemical parameters in rainbow trout.     

Effects of Dietary Vitamin C on Blood Chemistry and Nonspecific Immune Response of Juvenile Red Sea Bream,Pagrus major

A trial was conducted to determine the effect of ascorbyl‐2‐monophosphate Na/Ca (AMP‐Na/Ca) on blood chemistry and nonspecific immune response of red sea bream juveniles. Test diets with three levels of AsA (free, 107, and 325 mg/kg diet) were fed to juvenile red sea bream (36.0 ± 1.3 g) two times a day for 3 wk. There were no significant differences in hematocrit, glucose, and blood urea nitrogen. Total cholesterol and triglyceride in plasma of fish fed AsA‐free diet was significantly (P < 0.05) higher than that of fish fed two other diets. There were no significant differences in serum albumin, total bilirubin, and total serum protein. Glutamyl oxaloacetic transaminase in serum of fish fed diets containing 107 and 325 mg of AsA were significantly (P < 0.05) lower than that of fish fed AsA‐free diet. Serum lysozyme activity (LA) of fish fed diets containing 107 and 325 mg of AsA were significantly (P < 0.05) higher than that of fish fed AsA‐free diet. There was no significant difference in mucus LA. The results mentioned above demonstrated that AMP‐Na/Ca is a bioavailable AsA source for red sea bream juveniles. Supplement of more than 107 mg AsA/kg in diets improved blood chemistry and nonspecific immune function of red sea bream juveniles.     

Indexing serum biochemical attributes of Lutjanus argentimaculatus (Forsskal, 1775) to instrument in health assessment

The present study was aimed to establish reference data for nine serum biochemical attributes (glucose, protein, albumin, globulin, albumin/globulin ratio, cholesterol, triglycerides, serum glutamate oxaloacetate transaminase [SGOT] and serum glutamate pyruvate transaminase [SGPT]) of a supreme aquaculture candidate, namely Lutjanus argentimaculatus. Further, the influence of ecotype (cage–wild), condition index and gender on biochemical attributes was evaluated. The results have shown that gender and condition index had no significant effect in the studied age group, whereas ecotype had a significant role, except on serum glucose levels, suggesting the prime importance of estimating ecotype‐specific reference intervals for interpreting fish health. Intra‐ecotype variability of serum biochemical attributes, namely serum protein, globulin, cholesterol and triglycerides, was less, suggesting the possibility of using these parameters as health indices within a specific ecotype. Consistency in terms of the least intra‐ecotype variability coupled with PCA results points serum protein as the best ecotype‐specific health index among the different parameters studied. Altogether, the results of the present study provide thought‐provoking insights on serum biochemistry of L. argentimaculatus as a platform for the health management of this supreme aquaculture candidate.     

饲料中糖/脂肪比对暗纹东方鲀幼鱼生长、血液指标、肝代谢酶活性及PEPCK基因表达的影响

配制6种不同糖/脂肪比例（CHO∶L分别为4.29、2.79、1.86、1.19、0.73和0.41）的等氮等能饲料,饲养暗纹东方鲀幼鱼[初始体重为(11.2 ± 0.5) g] 60 d,探讨饲料中糖与脂肪比例对其生长、饲料利用、生理生化指标和PEPCK基因表达的影响。试验结果表明：随饲料中CHO∶L降低,暗纹东方鲀特定生长率（SGR）、蛋白质效率（PER）和饲料效率（FE）先升高后降低,且均在CHO∶L为1.86时达最大,显著高于CHO∶L为0.41、0.73和4.29时的值(P<0.05)。血浆甘油三酯和肝脏脂肪含量随CHO∶L降低而显著增加(P<0.05),而血糖和肝糖原含量随CHO∶L降低而显著降低(P<0.05)。随饲料中CHO∶L降低,肝脏脂肪酶和脂肪合成酶活性先增加后降低,分别在CHO∶L为1.19和1.86时活性最高。CHO∶L为1.86-4.29时PK活性显著高于其他饲料组(P<0.05)。CHO：L为0.41和0.73时,AMS活性显著低于其他饲料组(P<0.05),而PEPCK活性和mRNA相对表达量显著高于其他饲料组(P<0.05)。饲料中CHO∶L对暗纹东方鲀存活率和血浆总胆固醇含量无显著影响(P>0.05)。分别用二次多项回归模型拟合SGR、PER、FE和CHO∶L的关系,得到暗纹东方鲀幼鱼饲料中CHO∶L的适宜范围为2.01~2.16,且其对碳水化合物的利用能力要高于脂肪。     

Effects of dietary amylose/amylopectin ratio on growth performance,feed utilization,digestive enzymes,and postprandial metabolic responses in juvenile obscure puffer Takifugu obscurus

The effect of dietary amylose/amylopectin (AM/AP) ratio on growth, feed utilization, digestive enzyme activities, plasma parameters, and postprandial blood glucose responses was evaluated in juvenile obscure puffer, Takifugu obscurus. Five isonitrogenous (430 g kg^?1 crude protein) and isolipidic (90 g kg^?1 crude lipid) diets containing an equal starch level (250 g kg^?1 starch) with different AM/AP ratio diets of 0/25, 3/22, 6/19, 9/16 and 12/13 were formulated. Each experimental diet was fed to triplicate groups (25 fish per tank), twice daily during a period of 60 days. After the growth trial, a postprandial blood response test was carried out. Fish fed diet 6/19 showed best growth, feed efficiency and protein efficiency ratio. Hepatosomatic index, plasma total cholesterol concentration, liver glycogen and lipid content, and gluconokinase, pyruvate kinase and fructose-1,6-bisphosphatase activities were lower in fish fed highest AM/AP diet (12/13) than in fish fed the low-amylose diets. Activities of liver and intestinal trypsin in fish fed diet 3/22 and diet 6/19 were higher than in fish fed diet 9/16 and diet 12/13. Activities of liver and intestinal amylase and intestinal lipase, and starch digestibility were negatively correlated with dietary AM/AP ratio. Fish fed diet 3/22 and diet 6/19 showed higher plasma total amino acid concentration than fish fed the other diets, while plasma urea nitrogen concentration and activities of alanine aminotransferase and aspartate aminotransferase showed the opposite trend. Equal values were found for viscerosomatic index and condition factor, whole body and muscle composition, plasma high-density and low-density lipoprotein cholesterol concentrations, and activities of lipase and hexokinase and glucose-6-phosphatase in liver. Postprandial plasma glucose and triglyceride peak value of fish fed diet 12/13 were lower than in fish fed the low-amylose diets, and the peak time of plasma glucose was later than in fish fed the other diets. Plasma glucose and triglyceride concentrations showed a significant difference at 2 and 4 h after a meal and varied between dietary treatments. According to regression analysis of weight gain against dietary AM/AP ratio, the optimum dietary AM/AP ratio for maximum growth of obscure puffer was 0.25. The present result indicates that dietary AM/AP ratio could affect growth performance and feed utilization, some plasma parameters, digestive enzyme as well as hepatic glucose metabolic enzyme activities in juvenile obscure puffer.     

Responses of cypermethrin-induced stress in haematological parameters of Korean rockfish, Sebastes schlegeli (Hilgendorf)

An increasing number of synthetic pyrethroids are used as an environmental friendly substitute of organophosphate and organochlorine insecticides. Pesticide pollution in the coastal ecosystem of Korea is considered to be a cause of slow growth and prevalence of diseases in commercial fishes. Therefore, it is necessary to develop fast techniques to detect insecticide toxicities. In the present work the results of rapid and inexpensive laboratory experiments show the patho‐physiological alteration of blood parameters to sublethal concentration of pyrethroid insecticide (cypermethrin) in the commercially important Korean rockfish (Sebastes schlegeli). Cypermethrin‐exposed fish showed erythropenia, low haematocrit and haemoglobin content and hyperglycemia, especially for long‐term exposure at high concentrations. Cypermethrin caused increased levels of serum glutamic‐acid‐oxylacetic‐acid‐transaminase, glutamic‐acid‐pyruvic‐acid‐transaminase and alkaline phosphatase, concomitant with a decreased concentration of chloride ion and blood serum osmolality, indicating the disruptive activity of cypermethrin after 8 weeks exposure. Moreover, reduced level of serum total protein, albumin, cholesterol, lysozyme activity and significantly higher level of glucose, bilirubin and malondialdehyde were measured and attributed to an increased demand for energy by fish under stress to cope with detrimental conditions imposed by chronic exposure to the toxicant.     

Physiological,ionoregulatory, metabolic and immune responses of Persian sturgeon,Acipenser persicus (Borodin, 1897) to stress

The physiological ionoregulatory, metabolic and immune responses of Persian sturgeon, Acipenser persicus, to acute stress were investigated. Water levels were lowered to the fish dorsal scutes, and fish were blood‐sampled before stress (pre‐stress), and 0, 6, 24 and 72 h after stress. Results showed that serum cortisol rapidly increased after stress, returning to initial levels at 24 h. Serum glucose significantly increased at 6 h, declining to the pre‐stress levels at 72 h. Serum triglyceride and cholesterol showed significant decreases at 0 h, then increasing to higher than the initial levels at 72 h. Serum T₃ and T₄ significantly decreased at 0 h and recovered at 72 h. Serum chloride levels showed no significant changes while serum calcium showed a significant increase at 0 h and a further increase until 72 h poststress. Serum total protein and alternative complement activity showed a significant initial decrease and recovery at 24 h with further increase at 72 h. Serum lysozyme activity increased significantly at 24 and 72 h after stress. Serum total immunoglobulin significantly increased at 0 h and peaked at 24 h. This is the first work showing thyroid hormone and immunological responses in Persian sturgeon subjected to stress, and the results show that this species follows a classical hormonal and energetic stress response, although, in the low range among the sturgeons. Although transient and moderate, confinement stress can induce significant changes in the innate immune response.     

Effects of stocking density on mortality,growth and physiology of juvenile Amur sturgeon (Acipenser schrenckii)

To evaluate effects of stocking density on welfare of Amur sturgeon (Acipenser schrenckii), an experiment was designed using three initial stocking densities in flow‐through tanks (LSD = 3.7 kg m^?3, MSD = 6.9 kg m^?3, and HSD = 9.3 kg m^?3, respectively) for 60 days. Growth, body composition, and haematological and biochemical parameters were monitored. The mortality and feed conversion rate (FCR) were not affected by stocking density. However, the specific growth rate (SGR), final weight and weight gain in the HSD group were significantly lower than in the LSD and MSD groups. The hepatosomatic (HSI) and viscerosomatic indices (VSI) varied inversely with regard to stocking density. Stocking density did not affect crude protein levels in fish. In contrast, the total lipid level was significantly higher in the LSD group compared to the MSD and HSD groups. The levels of erythrocytes and haemoglobin were positively correlated with stocking density. Serum total bilirubin and urea in HSD group were significantly higher than in the LSD group while serum triglycerides showed opposite tendencies. Differences between treatments were not registered for glucose, total protein and albumin. In conclusion, higher stocking density resulted in increased immunosuppression and enhanced energy mobilization. The latter was necessary to enable Amur sturgeon to cope with crowding.     

Effects of salinity level on the survival,growth, feed utilization,carcass composition,haematological and serum biochemical changes of juvenile Meagre (Argyrosomus regius) (Asso, 1801) grown in ground saltwater

A study was performed to examine the effects of salinity on water quality, fish performance, carcass composition and haemato‐biochemical parameters in juvenile meagre, Argyrosomus regius. Fish (5.0 g) were stocked in fibreglass tanks at four salinity levels: 8‰, 16‰, 24‰ and 32‰, and fed a pelleted diet (47/17 protein/lipid) for 56 days. Results indicated that the growth, feed utilization, carcass composition and haemato‐biochemical parameters of meagre gradually improved with the increase in salinity up to 24‰ and then significantly (p ≤ .05) decreased at 32‰. The survival per cent showed a significant decrease when A. regius exposed to 8‰ salinity. An improvement with 32%, 47% and 34.1% of FCR, protein productive value and energy utilization was detected at 24‰ compared with 8‰ salinity respectively. The highest content of protein and the lowest of lipids were recorded in fish carcass at 24‰ compared with the opposite trend at 8‰ salinity. The 24‰ salinity treatment exhibited the highest value of haemoglobin (4.9 g/dl) and the lowest ratio (0.73) of albumin/globulin. The serum total protein, albumin and globulin were significantly higher at 24‰ and 32‰ salinity than those at 8‰ and 16‰ salinity groups. These findings indicate that 24‰ salinity level might be the best for meagre.     

Minimally invasive evaluation of the anaesthetic efficacy of MS‐222 for ornamental discus fish using skin mucus biomarkers

Skin mucus has been demonstrated to provide stress biomarkers for evaluating the physiological status, providing new convenient and non‐invasive methods to detect stress response in fish. Here, we investigated the anaesthetic efficacy of tricaine methanesulphonate (MS‐222; 75–115 mg/L) for discus Symphysodon aequifasciata (34.27 ± 4.46 g; 8.10 ± 0.59 cm) using skin mucus stress biomarkers. The induction time, recovery time and respiratory frequency were also determined. According to the criteria for anaesthesia and recovery, discus fish to reach stage A3 (deep anaesthesia) within 3 min and to reach stage R4 (full recovery of normal behaviour) within 5 min were observed at 95–105 mg/L MS‐222. Respiratory frequency increased first and then decreased during MS‐222 exposure and increased after recovery. At 10 min after deep anaesthesia, a lower mucus glucose was only observed at 115 mg/L MS‐222. No change in mucus cortisol and increased lactate were observed in all treatments. Increased mucus protein was observed at 75, 85 and 95 mg/L MS‐222. At 10 min after recovery, increased mucus glucose and decreased mucus protein were observed at 85, 95 and 115 mg/L MS‐222, but increased mucus cortisol only at 115 mg/L and lactate only at 75 and 105 mg/L MS‐222. At 24 hr after recovery, mucus glucose returned to the initial level only at 75, 95 and 105 mg/L MS‐222, while cortisol at 75 and 85 mg/L and protein and lactate at 75 mg/L respectively. Overall, the effective dose of MS‐222 for discus fish has been suggested to be 95–105 mg/L.     

Effects of dietary yeast inclusion and acute stress on postprandial plasma free amino acid profiles of dorsal aorta‐cannulated rainbow trout

In a 4‐week experiment, 15 cannulated rainbow trout were fed three diets based on fish meal (FM), Saccharomyces cerevisiae yeast (SC) and Wickerhamomyces anomalus and S. cerevisiae yeast mix (WA). Fish were fed daily, and blood samples were collected on day 7 of each week at 0, 3, 6, 12 and 24 hr after feeding. In the final week, fish were exposed to a 1‐min netting stressor. All essential and non‐essential plasma amino acid levels except methionine were similar between fish fed diets FM, SC and WA. Plasma methionine and sarcosine were significantly higher in fish fed diets SC and WA, possibly due to the crystalline methionine level, form or feeding regime. Hydroxy‐proline and 3‐methyl‐histidine were higher in fish fed diet FM, which can be explained by the higher levels present in fish meal compared with yeast. In stressed fish, there were no dietary effects on plasma amino acid levels, but significant increases in taurine and cystathionine were found in stressed compared with unstressed fish. These results demonstrate that yeast‐based diets produce similar plasma amino acid profiles to fish meal and suggest that yeast may be a suitable fish meal replacement in diets for rainbow trout.     

Effects of ferulic acid on growth performance,immunity and antioxidant status in genetically improved farmed tilapia (Oreochromis niloticus) fed oxidized fish oil

A study was conducted to characterize the effects of dietary oxidized fish oil on the growth performance, immunity and antioxidant status of genetically improved farmed tilapia (Oreochromis niloticus) and to determine the role of ferulic acid on the oxidative damage induced by the oxidized fish oil. The tilapia (13.73 ± 0.31 g) were fed four experimental diets containing untreated (peroxide value, POV: 2.2 meq/kg) and highly oxidized (POV: 120.6 meq/kg) fish oil either with or without ferulic acid (0 or 400 mg/kg) supplementation for 12 weeks. From the results, the oxidized fish oil treatments increased antioxidant enzyme activities and MDA values but decreased the weight gain and the immunological parameters in tilapia. Meanwhile, the serum biochemical indices were significantly affected by the oxidized fish oil. Besides, the addition of ferulic acid partially counteracted the free radical‐induced damage and improved the health status of tilapia. In conclusion, the oxidized fish oil may induce oxidative stress, destroy liver, dysregulate lipid metabolism as well as reduce non‐specific immunity, and eventually result in growth inhibition of tilapia. The ferulic acid supplementation partially offset the negative effects of the oxidized fish oil on tilapia.     

Effect of dietary taurine supplementation on growth,digestive enzyme,immunity and resistant to dry stress of rice field eel (Monopterus albus) fed low fish meal diets

This study was conducted to evaluate the effect of dietary taurine supplementation on growth, immunity and resistant to dry stress of rice field eel (Monopterus albus) fed low fish meal diets. Six isonitrogenous and isolipid diets (32% fish meal) supplemented with six taurine concentrations (0, 0.3, 0.6, 0.9, 1.2 and 1.5 g/kg; designated as T₀, T_0.03, T_0.06, T_0.09, T_0.12 and T_0.15 groups, respectively) were prepared. A diet including 42% fish meal (FM group) was also included as a reference. The results showed that specific growth rate (SGR) in FM group was significantly higher than that in lower fish meal treatments. SGR significantly increased and slowly decreased with the increase in taurine supplementation level. Lipase activity value in intestine of M. albus fed FM diet was maximum, and with the increase in taurine supplementation level, lipase activity significantly increased and slowly decreased. The FM group had relative higher total antioxidant capacity (T‐AOC) content, catalase (CAT), total superoxide dismutase (T‐SOD), and lyzozyme (LZM) activities in serum than the other groups. With the increase in dietary taurine supplementation level, the CAT, T‐SOD, T‐AOC and LZM activities in serum significantly increased and then decreased. In the dry stress experience, the adrenaline (AD), cortisol (COR), glucose (GLU), total cholesterol (CHOL), and malondialdehyde (MDA) concentrations, T‐AOC content, CAT and T‐SOD activities in serum of M. albus in the four groups first increased and reached the peak at 2 hr, and then decreased under air‐exposure stress. Compared to the FM group, T_0.15 group had relative higher T‐AOC content, CAT and T‐SOD activities, and lower AD, COR GLU, TC and MDA concentrations.     

Effect of salinity on the rearing performance of juvenile golden pompano Trachinotus ovatus (Linnaeus 1758)

Effect of rearing salinity on the performance of juvenile golden pompano Trachinotus ovatus (Linnaeus 1758) was studied under a laboratory condition. Fish growth, survival, RNA/DNA ratio, pepsin activity, α‐amylase activity and FCR were used as evaluation criteria. The growth and RNA/DNA ratio were significantly affected by the rearing salinity. High growth rate and RNA/DNA ratio were observed when fish were reared at the salinity of 34‰. The pepsin activity of fish was not significantly affected by the rearing salinity. However, the α‐amylase activity of fish was significantly affected by the rearing salinity. The α‐amylase activity of fish reared at the salinity of 10‰ was significantly lower than fish cultured at the salinity of 34‰. Rearing salinity can significantly affect the FCR of juvenile golden pompano. The FCR of fish cultured at the salinity of 10‰ was 5‐times higher than the FCR of fish reared at 34‰. Results from the present study indicate that juvenile golden pompano can be reared above 26‰ without affecting fish performance, and the salinity of 10‰ may be too low to rear juvenile golden pompano as fish growth, RNA/DNA ratio and α‐amylase activity were reduced.