Hypoxia‐induced changes in survival,immune response and antioxidant status of the Pacific white shrimp (Litopenaeus vannamei) fed with graded levels of dietary myo‐inositol

A 3‐hr experiment was conducted to investigate the effects of dietary myo‐inositol (MI) supplementation on survival, immune response and antioxidant abilities in Litopenaeus vannamei under acute hypoxia stress. Six practical diets were formulated with supplementation of graded levels (control group 0, 0.1, 0.2, 0.4, 0.8 and 1.6 g/kg dry diet) of MI and were randomly assigned to triplicate groups of L. vannamei (mean weight 0.40 ± 0.00 g) for 8 weeks. Ten healthy shrimp (final mean weight approximately 11–14 g) randomly selected from each tank were exposed to hypoxia stress after feeding trial. After 3‐hr acute hypoxia stress, survival of shrimp fed MI‐supplemented diets (except 0.1 and 0.4 g/kg diets) was significantly increased compared with the control group. Shrimp fed control diet had lower activities of alkaline phosphatase (AKP), acid phosphatase (ACP), total antioxidant capacity (T‐AOC) and glutathione peroxidase (GPX), and higher malondialdehyde (MDA) and protein carbonyl (PC) contents in hepatopancreas than those fed the MI‐supplemented diets. In addition, mRNA expression levels of heat shock protein 70 (Hsp70), catalase (CAT) and penaeidin were significantly differentially regulated in hepatopancreas. In summary, dietary MI supplementation may have a positive effect on improving resistance to acute hypoxia stress of L. vannamei.     

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

The experiment was conducted to determine the leucine requirement of juvenile Pacific white shrimp Litopenaeus vannamei (Boone) in low‐salinity water (0.50–1.20 g L^?1). Six diets were formulated to contain 410 g kg^?1 crude protein with fish meal, peanut meal and precoated crystalline amino acids with different concentration of l ‐leucine (16.72, 19.60, 22.06, 24.79, 27.28 and 30.16 g kg^?1 dry diet). Each diet was randomly assigned to triplicate groups of 30 shrimps (0.38 ± 0.002 g), and the feed trial lasted for 8 weeks. The results indicated that the maximum weight gain was observed at 24.95 g kg^?1 dietary leucine group, whereas the diets containing higher leucine concentration conversely reduced the growth performance (P < 0.05). Moreover, the highest body protein content and body protein deposition and the lowest haemolymph AST and ALT activities were also found at 24.95 g kg^?1 dietary leucine group. With the increase in leucine in diets, a dose‐dependent increase was found in body lipid content and haemolymph urea concentration. The polynomial regression calculated using weight gain, feed efficiency and body protein deposition indicated that the optimal dietary leucine requirement for L. vannamei reared in low‐salinity water was 23.73 g kg^?1 leucine of dry diet, correspondingly 57.88 g kg^?1 of dietary protein.     

Effect of l‐ascorbyl‐2‐polyphosphate supplementation on growth performance,body composition,antioxidative capacity and salinity stress tolerance of juvenile Pacific white shrimp,Litopenaeus vannamei

An 8‐week feeding trial was conducted to evaluate the effects of ascorbic acid (AsA), in the form of l ‐ascorbyl‐2‐polyphosphate (LAPP) on growth performance, body composition, antioxidative capacity and salinity stress tolerance of juvenile Pacific white shrimp, Litopenaeus vannamei. Five practical diets (46% crude protein and 7.6% lipid) supplemented with graded levels of AsA (14.64, 48.55, 84.98, 308.36 and 639.27 mg kg^?1 diet) were fed to five replicate groups of L. vannamei (mean initial wet weight 0.57 g). No significant differences were found on growth performance among all treatments. However, whole body lipid content significantly decreased with dietary AsA levels increasing. Activities of total antioxidant capacity, glutathione reductase and glutathione peroxidase were significantly affected by dietary AsA levels. Shrimp fed LAPP‐free diet had higher malondialdehyde content than those fed the diets supplemented with LAPP. Dietary AsA levels higher than 308.36 mg kg^?1 diet increased the survival of shrimps after 1, 2 and 3 h of acute salinity change. Broken‐line regression analysis on survival after 3 h of salinity stress and second‐degree polynomial regression analysis on glutathione reductase data indicated that the optimal dietary AsA requirement of L. vannamei was estimated to be 306.39, 319.75 mg kg^?1 diet respectively.     

Effect of γ‐aminobutyric acid supplementation on growth performance,endocrine hormone and stress tolerance of juvenile Pacific white shrimp,Litopenaeus vannamei,fed low fishmeal diet

An 8‐week feeding trial was conducted to evaluate the optimum dietary γ‐aminobutyric acid (GABA) level in low fishmeal diet for juvenile Pacific white shrimp, Litopenaeus vannamei. Six practical diets (449 g kg^?1 protein, 87 g kg^?1 lipid) supplemented with graded levels of GABA (0, 50, 100, 150, 200, 250 mg kg^?1) were formulated. Each diet was randomly assigned to triplicate groups of 30 shrimps (approximately 0.44 g), and the shrimps were fed four times a day to apparent satiation. Weight gain and gain rate were significantly increased with the supplementation of GABA (P < 0.05). Hepatosomatic index and survival were also significantly influenced by the dietary GABA levels (P < 0.05) and show a similar trend to those of growth performance. Insulin and neuropeptide Y concentrations in blood were increased with the supplementation of GABA. In total, 150 mg GABA kg^?1‐supplemented diets significantly increased the survival after 12, 24 and 36 h of NH₃ stress, also increased the total antioxidant capacity, total superoxide dismutase, catalase, antihydroxyl radical and phenoloxidase activities before and after the 36 h NH₃ stress compared to basic group. These results clearly indicated that GABA could improve growth performance, antioxidative capacity and resistance against NH₃ stress in L. vannamei, and 150 mg kg^?1 GABA supplementation was suitable for L. vannamei fed with low fishmeal diet.     

Dietary thiamin could improve growth performance,feed utilization and non‐specific immune response for juvenile Pacific white shrimp (Litopenaeus vannamei)

This study evaluated the effect of dietary thiamin on growth performance, feed utilization and non‐specific immune response for juvenile Pacific white shrimp, Litopenaeus vannamei. Six isonitrogenous and isolipidic practical diets were formulated with graded thiamin levels of 6.9, 32.7, 54.2, 78.1, 145.1 and 301.5 mg kg^?1 of dry diet, respectively. Each diet was randomly assigned to triplicate groups of 30 juvenile shrimp and provided four times each day to apparent satiation. Weight gain (WG) and specific growth rate (SGR) of the shrimp were significantly influenced by the dietary thiamin levels, the maximal WG and SGR occurred at 54.2 mg kg^?1 dietary thiamin level. However, with further increase in dietary thiamin level from 54.2 to 301.5 mg kg^?1, the WG and SGR significantly decreased. Shrimp fed the 54.2 mg kg^?1 thiamin diet exhibited higher feed efficiency, protein efficiency ratio and protein productive value than those fed the other diets. Dry matter and protein content in whole body were significantly affected by the dietary thiamin levels. Thiamin concentration in hepatopancreas significantly increased when the dietary thiamin level increased from 6.9 to 145.1 mg kg^?1. The total protein, glucose, triacylglycerol and cholesterol contents in hemolymph were not significantly affected by the dietary thiamin levels. Dietary thiamin had significantly influenced superoxide dismutase, catalase and lysozyme activities in hemolymph. Results of this study indicated that the optimal dietary thiamin requirements estimated using a two‐slope broken‐line model based on WG and thiamin concentration in hepatopancreas were 44.66 and 152.83 mg kg^?1, respectively.     

Growth,body composition,ammonia tolerance and hepatopancreas histology of white shrimp Litopenaeus vannamei fed diets containing different carbohydrate sources at low salinity

Juvenile Litopenaeus vannamei farmed at 3.0 psu were fed five diets containing glucose, sucrose, wheat starch, corn starch or potato starch as the carbohydrate (CBH) source. Shrimp were fed for 50 days to explore the effect of dietary CBH source on growth, body composition and ammonia tolerance. The specific growth rate of body length of shrimp fed glucose was the highest and significantly higher than those fed potato starch. The survival rate of shrimp fed glucose was 89.44%, and it was the highest and significantly higher than those fed wheat starch. Whole shrimp body crude protein and lipid of the corn starch group were 140.2 g kg^?1 and 10.1 g kg^?1 respectively. And they were significantly higher than those fed wheat starch. Shrimp fed potato starch had higher hepatopancreas and muscle glycogen. Shrimp fed sucrose had higher glucose‐6‐phosphate dehydrogenase and lower pyruvate kinase activities (P < 0.05). Besides, shrimp fed starch produced more B cells in hepatopancreas tubules than those fed glucose or sucrose. Shrimp fed different sources of CBH differed in the number of R cells. After 96‐h of ammonia nitrogen challenge, the survival rate of the treatments from high to low in turn was glucose, wheat starch, corn starch, sucrose and potato starch, and no significant differences were observed among all treatments. Based on shrimp growth and the economic problems of practical production, we recommend wheat starch as CBH source in practical diets for L. vannamei farmed at low salinities.     

Effect of dietary vitamin B6 on growth,feed utilization,health and non‐specific immune of juvenile Pacific white shrimp,Litopenaeus vannamei

Six diets were formulated with vitamin B₆ levels (2.6, 32.7, 54.8, 90.7, 119.6 and 247.4 mg kg⁻¹, dry diet) to determine the requirement for juvenile Pacific white shrimp, Litopenaeus vannamei. Triplicate groups of 40 juvenile shrimp (approximately 1.0 g) were provided four times each day to apparent satiation (8 weeks). Weight gain (WG), specific growth rate, feeding efficiency, protein efficiency ratio (PER) and protein productive value of the shrimp were significantly influenced by the vitamin B₆ levels. No significant differences in whole‐body and muscle composition, except for dry matter and protein contents in whole body. Vitamin B₆ concentration in the hepatopancreas significantly increased with the dietary vitamin B₆ level increasing from 2.6 to 32.7 mg kg⁻¹. High‐density lipoprotein cholesterol in the haemolymph improved with the dietary vitamin B₆ levels increasing from 2.6 to 90.7 mg kg⁻¹ diet and no significant differences in low‐density lipoprotein cholesterol, cholesterol, glucose and total protein concentrations. Aspartate aminotransferase, alanine aminotransferase, superoxide dismutase, catalase and lysozyme in the haemolymph were significantly influenced by dietary vitamin B₆ levels. The optimal dietary vitamin B₆ requirements estimated using a two‐slope broken‐line model based on WG and SGR and an exponential model based on the vitamin B₆ concentration in the hepatopancreas were 110.39, 110.08 and 167.5 mg kg⁻¹, respectively.     

Dietary myo‐inositol requirement for juvenile gibel carp (Carassius auratus gibelio)

An 11‐week growth trial was conducted to determine dietary myo‐inositol (MI) requirement for juvenile gibel carp (Carassius auratus gibelio). Myo‐inositol was supplemented to the basal diet to formulate six purified diets containing 1, 56, 107, 146, 194 and 247 mg MI kg^?1 diet, respectively. Each diet was fed to triplicate groups of juvenile gibel carp (initial body weight 3.38 ± 0.27 g, mean ± SD) in a flow‐through system. The diets were randomly assigned to different fish tanks. Fish fed ≥ 107 mg MI kg^?1 diet had significantly higher weight gain (WG), feed efficiency (FE) and protein efficiency ratio than those fed 1 mg MI kg^?1 diet. Fish fed ≥ 56 mg MI kg^?1 diet had higher feeding rate and survival compared with fish fed 1 mg MI kg^?1 diet. Dietary supplemental inositol did not affect fish liver inositol concentration. Fish fed ≥ 56 mg MI kg^?1 diet had higher body dry matter, crude protein and gross energy and lower hepatosomatic index than fish fed 1 mg MI kg^?1 diet. Dietary inositol supplementation decreased fish body ash. Quadratic regression of weight gain indicated that the myo‐inositol requirement to maximum growth for juvenile gibel carp was 165.3 mg MI kg^?1 diet.     

Genetic parameters for spawning and growth traits in the Pacific white shrimp (Penaeus (Litopenaeus) vannamei)

The aim of this study was to estimate genetic parameters for spawning traits and growth traits in a breeding line of Pacific white shrimp, Penaeus (Litopenaeus) vannamei, selected for growth and survival. Traits studied were number of eggs (NE) and number of nauplii (NN) and female body weight at insemination (FWI) and body weight at 130 days of age (BW130). Genetic parameters were estimated using a multivariate animal model. Heritability for NE and NN were estimated as 0.13 ± 0.04 and 0.03 ± 0.04 respectively. The contribution to NN total variation due to ‘factors associated with male’ effect was estimated as 0.47 ± 0.07. In the cases of FWI and BW130, heritability was estimated as 0.44 ± 0.08 and 0.19 ± 0.03 respectively. Genetic correlation between FWI and NE was estimated as 0.49 ± 0.15, between FWI and NN as 0.54 ± 0.39 and between NE and NN as 0.27 ± 0.41, whereas the genetic correlations of FWI, NE and NN with BW130 were 0.30 ± 0.13, ?0.21 ± 0.19 and ?0.25 ± 0.38 respectively. Although it is important to perform more studies on this issue, our results found no evidence of a genetic antagonistic effect between female reproductive traits and body weight at harvesting (130 days of age) in P. vannamei.     

Effects of dietary astaxanthin on growth,antioxidant capacity and gene expression in Pacific white shrimp Litopenaeus vannamei

Pacific white shrimp Litopenaeus vannamei (1050 individuals with initial weight of 1.01 ± 0.001 g) were fed either control diet or one of six dietary astaxanthin (AX) concentration (25, 50, 75, 100, 125 and 150 mg kg⁻¹) diets for 56 days in 35 tanks (30 shrimp per tank). After 56 days of culture, shrimp‐fed AX125 and AX150 diets had higher (P < 0.05) weight gain, specific growth rate, total antioxidant status and lower (P < 0.05) superoxide dismutase (SOD), catalase (CAT) than shrimp fed control diet. After low dissolved oxygen stress for 1 h, survival rate of shrimp fed AX75, AX100, AX125 and AX150 diets was higher (P < 0.05) than that of shrimp fed control diet. Hypoxia inducible factor‐1α (HIF‐1α), cytosolic manganese superoxide dismutase (cMnSOD) and CAT mRNA expression levels of shrimp fed seven diets were significantly down‐regulated under hypoxia than under normoxia, but their expression levels were higher under hypoxia in shrimp fed AX‐supplemented diets than in shrimp fed control diet. About 70‐kDa heat‐shock protein (Hsp70) mRNA expression level of shrimp fed seven diets was significantly up‐regulated under hypoxia than under normoxia, but its expression level was lower under hypoxia in shrimp fed AX‐supplemented diets than in shrimp fed control diet.     

Effects of dietary n‐3HUFA on juvenile white shrimp,Litopenaeus vannamei: Growth,feed utilization,antioxidant enzymes activities and fatty acid compositions

Present study investigates the effects of n‐3 high‐unsaturated fatty acid (n‐3HUFA) levels on growth performance, antioxidant enzymes activities and fatty acid compositions of juvenile Litopenaeus vannamei. These represented seven iso‐nitrogenous and iso‐lipidic diets. Analysed n‐3HUFA concentrations were 0.16% (control), 0.48%, 0.74%, 1.39%, 2.39%, 2.92% and 3.44% respectively. A total of 840 juvenile L. vannamei were randomly stocked into 21 0.5 m³ tanks for 56 days. A significant increase (p < 0.05) was observed from 0.16% to 0.74% n‐3HUFA and a decrease when n‐3HUFA was above these levels in weight gain rate (WGR) and specific growth rate. Total cholesterol, triglyceride and low‐density lipoprotein in serum showed a significant decrease, high‐density lipoprotein showed a significant increase (p < 0.05). Phenoloxidase activity in serum and sodium‐potassium adenosine triphosphatase activity in gill were significantly affected by dietary n‐3HUFA (p < 0.05), both of them showing a downward trend after upward. Malic dehydrogenase and superoxide dismutase activities in serum were also significantly affected by dietary n‐3HUFA (p < 0.05), which rose first and then decreased in general, both of them have a maximum in 2.39% group. No significant differences of the activities of aspartate transaminase and alanine transaminase were observed among all groups (p > 0.05). With dietary n‐3HUFA increase, both ∑HUFA and n‐3HUFA contents gradually increased in hepatopancreas and tail muscles (p < 0.05). Based on broken‐line regression analysis of WGR, the optimal n‐3HUFA requirement is 0.89% for juvenile L. vannamei with initial weight of 0.50 ± 0.01 g.     

Effects of dietary supplementation of Astragalus membranaceus,Codonopsis pilosula,and Glycyrrhiza uralensis extract mixture on growth performance,haematological parameters and hepatopancreatic performance in juvenile Pacific white shrimp (Litopenaeus vannamei)

Pacific white shrimp is the major farmed shrimp species in the world. It is known to be very sensitive to the environmental and management changes such as intensification, which is one of the primary necessities to increase shrimp production, but represents a stressful condition, and needs to be managed properly to diminish its negative effects in aquaculture. In this study, juvenile Pacific white shrimp were fed diets supplementing with equal quantities of Astragalus membranaceus, Codonopsis pilosula and Glycyrrhiza uralensis extracts in different concentrations (0, 1.0, 2.0 and 3.0 g/kg) for 8 weeks. We subsequently estimated the effects of supplemented diets on growth performance, haematological parameters, and histological changes of hepatopancreas. Results revealed that the supplemented mixture had no benefits on growth and survival rate, but had favourable effects on haemocyte count, number of granulocytes, and hemocyanin concentration in the haemolymph (p > 0.05). We observed that R cells and B cells were increased in hepatopancreatic tubules of shrimps fed on supplemented diets. Besides, a diet containing 2.0 g/kg of extract mixture maintained the decreased levels of alanine aminotransferase (p < 0.05) and aspartate aminotransferase (p > 0.05). Among the used concentrations, 2.0 g/kg seemed to be the most suitable concentration.     

Effects of dietary dl‐methionyl‐dl‐methionine (Met‐Met) on growth performance,body composition and haematological parameters of white shrimp (Litopenaeus vannamei) fed with plant protein–based diets

A 10‐week feeding trial was conducted to evaluate the effects of supplementing different levels of dl ‐methionyl‐dl ‐methionine (AQUAVI^® Met‐Met) in plant protein–based diets on Litopenaeus vannamei. The positive control (PC) and negative control (NC) diets were designed with 20% and 8% fishmeal respectively, and other six diets were formulated with graded levels of Met‐Met from 0.05% to 0.30% with a 0.05% increment on the basis of NC diet (MM 0.05–MM 0.3). Six replicates were randomly assigned to each diet with 50 shrimp each having initial weight of 0.98 ± 0.02 g. The variation of FM concentration from 20% to 8% and supplemented with graded levels of Met‐Met did not affect the survival rate, feed conversion ratio, protein efficiency ratio, whole body and muscle proximate compositions (p > 0.05). However, diets with ≤0.20% Met‐Met supplementation resulted in significantly increased weight gain and specific growth rate, after which both parameters reached plateau. Shrimp fed the NC diet showed significantly lower total essential amino acid (EAA) content in muscle (p < 0.05). Supplementation of Met‐Met significantly improved apparent digestibility coefficients of dry matter, crude protein, lipid, phosphorus and EAAs (p < 0.05). Based on broken‐line analysis, the methionine requirement for white shrimp was estimated to be 0.87% when using Met‐Met as methionine source.     

Effects of dietary n‐3HUFA on different growth stages of the white shrimp,Litopenaeus vannamei: Growth,haematological characteristics,enzyme activities and fatty acid profiles

This study investigated the effects of n‐3 high unsaturated fatty acid (n‐3HUFA) levels on the growth performance, antioxidant enzyme activities and fatty acid profiles of both subadult and adult Litopenaeus vannamei (L. vannamei). Seven iso‐nitrogenous and iso‐lipidic diets were used, containing n‐3HUFA concentrations of 1.6 (control), 4.8, 7.4, 13.9, 23.9, 29.2 and 34.4 g/kg, respectively. Two 8‐week feeding trials were conducted to determine the dietary n‐3HUFA requirements of L. vannamei with an initial body weight of 4.25 ± 0.00 g (subadults) and 8.50 ± 0.01 g (adults). The results showed that the dietary n‐3HUFA level significantly affected the weight gain rate (WGR), specific growth rate, the feed conversion ratio and the hepatosomatic index (HSI) (p < 0.05), but did not significantly affect the survival rate (p > 0.05). At appropriate level, dietary n‐3HUFA improved growth performance and HSI of both subadult and adult L. vannamei. Both subadults and adults showed significant differences in body composition (p < 0.05), except for moisture and crude ash (p > 0.05). Cholesterol and low‐density lipoprotein significantly decreased with increasing dietary n‐3HUFA both in subadults and adults (p < 0.05); however, triglyceride showed no significant change (p > 0.05). High‐density lipoprotein (HDL) in subadults was significantly affected by dietary n‐3HUFA (p < 0.05), but followed no apparent regularity; HDL significantly changed in adults and showed an upward trend followed by a downward trend (p < 0.05). There was no significant effect on aspartate transaminase (AST) activity in subadults, but AST in adults and alanine transaminase (ALT) in subadults and adults were significantly affected (p < 0.05). Dietary n‐3HUFA significantly affected serum polyphend oxidase, malic dehydrogenase, alkaline phosphatase, superoxide dismutase and sodium‐potassium adenosine triphosphatase enzyme activities in gills (p < 0.05). The fatty acid composition of the shrimp tissue was associated with the fatty acid composition of the diet. Dietary n‐3HUFA supplementation significantly improved the contents of tissue ∑HUFA and n‐3HUFA, increased the n‐3/n‐6 ratio in the tail muscle and decreased the contents of tissue polyunsaturated fatty acid and saturated fatty acid (p < 0.05). Based on the WGR, the broken‐line equations indicated that the optimum requirements of dietary n‐3HUFA were determined to be 9.0 and 5.1 g/kg for subadult and adult L. vannamei, respectively.     

Effects of dietary aflatoxin B1 on growth performance,body composition,haematological parameters and histopathology of juvenile Pacific white shrimp (Litopenaeus vannamei)

An 8‐week feeding trial was conducted to evaluate the effects of dietary aflatoxin B₁ (AFB₁) on growth performance, haematological parameters and histological changes in juvenile Pacific white shrimp, Litopenaeus vannamei. Six practical diets (455 g kg^‐1 protein, 78 g kg^‐1 lipid) with different levels of AFB₁ (0, 25, 50, 100, 500, 1000 μg kg^?1) were formulated. Each diet was fed to triplicate groups of shrimps (initial weight: 0.52 g). The results showed that shrimp fed with control diet (0 μg kg^?1 AFB₁) had significant higher weight gain (WG) and specific growth rate (SGR) than other groups. However, there were no significant differences in feed efficiency (FE) or hepatosomatic index (HSI) among all groups. Compared to the control diet, AFB₁ supplementation significantly changed the activities of shrimp serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total antioxidant capacity (T‐AOC) and glutathione S‐transferase (GST) and the content of cholesterol (CHO). Histological damages were identified in the hepatopancreas of shrimp when dietary AFB₁ level was over 107.6 μg kg^?1. Based on this study, it was concluded that the AFB₁ level in Pacific white shrimp diet should be <38.1 μg kg^?1.     

Effects of various dietary levels of copper hydroxychloride on growth performance and tissue response in Pacific white shrimp Litopenaeus vannamei fed practical diets

Two trials were conducted to evaluate the performance of Pacific white shrimp Litopenaeus vannamei offered diets containing various copper (Cu) levels from Cu hydroxychloride (Cu₂(OH)₃Cl) containing 58.81% copper in the clear water recirculating system. In both trials, the basal diet (360 g kg^?1 protein, 80 g kg^?1 lipid) containing approximately 10 mg Cu kg^?1 was primarily comprised of fishmeal, soybean meal, corn protein concentrate and whole wheat. In trial 1, test diets were produced supplementing the basal diet with 5, 10, 20, 40 and 60 mg Cu kg^?1 from Cu hydroxychloride. Four replicate groups of 15 shrimp per tank (initial weight 0.28 g) were offered diets in slight excess over 8 weeks. In trial 2, the basal diet was supplemented with 30, 90, 150, 210 and 270 mg Cu kg^?1 from Cu hydroxychloride. Seven replicate groups of 15 shrimp per tank (initial weight 0.22 g) were offered feed in slight excess over 7 weeks. At the end of the two growth trials, no significant differences were observed in final biomass, final mean weight, percentage weight gain, feed conversion ratio (FCR) and survival. In trial 1, the Cu concentrations of the carapace, hepatopancreas and whole shrimp linearly increased with increasing dietary Cu supplements. In trial 2, polynomial regression of Cu concentrations of the carapace, hepatopancreas and whole shrimp against analysed dietary Cu content indicated that a plateau was reached at 215 mg analysed Cu kg^?1. Results of this study indicate that there was no negative effect of high levels of Cu supplement with regard to growth and survival. Tissue levels generally increased up to around 200 mg Cu kg^?1 diet and then decreased, possibly indicating a shift in physiology.     

Effect of dietary lipid level on growth,lipid metabolism and health status of the Pacific white shrimp Litopenaeus vannamei at two salinities

Three isonitrogenous diets containing 60 g kg^–1, 90 g kg^–1 or 120 g kg^–1 lipid were formulated and fed to the Litopenaeus vannamei (2.00 ± 0.08 g) under two salinities (25 or 3 psu) in triplicate for 8 weeks. Shrimp fed 90 g kg^–1 lipid had higher weight gain and specific growth rate than shrimp fed the other two diets regardless of salinity, and the hepatosomatic index increased with increasing dietary lipid at both salinities. The shrimp at 3 psu had significantly lower survival and ash content, higher condition factor, weight gain and specific growth rate than the shrimp at 25 psu. Increasing dietary lipid level induced the accumulation of serum MDA regardless of salinity, and at 3 psu, it reduced the serum GOT and GPT activities and the mRNA expression of TNF‐α in intestine and gill of L. vannamei. The hepatopancreatic triacylglycerol lipase (TGL) and CPT‐1 mRNA expression showed the highest value in shrimp fed 90 g kg^–1 lipid diet at 3 psu. This study indicates that 120 g kg^–1 dietary lipid may negatively affect the growth and induce oxidative damage in shrimp, but can improve immune defence at low salinity; 60 g kg^–1 dietary lipid cannot afford the growth and either has no positive impact on the immunology for L. vannamei at 3 psu.