Growth,parasitic infection and hematology in Colossoma macropomum Cuvier, 1818 fed diets containing Allium sativum

The aim of this study was to investigate the effects of a dietary Allium sativum (garlic) addition on growth, parasite infestation and blood parameters in Colossoma macropomum (tambaqui) using 12 net‐cages (1 m³). There were four treatments with three replicates each (15 fish per replicate). Tambaqui of 112.4 g mean weight were fed for 45 days with diets containing 0, 15, 30 and 45 g of fresh garlic kg^?1 feed. Garlic did not affect the tambaqui survival, growth, feed conversion, body condition, plasma glucose levels, total plasma protein levels or red blood cells. Total leukocyte and lymphocyte numbers decreased in fish fed diets containing 45 g garlic kg^?1 feed, but neutrophils decreased in fish fed diets containing 15, 30 and 45 g garlic kg^?1 diet, while the number of immature leukocytes increased in fish fed 30 g and 45 g garlic kg^?1diet. Gills in fish fed 30 and 45 g kg^?1 diet had lower infestation (52% and 63%, respectively) of Anacanthorus spathulatus (Monogenea) compared to controls. The application of garlic in diets improved the response of leukocytes and enhanced the resistance to infections by monogeneans.     

Effects of β‐xylanase and 6‐phytase on digestibility,trace mineral utilisation and growth in juvenile red tilapia,Oreochromis niloticus (Linnaeus, 1758) x O. mossambicus (Peters, 1852), fed declining fishmeal diets

In response to the global sustainability drive to lower fishmeal (FM) inclusion in aquatic feeds, exogenous enzymes can improve nutrient digestibility in monogastric plant‐based diets. A 80‐day experiment was conducted to evaluate the combined effects of xylanase and phytase on digestibility, trace mineral utilisation and growth in juvenile red tilapia, Oreochromis niloticus x O. mossambicus, (48.8 g ± 13.9; μ ± STD) fed declining FM diets. Basal diets were formulated to contain 0, 3 and 5% FM with and without xylanase (0.385 g kg^?1) and phytase (0.075 g kg^?1), forming six treatments. Each treatment was randomly assigned to four replicates, 20 fish tank^?1; mean water temperature 28.98 ± 0.73°C. Although the size of the effects was modest, growth performances (feed intake, FCR, growth rate) decreased with lower FM levels (P < 0.05) but improved with enzyme supplementation. Enzyme supplementation increased P digestibility and trace mineral uptake (P < 0.05), but no effects were seen on protein digestibility and N retention. Nevertheless, tilapia fed the enzyme‐supplemented 3% FM and control 5% FM diets performed comparably (P < 0.05). This potentially justifies a 2% FM reduction for tilapia diets using exogenous xylanase and phytase without significant effects on digestibility, trace mineral utilisation and growth.     

Effect of dietary dextrin levels on the growth performance,blood chemistry,body composition,hepatic triglicerides and glycogen of Lebranche mullet juveniles (Mugil liza Valenciennes 1836, Mugilidae)

The effects of increasing levels of dietary dextrin on growth performance, body composition, blood chemistry and hepatic triglycerides and glycogen levels were evaluated for juvenile Lebranche mullet, Mugil liza Valenciennes 1836, Mugilidae). Five diets were formulated to be isonitrogenous (350 g kg^?1) and isolipidic (6 g kg^?1) with increasing dextrin levels (D150: 150 g kg^?1; D200: 200 g kg^?1; D250: 250 g kg^?1; D300: 300 g kg^?1; D350: 350 g kg^?1). The experimental diets were offered to the fish for 34 days, four times per day, until apparent satiation. Each treatment was tested in triplicate, with nine fish per tank (mean weight 4.69 ± 0.31 g). Fish were reared in a recirculating aquatic system of 15 fibreglass tanks each containing 50 L of saltwater. Growth parameters and body composition of the mullets were not significantly affected (P > 0.05) by the dietary treatments. Plasma glucose concentration declined (P < 0.05) when dietary dextrin increased from D250 to D300, but recovered to the previous values (in reference to D150 and D200) when fish were fed with D350. Glycated haemoglobin, plasma proteins, triglycerides and cholesterol showed no significant differences among these treatments. Hepatic glycogen reached a maximum in treatment D250, followed by D350, D200 and D300, with the lowest concentration of liver glycogen found in D150 (P < 0.05). The concentration of liver triglycerides showed an increase (P < 0.05) in treatments D300 and D350 compared with D200. In conclusion, Mugil liza juveniles can be fed diets with high levels of dietary dextrin with no deleterious effects to their growth or plasma biochemistry, hepatic glycogen or triglycerides.     

Immunomodulatory effect of sodium alginate enriched diet in kelp grouper Epinephelus brneus against Streptococcus iniae

The effect of diets containing sodium alginate at 0, 0.5, 1.0, and 2.0 g kg^?1 following challenge with Streptococcus iniae in kelp grouper Epinephelus bruneus were assessed with reference to survival rate and innate immune parameters such as alternative complement, lysozyme, natural haemagglutination, respiratory burst, superoxide dismutase, and phagocytic activities on week 1, 2, and 4. Fish fed with sodium alginate containing diet at 1.0 and 2.0 g kg^?1 after being challenged with S. iniae had higher survival rates of 75% and 60%, respectively than those fed with control diet (0 g kg^?1). With any enriched diet the percentage of macrophages significantly decreased from week 1–4, while the percentage of neutrophils and lymphocytes significantly increased. The alternate complement activity, natural haemagglutination, and phagocytic activities of infected fish fed with sodium alginate containing diet at 1.0 g kg^?1 on week 2 and 1.0 and 2.0 g kg^?1 diets on week 4 were significantly higher when compared to the control. The lysozyme, respiratory bursts, and superoxide dismutase activities of fish fed with enriched diets at 1.0 and 2.0 g kg^?1 were significantly increased on week 2 and 4. We therefore recommend that at 1.0 or 2.0 g kg^?1 dietary administration of sodium alginate can enhance innate immunity and disease resistance in kelp grouper against S. iniae.     

Effects of varying levels of dietary vitamin E (α‐tocopherol) on growth performance,proximate and fatty acid composition of juvenile silver pomfret (Pampus argenteus Euphrasen, 1788)

This study investigated the effects of elevated dietary levels of vitamin E (α‐tocopherol) on growth performance, proximate composition and fatty acid profiles of juvenile silver pomfret, Pampus argenteus. Three semi‐purified experimental diets were formulated to contain 49% protein and 16% lipid. High docosahexaenoic acid (DHA) tuna oil was added to the diets to supplement DHA. A graded level of vitamin E (0‐, 50‐, and 100 mg kg^?1) was added to experimental diets 1 to 3, respectively. Analyzed vit. E levels were 155.2, 195.3 and 236.4 mg kg^?1 in diets 1, 2 and 3, respectively. The experiment was conducted for 12 weeks with juvenile silver pomfret (29.6 ± 7.6 g) using a flow‐through system consisting of nine 1‐m³ tanks. Each treatment had three replicates and fish were stocked at the rate of 20 m^?3. Growth performance and feed utilization parameters of fish fed diets 2 and 3 were significantly (P < 0.05) higher than in fish fed diet 1, but the parameters in diets 2 and 3 did not differ significantly (P > 0.05). Although whole body protein levels were not influenced by the dietary vit. E levels, whole body lipid in fish fed diet 2 was significantly higher than in fish fed the other diets. The whole body vit. E levels in fish fed diet 2 (22.6 mg kg^?1) and diet 3 (24.1 mg kg^?1) were significantly (P < 0.05) higher than in those fed diet 1 (18.2 mg kg^?1). Whole body total saturated fatty acids were significantly lower, and DHA levels higher in fish fed diets 2 and 3 than those fed diet 1. The results of the present study suggest that increasing dietary supplementation of vit. E in high lipid diets enhances the growth performance of fish and that a dietary level of 196 mg kg^?1 vit. E is suitable for the growth of silver pomfret.     

Effect of high‐dose vitamin C supplementation on growth,tissue ascorbic acid concentrations and physiological response to transportation stress in juvenile silver pomfret,Pampus argenteus

This study investigated the effect of high‐dose vitamin C supplementation on growth, tissue ascorbic acid concentrations and physiological response to transportation stress in juvenile silver pomfret, Pampus argenteus (initial average weight 6.2 ± 0.2 g). Three practical diets were formulated to contain 100 (control), 450 and 800 mg ascorbic acid/kg diet, respectively, supplied as l‐ascorbyl‐2‐polyphosphate. Each diet was fed to triplicate groups of fish in circular tanks (3 m ø, 1.5 m depth) (60 fish/tank) for 9 weeks. Growth did not change significantly with dietary vitamin C levels, although an improvement tendency with an increase in vitamin C supplementation was observed. Ascorbic acid concentrations in the liver and muscle of fish fed diets containing graded levels of vitamin C were positively correlated with dietary levels of this vitamin. Tissue ascorbic acid concentrations significantly increased with increasing vitamin C supplementation. After 9 weeks, the fish were subjected to transportation stress for 4 h to determine the influence of high vitamin C supplementation on the physiological response to this stressor. Serum cortisol, glucose and lactate levels significantly increased in stressed fish. Serum cortisol and glucose concentrations after stress were significantly higher in fish fed the control diet (7.91 μg L^?1 and 0.80 mm , respectively) than in the other groups. However, there were no significant differences in serum cortisol and glucose levels after stress between the 450 and 800 mg kg^?1 diets. No significant change could be found in serum lactate levels after stress among the different treatments. In conclusion, the dietary administration of high doses of vitamin C could reduce stress in silver pomfret and increase the survival of fish under stress conditions.     

Partial replacement of monocalcium phosphate with neutral phytase in diets for grass carp,Ctenopharyngodon idellus

A 9‐week experiment was designed to study the effects of partial replacement of monocalcium phosphate (MCP) with neutral phytase on growth, body compositions, serum biochemical statuses and intestinal digestive enzyme activities of grass carp, Ctenopharyngodon idellus. The control diet (designated as P2.0) was prepared with 2.0% MCP but without phytase. The three other diets (designated as PP1.5, PP1.0 and PP0.5, respectively) were supplemented with 1.5, 1.0 and 0.5% MCP, respectively, along with 500 FTU of neutral phytase kg^?1 diet in each. After a 9‐week feeding trial, fish (initial body weight: 43.44 ± 2.37 g) fed with PP1.5 and PP1.0 had no significant change in weight gain (WG), specific growth rate (SGR), protein efficiency rate (PER) or feed conversion ratio (FCR) compared with the control (P > 0.05) whereas fish fed with PP0.5 showed significantly lower growth performance in the above parameters. The crude lipid content in whole body or muscle of the fish fed with PP1.5 was significantly lower than the control while significantly higher in fish fed with PP0.5 (P < 0.05), whereas no obvious change was observed in the fish fed with PP1.0. For serum indices, higher serum alkaline phosphatase (Alkp), phosphorus (P) and calcium (Ca) contents were observed in fish fed with phytase‐supplemented diets in comparison with the control. In addition, dietary phytase supplementation increased amylase activity and decreased lipase activity in both foregut and hindgut. The present study suggests that dietary MCP can be reduced when neutral phytase is added to the grass carp diet, and that the maximum MCP reduction level can be up to 1% when neutral phytase is supplemented at 500 FTU kg^?1 diet.     

Evaluation of optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel,Anguilla japonica

The study aimed at evaluating the optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel, Anguilla japonica, as assessed by fish growth performance and fish body composition. Five semi‐purified experimental diets were formulated to contain 0 (TA₁), 15 (TA₁₇), 30 (TA₃₂), 60 (TA₆₂) and 120 (TA₁₁₉ mg TA kg^?1 diet on a dry matter (DM) basis in the form of DL‐α‐tocopheryl acetate (TA). After a 4‐week conditioning period, fish (15 ± 0.3 g) were randomly distributed into aquaria in groups of 20 at 25 ± 1.0°C (mean ± SD). One of the five diets was fed on a DM basis to fish in three randomly selected aquaria twice daily to satiation (approximately 3% of wet body weight per day at the beginning and 2% of wet body weight per day at the end of the feeding trial) for 12 weeks. At the end of the 12‐week feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) were determined; these were significantly lower in control fish than in fish fed supplemented diets (P < 0.05). The values for fish fed TA₁₇ were significantly higher than for fish fed TA₁, TA₆₂ or TA₁₁₉ (P < 0.05). There were no significant differences in WG, FE or PER among fish that were fed TA₁₇ and TA₃₂, among those that were fed TA₃₂ and TA₆₂, and among those that were fed TA₆₂ and TA₁₁₉ (P > 0.05). There were also no significant differences in SGR among fish fed TA₃₂, TA₆₂ or TA₁₁₉ (P > 0.05). A broken‐line regression analysis on the basis of WG, SGR, FE and PER showed that dietary vitamin E requirements of juvenile eels were 21.2, 21.6, 21.2 and 21.5 (mg kg^?1 diet), respectively. These results indicate that the dietary vitamin E requirement could be <21.2 mg kg^?1 but <21.6 mg kg^?1 diet in juvenile eel, A. japonica, when DL‐α‐tocopheryl acetate is used as the dietary vitamin E source.     

Effect of dietary L‐malic acid supplementation on growth,feed utilization and digestive function of juvenile GIFT tilapia Oreochromis niloticus (Linnaeus, 1758)

Two feeding trials (FTs) were conducted in 2013 and 2014, respectively, to determine the optimal L‐malic acid (LMA) level for juvenile GIFT (Genetically Improved Farmed Tilapia) Oreochromis niloticus. Except for the LMA level, the FT1 and FT2 had a similar diet formulation. In FT1, LMA was included at 0 (basal diet), 1, 4, 8, 16 and 32 g kg^?1, respectively. After 20 weeks, daily weight gain and feed conversion ratio were improved but not differentiated with 1–8 g kg^?1 LMA. Further increasing the LMA supply initially decreased the feed intake (16 g kg^?1), and then decreased both feed intake and feed utilization (32 g kg^?1), thus impairing the fish growth. FT2 was subsequently conducted with a smaller LMA range (0, 0.5, 1, 2, 4 and 8 g kg^?1, respectively) but was unfortunately terminated at the end of 8 weeks because 20% of the fish were badly injured during weighing. Unexpectedly, growth and feed utilization were still improved but not differentiated with 0.5–8 g kg^?1 LMA. In FT2, beneficial effects of LMA inclusion on the digestive function (pepsin, foregut amylase and foregut lipase), the activities of serum lysozyme and hepatic superoxide dismutase, and liver lipid peroxidation (malondialdehyde concentration) were found. Taking the results of FT1 and FT2 together, it could be concluded that dietary LMA supplementation at low concentrations (0.5–8 g kg^?1) could improve growth and feed utilization, but excess LMA (≥16 g kg^?1) might compromise feed intake and/or feed utilization, thus impairing fish growth. To reduce feed costs in commercial practice, 0.5 g kg^?1 LMA is recommended in the feed of juvenile GIFT tilapia based on the results of this study.     

Effect of prebiotic mannan oligosaccharide on hematological and blood serum biochemical parameters of cultured juvenile great sturgeon (Huso huso Linnaeus, 1754)

The nutritional effects of prebiotic mannan oligosaccharide were evaluated using hematological and blood serum biochemical parameters in cultured juvenile great sturgeon (Huso huso). Fish were offered formulated diets containing two levels of prebiotic mannan oligosaccharide (2 and 4 g kg^?1); a basal diet with no prebiotics was used as control. The experiment lasted for 46 days. Blood samples were collected from the caudal veins of 18 apparently healthy fish (average weight 217.77 ± 29.8 g) at the end of the trial. No significant differences were found in the serum enzyme activity levels between treatments (P > 0.05). However, adding mannan oligosaccharide as a supplement to the basal diet resulted in significant differences in lymphocytes and eosinophils between the control and the 2 g kg^?1 treatment (P < 0.05) as well as a significant difference in the creatinine factor in the 2 g kg^?1 mannan oligosaccharide treatment (P < 0.05). The results show that it would be advantageous to add 2 g kg^?1 mannan oligosaccharide to the diets of juvenile great beluga sturgeon (Huso huso).     

Understanding the stoichiometric limitation of herbivore growth: the importance of feeding and assimilation flexibilities

Ecological stoichiometry suggests that herbivore growth is limited by phosphorus when this element in the diet is < 8.6 μg P mg C^?1 (C : P atomic ratio > 300). However, in nature, it is not necessarily related to the relative phosphorus content in diets. This may be the result of complex feeding and assimilation responses to diets. We examined these possibilities using herbivorous plankton fed mono‐specific and mixed algae varying in phosphorus content of 1.6 to 8.1 μg P mg C^?1. The herbivores showed a 10‐fold growth rate difference among the diets. Growth rates related poorly with phosphorus content in the diets (r² = 0.07), better with P ingestion rate (r² = 0.41) and best with phosphorus assimilation rate (r² = 0.69). Inclusion of assimilation rates for carbon and fatty acids increased 7% of the explained growth variance. These results indicate that the feeding and assimilation flexibilities play pivotal roles in acquiring a deficient element and in regulating growth rate.     

Liver alteration and hematological and serum biochemical responses of common carp,Cyprinus carpio Linnaeus, 1758, following long‐term feeding of pistachio (Pistacia vera) green hull extract as a source of natural phenol

This study was conducted to investigate the effect of pistachio green hull extract (PGHE) on hematological and serum biochemical changes in common carp, Cyprinus carpio. Three hundred common carp (11.65 ± 1.65 g) were fed one of five different dietary treatments (with three replications) containing 0, 0.5, 1.5, 4.5 or 9 g PGHE kg^?1diet for ten continuous weeks. Each tank had a 90‐L capacity and water flow rate of about 500 ml min^_1.Total phenolic compounds of the different diets differed significantly (P < 0.001) according to the amount of PGHE. At the end of experiment, six fish were removed randomly from each treatment. Blood samples were taken for hematological and serum biochemical analyses at room temperature. Liver tissue samples were processed for histology and stained by H&E. The results indicated that all doses of tested PGHE induced no significant changes in hematocrit, hemoglobin, or erythrocytes, nor alkaline phosphatase, alanine transaminase, lactate dehydrogenase, total protein, albumin, globulin, triglycerides, low‐density lipoprotein, high‐density lipoprotein, glucose or cholesterol in the serum. Leukocytes were higher (P < 0.01) in fish fed a 1.5, 4.5, or 9 g PGHE kg^?1 diet when compared to the 0.5 g PGHE kg^?1 diet group or the control. Serum aspartate transaminase in treatments containing a 4.5 or 9 g PGHE kg^?1 diet was significantly (P < 0.001) higher in comparison with the control. Liver histology showed focal necrosis, cytoplasm degeneration, lateral nuclei and an increase in Kupffer cells following PGHE administrations. The results of this trial indicated that although there were no significant changes in most hematological and biochemical parameters, PGHE could induce some adverse pathological effects on liver tissue.     

Antagonistic activity of two potential probiotic bacteria from fish intestines and investigation of their effects on growth performance and immune response in rainbow trout (Oncorhynchus mykiss)

The probiotic activity of two bacterial strains, Lactobacillus casei and Lactobacillus plantarum, isolated from common carp intestines was studied using antagonistic tests in vitro against Yersinia ruckeri. Randomly assigned to triplicate groups were 450 rainbow trout (mean weight, 20 ± 3 g) fed three different diets: a commercial feed, or the same feed incorporated into either 5 × 10⁷ CFU g^?1 of L. casei or L. plantarum. After a 30‐day feeding trial, 30 fish in each group were challenged with Yersinia ruckeri by intraperitoneal injection. Growth parameters were significantly increased in both treatment groups. Immune parameters such as lysozyme activity, alternative complement activity and total immunoglobulin level were significantly higher in the L. casei group than in fish fed the control diet, while no significant differences were revealed between the L. plantarum and control groups. Mortality rates of fish fed L. casei and L. plantarum were lower than in fish fed the control diet after challenging with Y. ruckeri.     

Dietary administration of chitooligosaccharides to enhance growth, innate immune response and disease resistance of Trachinotus ovatus

The present study was conducted to investigate the effects of dietary chitooligosaccharides (COS) supplementation on the innate immune response and protection against Vibrio harveyi infection in Trachinotus ovatus. A basal diet was supplemented with 0.0 (control), 2.0, 4.0 and 6.0 g COS kg^?1 to formulate four experimental diets. Each diet was randomly allocated to triplicate groups of ?sh in ?oating sea cages (1.5 × 1.0 × 2.0 m), and each cage was stocked with 80 ?sh (initial average weight 10.8 ± 0.05 g). After 8 weeks of feeding trial, Both the final weight and specific growth rate (SGR) signi?cantly increased with increasing dietary COS levels up to 4.0 g kg^?1, whereas there were no signi?cant differences for COS levels from 4.0 to 6.0 g kg^?1. A decreased feed conversion ratio (FCR) was observed with increasing dietary COS levels. The total leukocyte counts (WBC), differential leukocyte counts, respiratory burst activity, lysozyme and superoxide dismutase (SOD) activity were signi?cantly increased with the increased levels of dietary COS (P < 0.05), and reached a maximum at level of 4.0 g kg^?1 COS. There were no signi?cant differences in those immunological parameters between 4.0 and 6.0 g kg^?1 COS. Moreover, the dietary COS supplementation groups also exhibited a decrease in the cumulative symptom rates compared to the controls when challenged with V. harveyi. These results indicated that dietary intake containing COS could enhance the immune responses of fish and improve its resistance to infection by V. harveyi. Especially supplementation with 4.0 g kg^?1 COS to the fish for 56 days showed considerable improvement in the growth, survival and immune response of the fish.     

The effect of Euglena viridis on immune response of rohu, Labeo rohita (Ham.)

The study evaluated the effect of dietary doses of Euglena viridis on the immune response and disease resistance of Labeo rohita fingerlings against infection with the bacterial pathogen Aeromonas hydrophila. L. rohita fingerlings were fed with diet containing 0 (Control), 0.1 g, 0.5 g, 1.0 g Euglena powder kg⁻¹ dry diet for 90 days. Biochemical (serum total protein, albumin, globulin, albumin:globulin ratio), haematological (WBC, RBC, haemoglobin content) and immunological (superoxide anion production, lysozyme, serum bactericidal activity) parameters of fish were examined after 30, 60 and 90 days of feeding. Fish were challenged with A. hydrophila 90 days post-feeding and mortalities were recorded over 10 days post-infection. The results demonstrate that fish fed with Euglena showed increased levels of superoxide anion production, lysozyme, serum bactericidal activity, serum protein and albumin (P < 0.05) compared with the control group. Following challenge with A. hydrophila less survivability was observed in the control group (56.65%) than the group fed the experimental diets. The group fed 0.5 g Euglena kg⁻¹ dry diet showed the highest percentage survival (75%). These results indicate that Euglena stimulates the immunity and makes L. rohita more resistant to A. hydrophila infection.     

Influence of Tribulus terrestris extract on the survival and histopathology of Oreochromis mossambicus (Peters, 1852) fry before and after Streptococcus iniae infection

The aim of this study was to determine the effects of Tribulus terrestris extract (TT) on growth performance, disease resistance and histopathological changes in intestine and liver tissues of Oreochromis mossambicus (Peters, 1852) first‐feeding fry before and after exposure to Streptococcus iniae. Five isonitrogenous and isocaloric diets were formulated to contain 0 (control), 200, 400, 600, and 800 mg kg^?1 TT. After feeding for 45 days, fish were infected with S. iniae and mortalities recorded. Final weight, weight gain and SGR of tilapia fry fed the 400 mg kg^?1 TT diet were significantly greater than that of control diet. In the challenge experiment, the best survival rate was obtained with 400 mg kg^?1 TT supplementation. Infection by S. iniae appeared to have a negative effect on histopathological findings and outcome than did TT‐800 used alone. However, administration of TT (200 or 400 mg extract kg^?1) resulted in overall improvement in the intestine and liver histopathology, emphasizing the protective potential of TT. The present study suggests the protective potential of TT in alleviating intestinal and hepatic damage that can occur after a S. iniae infection. It was concluded that 400 mg kg^?1 TT can enhance growth and disease resistance during first–feeding of O. mossambicus fry. This suggests that TT may be an alternative to antibiotics in controlling streptococcal disease in tilapia culture.     

Effects of dietary xanthophylls/astaxanthin ratios on the growth and skin pigmentation of large yellow croaker Larimichthys crocea (Richardson, 1846)

An 8‐week feeding trial was conducted to evaluate the effects of dietary xanthophylls/ astaxanthin ratio on the growth and skin color of large yellow croaker, Larimichthys crocea. Five pigment‐supplemented diets were formulated to contain 75/0, 50/25, 37.5/37.5, 25/50 and 0/75 mg kg^?1 of xanthophylls/astaxanthin. The xanthophylls contain 89.31% lutein and 6.12% zeaxanthin. A diet without pigment supplementation was used as the control. The large yellow croaker juveniles (13.80 ± 0.03 g) were randomly distributed in 18 sea cages (1.0 × 1.0 × 1.5 m) at a density of 45 fish per cage. Water temperature ranged from 21 to 31°C during the feeding trial. To obtain results, the survival rate, specific growth rate, feed conversion ratio, skin redness, skin yellowness, skin lightness, skin carotenoid content and skin melanin content were measured. The results showed that the survival rate, specific growth rate and feed conversion ratio were not significantly affected by dietary treatments (P > 0.05). The ventral skin lightness was also not affected by dietary treatments (P > 0.05); however, the dorsal skin lightness of fish fed with the control diet was significantly lower than those fed with pigment‐supplemented diets (P < 0.05). The lowest values of yellowness and carotenoid content both in the ventral skin and dorsal skin were found in the control group. Yellowness and carotenoid content increased with an increasing proportion of dietary xanthophylls in both the ventral and dorsal skin. Higher redness values were found in the compound pigment groups, either in the dorsal skin or ventral skin. Fish fed with the control diet showed a higher melanin content in the dorsal skin than those fed with pigment‐supplemented diets, although differences were not significant (P > 0.05). Lightness and yellowness were linearly related to skin carotenoid content. Meanwhile, skin yellowness and carotenoid content were linearly related to the proportion of xanthophylls in dietary pigments.     

Effect of probiotic Bacillus subtilis Ch9 for grass carp,Ctenopharyngodon idella (Valenciennes, 1844), on growth performance,digestive enzyme activities and intestinal microflora

In the present study, Bacillus subtilis Ch9 was evaluated as a probiotic in grass carp, Ctenopharyngodon idella (Valenciennes, 1844). For 56 days the grass carp (50 ± 2.5 g) were given a feed containing B. subtilis Ch9 in three concentrations: 1.0 × 10⁹ (T₁), 3.0 × 10⁹ (T₂) and 5.0 × 10⁹ (T₃) CFU kg^?1 feed in triplicate treatments. The control group (T₀) was given feed without B. subtilis Ch9 for the same period. Determined were the specific growth rate (SGR), feed conversion ratio (FCR), and digestive enzyme activities in the intestine and hepatopancreas as well as the intestinal microflora. After 56 days, fish receiving the diets supplemented with B. subtilis Ch9 showed significantly higher SGR and lower FCR (P < 0.05) than those fed the control diet. There was no significant different in SGR and FCR among T₁, T₂ and T₃ nor was the survival rate affected (P > 0.05) by the dietary treatments. From days 14 to 56 of the experiment, higher protease, amylase and lipase activities in the foregut, midgut hindgut and hepatopancreas were observed in T₁, T₂ and T₃ (P < 0.05) compared with the control over a short‐term (14–28 days). Enzyme activity did not increase after long‐term feeding with B. subtilis Ch9 (56 days), but was still higher than that of control fish (P < 0.05). Fish fed the probiotic had an increase in trend of total aerobic and facultative anaerobic bacterial quantity (P > 0.05), but the ratio of Bacillus was significantly higher (P < 0.05) than in control fish. The total anaerobic bacterial quantity, Bifidobacterium and Lactobacillus were significantly higher (P < 0.05) in fish fed B. subtilis Ch9 compared with fish fed control feed. In conclusion, an optimum dose of B. subtilis Ch9 could modulate intestinal microflora, induce digestive enzyme activity and potentially promote the digestion and absorption of nutrients, as well as improve the growth performance of grass carp significantly.     

Effects of dietary thymol‐carvacrol on growth performance,hematological parameters and tissue composition of juvenile rainbow trout,Oncorhynchus mykiss

Growth performance, carcass quality, survival and hematological responses of Oncorhynchus mykiss juveniles (initial weight 8.4 ± 0.1 g) fed diets containing thymol‐carvacrol powder at the levels of 0, 1.0, 2.0, 3.0 g kg^?1 were tested. Thymol‐carvacrol powder originated from Origanum vulgare, a Mediterranean plant, added to diets. Each diet was fed to triplicate groups of fish for 45 days. Fish fed diets containing thymol‐carvacrol had significantly higher final weight and growth than the control group. Food conversion ratio in fish fed diets containing 2.0 and 3.0 g kg^?1 thymol‐carvacrol was statistically better than in other treatments. Survival was not different among all treatments. The number of lymphocytes increased when thymol‐carvacrol was used at higher levels. Furthermore, whole body lipid content was higher in fish fed 1.0 and 2.0 g kg^?1 thymol‐carvacrol than the other groups, but body protein in the group fed 3.0 g kg^?1 was higher than in other groups. Also, body ash in control and 1.0 g kg^?1 was higher than in other groups. Whole body dry matter was not affected by dietary treatments. These results indicated that dietary administration of thymol‐carvacrol can influence some growth, hematological parameters and tissue composition in rainbow trout juveniles.     

Effects of jackbean lectin (ConA) on the feeding behaviour and kinetics of intoxication of the pea aphid, Acyrthosiphon pisum

Mannose‐binding lectins were shown to be useful in creating transgenic plants resistant to insects, including many phloem‐feeding Hemiptera. Before these plants can be used extensively, it is important to understand how these lectins exert their toxic effects on the target organisms. We investigated the feeding alterations induced by presenting the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), with a diet containing the lectin from Canavalia ensiformis (ConA). A series of behavioural experiments were carried out to detect potential sensory mediation of lectin activity. Choice tests performed with a 400 µg ml^?1 ConA diet (3.7 µm of native tetramer) showed that A. pisum quickly rejected the ConA diet, but that this reaction was not typical of a sensory‐mediated phagodeterrent effect. In addition, the aphids did not develop a conditioned taste aversion to the lectin. Diet uptake was evaluated using a radioactive tracer (¹⁴C‐methylated inulin), and showed depression of ingestion only after 16 h at 200 µg ml^?1 or after 8 h at 400 µg ml^?1 ConA. This effect was reversible under our test conditions. No evidence was obtained for early detection of the lectin, even by intoxicated aphids. An electrical penetration graph technique was adapted to artificial diets and provided short‐term continuous analysis on feeding/probing events. At the 400 µg ml^?1 level, adults were affected and had reduced ingestion durations as early as in the first 4 h of contact, but experienced an adaptation to the behavioural alterations induced by lectin feeding. Overall, feeding deterrency following exposure to mannose lectins appeared to be a consequence of intoxication, and not due to a sensory mediated process.