Evaluation of l-ascorbyl-2-glucose as the source of vitamin C for juvenile Korean rockfish Sebastes schlegeli (Hilgendorf)

This study was conducted to compare l ‐ascorbyl‐2‐glucose (AA2G) with l ‐ascorbyl‐2‐monophosphate‐Na/Ca (AMP‐Na/Ca) for supplying the dietary vitamin C for juvenile Korean rockfish Sebastes schlegeli (Hilgendorf). Fish were fed one of seven semi‐purified diets containing equivalents of 0, 50, 100 and 200 mg ascorbic acid (AA) kg^?1 diet in the form of AA2G or AMP‐Na/Ca for 12 weeks. After 12 weeks of feeding, weight gain, feed efficiency ratio and survival of fish fed the vitamin C‐free diet were significantly lower than those of fish fed the vitamin C‐supplemented diets in either form. The hepatosomatic index, condition factor and survival of fish fed AMP‐Na/Ca₁₀₀, AMP‐Na/Ca₂₀₀, AA2G₁₀₀ and AA2G₂₀₀ diets were significantly higher than fish fed the vitamin C‐free diet. After 9 weeks of feeding, fish fed the vitamin C‐free diet began to show vitamin C deficiency signs such as anorexia and lethargy. At the end of the 12‐week feeding trial, fish fed the vitamin C‐free diet exhibited vitamin C deficiency signs, e.g., anorexia, scoliosis, exophthalmia and fin haemorrhage. Vitamin C retention in the muscle and liver was similar to those of fish fed AA2G‐ or AMP‐Na/Ca‐supplemented diets. In general, there was no significant difference in the muscle and liver vitamin C concen‐tration in fish fed the AA2G and AMP‐Na/Ca diets at the same supplementation levels.     

Effectiveness of l‐ascorbyl‐2‐monophosphate Na/Ca as a vitamin C source for yellowtail Seriola quinqueradiata juveniles

A feeding experiment was conducted to examine the efficacy of a vitamin C (L‐ascorbic acid, AsA) derivative, l ‐ascorbyl‐2‐monophosphate Na/Ca (AMP‐Na/Ca) by comparing to l ‐ascorbyl‐2‐monophosphate‐Mg (AMP‐Mg) in terms of growth, AsA content in tissues, and hematology in yellowtail Seriola quinqueradiata juvenile (1.10 ± 0.01 g). Furthermore, a stress resistance test for the species fed AMP‐Na/Ca was also conducted. In experiment 1, 11 test pellet diets with different levels of AMP‐Na/Ca (0, 12, 43, 88, 440 and 881 mg AsA kg^?1diet) and AMP‐Mg (0, 16, 52, 106, 595 and 1164 mg AsA kg^?1 diet) were formulated and fed to the yellowtail three times per day for 50 days. In both the vitamin C sources, the survival rates of the fish fed diets without supplemental AsA were lower than 50% at day 20, and more than 50% mortality occurred in fish that fed the diets containing 12 or 16 mg AsA kg^?1 after day 30. However, no significant differences were detected in survival and growth among fish that fed the diets containing more than 43 mg AsA kg^?1. Liver and brain AsA concentrations generally increased with increasing dietary AsA level in both sources. In experiment 2, test diets were formulated to contain 43, 88, 440 and 881 mg AsA kg^?1 using AMP‐Na/Ca, and after 60 days of feeding, yellowtail juveniles were subjected to low salinity and air exposure stress. The fish that received diets with 440 mg AsA kg^?1 showed significantly higher tolerance to low salinity stress and higher survival rate in air exposure stress than those of other groups. The present study demonstrated that yellowtail juveniles could utilize AMP‐Na/Ca as an AsA source like AMP‐Mg, and that supplementation of 43–52 mg AsA kg^?1 diet was optimum for normal growth. However, this study showed that dietary inclusion of 440 mg AsA kg^?1 would be necessary to improve stress resistance of this species.     

Dietary ascorbic acid requirement for growth of striped catfish,Pangasianodon hypophthalmus (Sauvage, 1878) juveniles

A sixty‐day feeding trial was conducted to determine the ascorbic acid (AA) requirement for growth of striped catfish, Pangasianodon hypophthalmus juveniles. Seven iso‐nitrogenous and iso‐energetic (370 g protein per kg and 19.6 MJ/kg) purified diets were prepared with different levels of ascorbic acid such as control (0), T₁ (17.5), T₂ (35), T₃ (70), T₄ (175), T₅ (350) and T₆ (700) mg ascorbic acid (L‐ascorbyl‐2‐polyphosphate) equivalent per kg diet. Fish with a mean body weight of 3.2–3.4 g were stocked (fifteen fish per tank) in triplicates following a completely randomized design. Each group was fed to satiation twice a day for 60 days. Significant differences were observed in growth, survival, body composition and metabolic enzymes activities with different dietary ascorbic acid levels. Maximum weight gain, specific growth rate (SGR) and protein efficiency ratio (PER) were found in fishes fed with 35 mg AA per kg diet, supported by best feed conversion. Fish fed a diet containing vitamin C had the highest activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) compared to those fed with vitamin C‐depleted diets. In this study, based on using broken‐line regression analysis, the dietary vitamin C requirement for growth of P. hypophthalmus juveniles was estimated to be in the range of 46–76 mg AA per kg, depending on the criterion used, growth and liver storage. Our results will be helpful for the formulation of cost‐effective ascorbic acid incorporated diets for striped catfish, P. hypophthalmus.     

Preliminary Study of the Optimum Dietary Ascorbic Acid Level in Sea Cucumber,Apostichopus japonicus (Selenka)

A 14‐wk feeding trial was carried out to evaluate the optimum dietary ascorbic acid (AA) level in juvenile sea cucumber, Apostichopus japonicus. Sea cucumbers averaging 1.49 ± 0.07 g (mean ± SD) were randomly distributed into 18 rectangular plastic tanks of 20 L capacity in a recirculating system (20 animals per tank). Six semipurified experimental diets were formulated to contain 0 (l ‐ascorbyl‐2‐monophosphate [AMP]; AMP0), 30 (AMP24), 60 (AMP48), 120 (AMP100), 240 (AMP206), and 1200 (AMP1045) mg AA/kg diet in the form of AMP using casein as the main protein source. Sea cucumbers were fed each of the six experimental diets in triplicate groups. At the end of 14 wk of feeding trial, weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) of sea cucumbers fed AMP100, AMP206, and AMP1045 were significantly (P < 0.05) higher than those of animals fed AMP0, AMP24, and AMP48. However, there were no significant differences in WG, SGR, and FE among sea cucumbers fed AMP100, AMP206, and AMP1045 and among animals fed AMP0, AMP24, and AMP48. Whole‐body vitamin C concentration increased with AA content of the diets. Broken‐line analysis of WG showed an optimum dietary AA level of 105.3 mg AA/kg diet in sea cucumber. These results indicated that the optimum dietary vitamin C level in sea cucumber in the form of AMP could be greater than 100 mg AA/kg diet but less than 105.3 mg AA/kg diet.     

Effect of dietary encapsulated organic salts (Na‐acetate,Na‐butyrate,Na‐lactate and Na‐propionate) on growth performance,haemolymph, antioxidant and digestive enzyme activities and gut microbiota of juvenile narrow clawed crayfish,Astacus leptodactylus leptodactylus Eschscholtz, 1823

A 63‐day experiment was done to study the effects of four levels (5, 10, 20 and 50 g/kg) of encapsulated organic salts (Na‐acetate, Na‐butyrate, Na‐lactate and Na‐propionate) on the growth indices and haemato‐immunological responses of crayfish Astacus leptodactylus leptodactylus (4.38 ± 0.08 g). Crayfish were distributed at 51 1,000‐L tanks (17 treatments at triplicate). The highest values of final weight (27.86 g), specific growth rate (2.94% body weight per day) and survival rate (96%) were observed in the crayfish fed the 20 g/kg of encapsulated Na‐propionate diet (p < .05). The highest activities of phenoloxidase (7.4 U/min), superoxide dismutase (7.80 U/min) and lysozyme (9.40 U/min) were observed in the gut of crayfish fed the 20 g/kg of encapsulated Na‐propionate diet (p < .05), as well as the highest activities of alkaline protease (10.70 U/mg), lipase (9.10 U/mg), amylase (9.60 U/mg) and the lactobacillus count (p < .05). Broken line regression model of SGR and phenoloxidase activity suggested that the optimum dietary levels of encapsulated Na‐acetate, Na‐butyrate, Na‐lactate and Na‐propionate could be 30.7, 31.8, 31.4 and 33.5 g/kg, respectively, in crayfish reared in culture conditions.     

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.     

Re‐evaluation of Potassium Fertilization of Bluegill,Lepomis macrochirus,Ponds

An experiment consisting of eight potassium fertilization rates ranging from 0 to 60 kg K₂O/ha was conducted in earthen ponds stocked with bluegill, Lepomis macrochirus, at Auburn University in Alabama. Each pond also received nitrogen and phosphorus fertilization at 6 kg N and 3 kg P₂O₅/ha per application. After 11 fertilizer applications for over 7 mo, potassium concentrations in pond water ranged from 3.3 mg/L in control ponds to 38.9 mg/L in the pond receiving 60 kg K₂O/ha. The coefficients of determination (R²) between potassium fertilization rate and bluegill production and between potassium concentration in pond water and bluegill production were 0.039 and 0.071, respectively. Potassium fertilization appears unnecessary in bluegill ponds where water contains more than 2 mg/L of potassium.     

Effect of algal addition on stability of fatty acids and some water‐soluble vitamins in juvenile Artemia franciscana

A minor stabilization effect was found for the content of total lipids, total fatty acids and docosahexaenoic acid (DHA) when Artemia franciscana was maintained at high concentrations of Isochrysis galbana for 72 h at 12 °C, both in 3‐ and 4‐day‐old individuals. The eicosapentaenoic (EPA) level was only stabilized at higher algal concentrations in the 4‐day‐old A. franciscana. In the 3‐day‐old A. franciscana, the EPA content increased at all algal concentrations during the first 24 h of post enrichment, presumably as an effect of DHA catabolism. Apparently, the 4‐day‐old A. franciscana metabolized DHA, and other lipids, faster than the 3‐day‐old A. franciscana did. During the 72 h incubation with I. galbana, the content of ascorbic acid (AA) in A. franciscana increased approximately to 1000–1200 μg g^–1 dry weight (DW) at algal concentrations above 3 mg C L^–1, close to AA content of the algae. The vitamin B₆ content in A. franciscana decreased from approximately 20 to 4–11 μg g^–1 DW, with highest loss rates at the higher algal concentrations. The thiamin content of A. franciscana was independent of algal concentration and remained at 20–30 μg g^–1 DW. The nutritional effects of the algal incubation on the 3‐ and 4‐day‐old A. franciscana at algal concentrations which can be used during the cultivation of Atlantic‐halibut larvae (<2 mg C L^–1) was insignificant, except for the small enrichment effect of AA already at 1 mg C L^–1. Other beneficial effects of the algae should not be ruled out, like possible effects on the microflora of A. franciscana even at algal concentrations less than 2 mg C L^–1.     

Vitamin C requirement of kuruma shrimp postlarvae, Marsupenaeus japonicus (Bate), using l-ascorbyl-2-monophosphate-Na/Ca

l ‐ascorbyl‐2‐monophosphate‐Na/Ca (AMP‐Na/Ca) was used as a vitamin C source to investigate the ascorbic acid (AsA) requirements on growth performance and stress resistance of the post‐larval kuruma shrimp, Marsupenaeus japonicus. Purified carrageenan‐microbound diets with six levels of AMP‐Na/Ca, AsA equivalent to 0, 20, 56, 87, 759 and 1697 mg kg^?1 diet were fed to triplicate groups of M. japonicus (mean initial weight 16±0.3 mg) for 30 days. The diets with AsA 0, 20 and 56 mg kg^?1 showed high cumulative mortality after 10 days of feeding. After the 30‐day trial, the shrimp fed these diets had significantly lower survival and weight gain (WG, %) than those fed the 87, 759 and 1697 mg AsA kg^?1 diets. Specific growth rate and individual dry weight showed the same pattern as WG (%). There were no significant differences in growth performance among the groups fed the AsA levels at 87, 759 and 1697 mg kg^?1 at the termination of feeding trial. Broken‐line regression analysis indicated that 91.8 mg AsA kg^?1 in the diet was the optimum for post‐larval shrimp. On the other hand, dietary level of more than 800 mg AsA kg^?1 was needed to ensure high resistance to stressful conditions such as osmotic and formalin stressors.     

Effect of Varying Protein‐to‐Energy Ratios on Growth,Nutrient Retention,Somatic Indices,and Digestive Enzyme Activities of Singhi,Heteropneustes fossilis (Bloch)

Effects of varying protein‐to‐energy (P/E) ratios on growth performance, nutrient retention, body composition, and digestive enzyme activities of Singhi, Heteropneustes fossilis (7.90 ± 0.40 g; 9.40 ± 0.20 cm) were evaluated. Six experimental diets (350_Low, 350_High, 400_Low, 400_High, 450_Low, and 450_High) in a 3 × 2 factorial design were formulated to contain three protein levels (350, 400, and 450 g/kg crude protein) and two energy levels (4.07 and 4.54 kcal/g gross energy [GE]) to provide six different dietary P/E ratios (86.1, 77, 98.3, 88, 110.6, and 99 mg protein/kcal GE). The diets were hand‐fed to triplicate groups of fish for 84 d to apparent satiation at two feeding frequencies. Live weight gain, feed conversion ratio, protein retention efficiency, energy retention efficiency, somatic indices, and digestive enzyme activities were maximized by the groups fed on 400 g/kg protein with 4.07 kcal/g GE in diet 400_Low with a P/E ratio of 98.3 mg/kcal energy. The results indicate that 400 g/kg of dietary protein and 4.07 kcal/g of dietary GE with a P/E ratio of 98.3 mg protein/kcal energy is optimum for achieving efficient growth, feed conversion, and nutrient retention in H. fossilis.     

Requirements of vitamin C (L-ascorbyl-2-monophosphate-Mg and L-ascorbyl-2-monophosphate-Na) and its effects on immune responses of grouper, Epinephelus malabaricus

An 8‐week feeding trial was conducted to evaluate two vitamin C derivatives, L‐ascorbyl‐2‐monophosphate‐Mg (C2MP‐Mg) and L‐ascorbyl‐2‐monophosphate‐Na (C2MP‐Na), to satisfy the vitamin C requirement and to test their effects on the immune responses of juvenile grouper, Epinephelus malabaricus. C2MP‐Mg and C2MP‐Na were each supplemented at 20, 50, 80, 150, 250, and 400 mg kg^?1 diet in the basal diet providing of 7, 18, 31, 51, 93, 145 mg ascorbic acid (AA) equivalent of C2MP‐Mg kg^?1 diet and 4, 10, 17, 31, 47, 77 mg ascorbic acid (AA) equivalent of C2MP‐Na kg^?1 diet, respectively. Basal diet without AA supplementation was included as control. Each diet was fed to triplicate groups of grouper (mean initial weight 3.20 ± 0.05 g). Fish fed diets supplemented with either C2MP‐Mg or C2MP‐Na had significantly (P < 0.05) greater weight gain (WG), feed efficiency and survival than those fed the unsupplemented control diet. Liver ascorbate concentrations in fish generally increased as dietary C2MP‐Mg or C2MP‐Na supplementation level increased. Haemolytic complement activity was higher in fish fed diets supplemented with 92 mg AA equivalent of C2MP‐Mg kg^?1 or 10–17 mg AA equivalent of C2MP‐Na kg^?1 than fish fed the unsupplemented control diet. Lysozyme activity was higher in fish fed ≥51 mg AA equivalent of C2MP‐Mg kg^?1 or ≥47 mg AA equivalent of C2MP‐Na kg^?1 than fish fed the unsupplemented control diet. Analysis by broken‐line regression of WG indicated that the adequate dietary vitamin C concentration from each vitamin C derivative in growing grouper is 17.9 mg AA equivalent of 2MP‐Mg kg^?1 and 8.3 mg AA equivalent of C2MP‐Na kg^?1, and it also indicated that C2MP‐Mg is about 46% as effective as C2MP‐Na in meeting the vitamin C requirement of grouper.     

DEET (N,N‐diethyl‐m‐toluamide) Toxicity to Channel Catfish,Ictalurus punctatus,Sac Fry

The combination of open facilities, moisture, and warm weather during channel catfish, Ictalurus punctatus, spawning season causes mosquito‐infestation problems. A common solution to mosquito problems in hatcheries is to use mosquito repellents applied to exposed skin and clothing. DEET (N,N‐diethyl‐m‐toluamide) is the active ingredient in most personal insect repellents. We determined the 24‐h acute toxicity of DEET to channel catfish fry. The toxicity test consisted of 10 sac fry in three replications of six concentrations (range: 157–478 μL/L) and a control. In addition to toxicity testing, a trial was conducted to determine the amount of active ingredient dispensed from two different applicators: a pump sprayer and an aerosol can. The 24‐h lethal concentration (LC₁₀) was 274 ppm, and the 24‐h LC₅₀ was 345 ppm. The concentration required to kill 50% of the organisms was above the 100 ppm threshold to be considered practically non‐toxic. The pump sprayer (98.11% active ingredient) dispensed 113.3 ± 0.57 mg (mean ± SEM) active ingredient per pump. The aerosol can (30% active ingredient) dispensed 526.8 ± 6.71 mg (mean ± standard error mean [SEM]) active ingredient per second. In hatcheries where air movement by fans is not sufficient to control mosquitoes, using insect repellent products containing DEET should be safe.     

Acute Toxicity of Ammonia and Nitrite to Painted River Prawn,Macrobrachium carcinus,Larvae

This study evaluated the toxicity of ammonia and nitrite to different larval stages of Macrobrachium carcinus. Three replicated groups of larvae in the zoea stages II, V, and VIII (hence named Z₂, Z_5, and Z₈, respectively) were exposed separately to five ammonia (5, 10, 20, 40, and 80 mg total ammonia nitrogen [TAN]/L) and six nitrite concentrations (5, 10, 20, 40, 80, and 160 mg NO₂‐N/L), plus a control treatment with no addition of ammonia and nitrite, at a salinity of 20 g/L. The ammonia LC₅₀ values at 96 h for Z₂, Z₅, and Z₈ were 8.34, 13.84, and 15.03 mg TAN/L (0.50, 0.71, and 0.92 mg NH₃‐N/L), respectively, and the nitrite LC₅₀ values at 96 h for Z₂, Z₅, and Z₈ were 3.28, 9.73, and 34.00 mg NO₂‐N/L, respectively. The estimated LC₅₀ values for NO₂‐N were lower than those for TAN in most of the stages evaluated. This observation suggests that M. carcinus larvae are more tolerant to ammonia, except at Z₈, in which larvae had a higher tolerance to nitrite. Based on the lethal concentrations at 96 h, it may be concluded that the tolerance of M. carcinus to ammonia and nitrite increases with larval development. Safe levels were estimated to be 0.834 mg TAN/L (0.05 mg NH₃‐N/L) and 0.328 mg NO₂‐N/L; therefore, efforts should be made to maintain lower concentrations of these compounds throughout the larval rearing of M. carcinus.     

Larval performance of matrinxã, Brycon amazonicus (Spix & Agassiz 1829), after maternal triiodothyronine injection or egg immersion

This study compared the larval performance of matrinxã, Brycon amazonicus, after maternal triiodothyronine (T₃) injection or egg immersion of T₃. In the first experiment, three groups of females (n=4) induced to spawning received pituitary extract (CPE) and a corn oil injection (control), or CPE plus 10 mg or 20 mg kg^?1 bw T₃ dissolved in corn oil (experimental). Larvae were sampled for body weight and length measurement at hatching (0 h) and 12, 24, 36, 48 and 60 h thereafter. Hatching time, hatching success and abnormal development were monitored. In the second experiment, fertilized eggs from four females were immersed in T₃ solutions (0, 0.01, 0.05 and 0.10 mg L^?1) and larvae were sampled at hatching (0 h) and 6, 18, 30, 42, 54, 126 and 198 h thereafter. Hatching time was not affected by either means of hormone treatment. Abnormalities decreased as the T₃ concentration increased in larvae from T₃‐treated broodfish but the number of dead larvae increased proportionally. Larvae from T₃‐injected females had higher weight from 24 h after hatching and greater length from hatching, while the weight of larvae produced from T₃‐immersed eggs changed at 198 h and length from 126 h of rearing. Both routes of T₃ administration affected the early growth of matrinxã but the effect was observed earlier when broodstock females were injected.     

Effects of fish oil with difference oxidation degree on growth performance and expression abundance of antioxidant and fat metabolism genes in orange spotted grouper,Epinephelus coioides

The present study was designed to assess the effects of fish oil with different oxidation degree on growth performance, serum biochemistry parameters and expressive abundance of oxidative stress and fat metabolism genes of orange spotted grouper Epinephelus coioides. The oxidized fish oil was conducted as follows: storage temperature: 4°C, ambient temperature (AT, [31.5 ± 3.5]°C); storage time: 45, 90, 135 days; antioxidant contents: 30 mg/kg (ethoxyquin [EQ]), 300 mg/kg Higher EQ (HEQ). According to the different treated conditions, 14 kinds of fish oil with different oxidation degree were obtained: T_F+EQ [positive control (fresh oil + EQ)], T_F (negative control [fresh oil]), T_4°C+45d+EQ, T_4°C+45d+HEQ, T_4°C+90d+EQ, T_4°C+90d+HEQ, T_4°C+135d+EQ, T_{4°C+135d+HEQ}, T_AT+45d+EQ, T_AT+45d+HEQ, T_AT+90d+EQ, T_AT+90d+HEQ, T_AT+135d+EQ, T_AT+135d+HEQ. Groupers were fed isonitrogenous and isolipidic diets containing 14 kinds of fish oil for 8 weeks, respectively. The results showed that survival, weight gain rate and thermal growth coefficient decreased as oxidation degree of dietary fish oil increased (p < 0.05). Higher serum total protein, triglyceride and glucose were observed with ascending oxidation degree of fish oil (p < 0.05). The genes expression levels of catalase, superoxide dismutase and glutathione peroxidase were up‐regulated with dietary oxidized level increasing (p < 0.05). In addition, the similar status also appeared in expression of peroxisome proliferator‐activated receptor gamma (PPARγ), hormone‐sensitive lipase (HSL) and fatty acid synthase (FAS) genes. In conclusion, the fish oil would show negative influence on the fish health until peroxide value and p‐anisidine value in oil exceed 12.96 meq/kg and 20.89. The best storage condition for fish oil is 4°C, 45 days and 30 mg/kg EQ which could keep fish oil available property to grouper.     

A single‐dose pharmacokinetic study of emamectin benzoate in cod,Gadus morhua L., held in sea water at 9 °C

The pharmacokinetic profile of the antiparasitic agent emamectin benzoate was studied in plasma after intravenous (i.v.) injection and in plasma, muscle and skin following oral (p.o.) administration to cod, Gadus morhua, held in sea water at 9 °C and weighing 100–200 g. Following i.v. injection, the plasma drug concentration‐time profile showed two distinct phases. The plasma distribution half‐life (t_1/2α) was estimated as 2.5 h, the elimination half‐life (t_1/2β) as 216 h, the total body clearance (Cl_T) as 0.0059 L kg^?1 h^?1 and mean residence time (MRT) as 385 h. The volume of distribution at steady state, V_d(ss), was calculated to be 1.839 L kg^?1. Following p.o. administration the peak plasma concentration (C_max) was 15 ng mL^?1, the time to peak plasma concentration (T_max) was 89 h and t_1/2β was 180 h. The highest concentration in muscle (21 ng g^?1) was measured after 7 days and t_1/2β was calculated to be 247 h. For skin, a peak concentration of 28 ng g^?1 at 3 days was observed and a t_1/2β of 235 h was determined. The bioavailability following p.o. administration was calculated to be 38%.     

A novel micro‐organism for removing excess ammonia‐N in seawater ponds and the effect of Cobetia amphilecti on the growth and immune parameters of Litopenaeus vannamei

To investigate the feasibility of using micro‐organisms for ammonia‐N removal, six strains were isolated from Chinese white shrimp, Fenneropenaeus chinensis, seawater culture ponds in Dongying (Shandong, China). Of these, strain DY‐01, which exhibited the highest capacity to degrade ammonia‐N, removed 61.7% of the total ammonia‐N (50 mg/L) in 8 hr. An investigation of the factors affecting the removal efficiency indicated the optimum conditions to be 30°C, pH 8.0, and a salinity level of 30 g/L; 16S rDNA gene sequencing and biochemical analysis identified strain DY‐01 as Cobetia amphilecti, which has not previously been reported to degrade ammonia‐N. This strain also boosted the growth of Pacific white shrimp, Litopenaeus vannamei (p < .05), at a concentration of 10⁷ CFU/mL, with no harmful effects on the shrimp's immune system. This study has thus identified a novel aerobic nitrifying bacterium that is potentially an excellent candidate for improving the water quality in mariculture ponds.     

Pharmacokinetics and physio‐metabolic response of single and multiple dose of fenbendazole in Labeo rohita (Hamilton, 1822) fingerlings

An experiment was carried to determine the plasma fenbendazole (FBZ) concentration and physio‐metabolic responses in juveniles of Labeo rohita (90 ± 4 g) after oral administration of single doses at 10, 20 and 50 mg, 20 mg FBZ/kg b.wt. in multiple times on 1st, 3rd and 7th day. The blood samples were collected at 0.5, 1, 2, 4, 8, 12, 24, 30, 48, 72, 96 and 120 hr, after single‐dose administration, and regularly (upto 15 day) in multiple dose. Plasma FBZ concentration was determined up to the limit of detection (LoD) of 0.09 µg/ml by HPLC. There was no parent drug detected in plasma for administration of 10 mg FBZ/kg b.wt. The drug attained the peak concentration (C_max) 1.85 and 3.09 µg/ml in plasma at 4 hr (T_max) after administration of 20 and 50mg FBZ/kg b.wt. respectively. Plasma FBZ was detectable up to 96 and 120 hr with concentration 0.09 ± 0.007 and 0.098 ± 0.006 µg/ml, respectively, after single‐dose administration of 20 and 50mg/kg b.wt. In case of multiple‐dose administration, the maximum concentration of FBZ was 1.01 ± 0.03 µg/ml on 7th day that was less than to the single dose at 50 mg/kg b.wt. However, FBZ was detected up to 11 day after multiple doses. The study revealed that the hepatic antioxidant enzymes activities like superoxide dismutase, catalase and glutathione‐S‐transferase were significantly affected by increasing FBZ in single and multiple doses. The results of the present study could reveal that single‐ or multiple‐oral administration of FBZ at 20 mg/kg b.wt. in feed as antihelminthic drug in L. rohita could be considered as the safe dose.     

Nano zinc vis‐à‐vis inorganic Zinc as feed additives: Effects on growth,activity of hepatic enzymes and non‐specific immunity in rohu,Labeo rohita (Hamilton) fingerlings

The effects of dietary administration of inorganic zinc (zinc sulphate, ZnSO₄) and nano zinc (zinc oxide nanoparticles, ZnO‐NP) were evaluated in rohu, Labeo rohita fingerlings. Fish were fed with a basal diet (Control) supplemented with ZnSO₄ (T1, T2 and T3) and ZnO‐NP (T4, T5 and T6) at 10, 20 and 30 mg/kg, respectively, for a duration of 45 days. The results revealed that fish fed diet containing 20 mg ZnO‐NP per kg (T5) had the highest weight gain and specific growth rate (SGR, % per day), which was significantly different (p < .05) from the other experimental diets. Significantly (p < .05), higher activities of the digestive and metabolic enzymes were recorded in the fish fed ZnO‐NP containing diets as compared to the diets containing inorganic Zn or control diet. The maximum serum glucose and protein levels were noted in fish reared on diet T5. Both SGOT and SGPT activities were significantly increased in fish fed Zn‐supplemented diets (T1 to T6), as compared to the control group. Similarly, innate immune parameters were improved with feeding Zn incorporated diets. The highest phagocytic (40.74 ± 0.65%) and respiratory burst (0.33 ± 0.001, OD 630nm) activities were recorded in the fish fed diet containing ZnO‐NPs at 20 mg/kg (T5). The maximum superoxide production and serum peroxidase activity were detected in the fish fed T5 and T6 diets. Overall, results indicated that short‐duration feeding (≤45 days) of dietary ZnO‐NP (20 mg/kg) improved growth, enzyme activity, serum biochemical parameters and immune function in rohu fingerlings.     

Pharmacokinetics of Florfenicol after Oral Administration in Yellow Catfish,Pelteobagrus fulvidraco

The pharmacokinetics of florfenicol (FF) and its metabolite, florfenicol amine (FFA), were investigated after doses of 10 mg/kg/day were administered orally per os (p.o.) on a single day or on three consecutive days in yellow catfish, Pelteobagrus fulvidraco, raised in water temperatures of 25 C. After a single dose p.o. was administered, the apparent volume of distribution at steady state (V_dss) of FF was computed to be 2.52 L/kg. The T_max values were in the following order: liver (1.82 h) < kidney (2.26 h) < skin (6.15 h) < muscle (6.32 h) < plasma (7.25 h). These results show that FF and FFA accumulated rapidly in the kidney and liver. The t_1/2β values in plasma, muscle, skin, liver, and kidney were 9.63, 15.75, 14.44, 11.55, and 15.75 h, respectively, for FF and 21.66, 15.07, 17.33, 26.65, and 30.13 h, respectively, for FFA. After a single p.o. dose was administered on three consecutive days, the t_1/2β values of FF and FFA in skin‐on muscle were 17.12 and 13.55 h, respectively. The total concentrations of FF and FFA in skin‐on muscle 1, 3, and 5 d after the last administration were 3.39, 0.5, and 0.062 µg/g, respectively.