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

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

The Complete Analysis of the Distribution Kinetics of the Oxytetracycline Antibiotic in the Exoskeleton of Farmed Pacific White Shrimp,Litopenaeus vannamei

Oxytetracycline (OTC) in shrimp shells may be dispersed to the environment as shrimp shred old cuticle in growout ponds. The study aims to assess the kinetics of OTC accumulated in shrimp shell. Sub‐adult male Litopenaeus vannamei in the C–D₀ molting stage, were force fed with medicated feeds at various accurate dose levels that included 50, 500 and 1000 mg/kg‐body weight (BW). In addition to hemolymph, hepatopancreas and muscle were serially collected for 50 mg/kg‐BW‐dose group while cuticle was sampled for higher dose levels. All were assayed for OTC by a validated high‐performance liquid chromatography (HPLC) method. Mineral contents in shell samples of 500 mg/kg‐BW‐dose were also determined. The bioavailability markedly decreased with increasing dose due to incomplete dissolution and/or mild dysfunction in absorption. Administered doses, 2.69 and 2.25%, ended up in the shell after dosing with 500 and 1000 mg/kg‐BW, respectively. OTC data after a dose of 50 mg/kg‐BW was fitted into a three‐compartment model with an added shell compartment with r² of 0.9920. The model was successfully extrapolated to predict OTC distribution in shell at higher doses. In addition, there was evidence that OTC may disturb the biomineralization process via complex formation with calcium and magnesium lowering the exoskeleton mineral contents.     

Pharmacokinetics of oxolinic acid in black tiger shrimp, Penaeus monodon Fabricius, and the effect of cooking on residues

This study examined the pharmacokinetics and bioavailability of oxolinic acid (OA) in black tiger shrimp Penaeus monodon Fabricius, in brackish water (salinity 10 g L^?1) at 28–29°C, after intra‐sinus (10 mg kg^?1) and oral (50 mg kg^?1) administration and also investigated the net changes of OA residues in the shrimp after cooking (boiling, baking and frying). The haemolymph concentrations of OA after intra‐sinus dosing were best described by a two‐compartment open model. The distribution and elimination half‐lives were 0.84 and 17.7 h respectively. The apparent volume of distribution at a steady state and the total body clearance were estimated to be 2061 mL kg^?1 and 90.1 mL kg^?1 h^?1 respectively. The bioavailability of OA after an oral administration was 7.9%. The peak haemolymph concentration, the time to peak haemolymph concentration and the elimination half‐life after oral administration were 4.20 μg mL^?1, 4 h and 19.8 h respectively. Oxolinic acid muscle and shell levels increased to a maximum (muscle 1.76 μg g^?1 and shell 8.17 μg g^?1) at 4 h post administration and then decreased with the elimination half‐life value of 20.2 and 21.9 h respectively. Residual OA in muscle and shell was reduced by 20–30% by each cooking procedure examined.     

Effects of dietary selenium on the growth,selenium status,antioxidant activities,muscle composition and meat quality of blunt snout bream,Megalobrama amblycephala

An 8‐week feeding trial was performed to investigate effects of dietary selenium (sodium selenite, Na₂SeO₃; selenium nanoparticle, Nano‐Se; selenium yeast, Se‐yeast) on the growth, selenium status, antioxidant activities, muscle composition and meat quality of blunt snout bream. Na₂SeO₃ and Nano‐Se were supplemented at 0.2 mg Se kg^?1, and Se‐yeast was supplemented at 0.1, 0.2, 0.4 and 0.8 mg Se kg^?1 in basal diet; no Se was added as a control. The results indicated that groups of 0.2 and 0.4 mg kg^?1 Se‐yeast had significantly higher weight gain and Nano‐Se, 0.2, 0.4 mg kg^?1 Se‐yeast had significantly lower feed conversation ratio compared with the control group. The Se concentrations of whole body, muscle and liver linearly increased with increasing dietary Se‐yeast levels. Group of 0.4 mg kg^?1 Se‐yeast significantly increased activities of catalase and glutathione peroxidase. Muscle colour of Nano‐Se, 0.2, 0.4 mg kg^?1 Se‐yeast groups, the water‐holding capacity of 0.4, 0.8 mg kg^?1 Se‐yeast groups showed significant differences compared with the control group. The results suggest that Se‐yeast and Nano‐Se had a better growth performance than Na₂SeO₃ at 0.2 mg Se kg^?1, and supplementing appropriate Se‐yeast in diet can increase antioxidant activities and enhance meat quality of blunt snout bream.     

Hyperaccumulation of selenium in hybrid striped bass: a functional food for aquaculture?

One method of increasing the value of aquacultured product is to produce fillets that are fortified with minerals that are beneficial to human health – that is enhance the functionality of an already healthy product. A good candidate mineral in this regard is selenium (Se) which is of vital importance to normal metabolism in humans. In order to evaluate the dose response and tissue accumulation of supplemental dietary Se, a study was undertaken with hybrid striped bass (HSB). Animals were fed diets supplemented with either organic (0–3.2 mg kg^?1 as SelPlex^®) or inorganic (0.2 and 0.4 mg kg^?1 as sodium selenite) Se for 6 weeks. Because basal fishmeal‐based diets contained 1.22 mg Se kg^?1, doses of Se delivered equated to 1.22–4.42 mg kg^?1. At trial end, greatest weight gain was observed in fish receiving 0.2 mg Se kg^?1, irrespective of form (organic/inorganic). Se accumulation in HSB liver and fillet revealed a classical dose‐response once a threshold level of 0.2 mg Se kg^?1 was surpassed. Greatest tissue accumulation of Se was observed in fish fed the 3.2 mg Se kg^?1 level (P > 0.0001). A 100 g portion of Se‐enhanced HSB fillet would contain between 33 and 109 μg Se, amounting to a dietary intake of between 25 and 80 μg Se; a level that would satisfy present daily intake recommendations. Comparison of tissue Se levels indicated that the muscle provides a more conspicuous gauge of dietary Se dose‐response than does liver. Dietary treatments of between 0.4 and 1.6 mg organic Se kg^?1 reduced (P < 0.024) plasma glutathione peroxidase (GSH‐Px) activity. No differences were observed in ceruloplasmin, lysozyme or GSH‐Px activities between organic and inorganic Se when delivered at the 0.2 mg Se kg^?1 level. Ceruloplasmin, lysozyme and GSH‐Px levels were elevated (P ≥ 0.025) in fish fed the diet containing 0.4 mg inorganic Se kg^?1.     

Dietary magnesium requirement and effects on growth and tissue magnesium content of juvenile grass carp (Ctenopharyngodon idella)

A growth trial was conducted to estimate the optimum concentration of dietary magnesium (Mg) for grass carp (Ctenopharyngodon idella). Triplicate groups of grass carp (5.56 ± 0.02 g) were fed diets containing graded levels (187, 331, 473, 637, 779 and 937 mg kg^?1) of Mg for 8 weeks. Weight gain, specific growth rate and feed efficiency were linearly increased up to 637 mg kg^?1 dietary Mg and then levelled off beyond this level. For body composition, dietary Mg levels higher than 473 mg kg^?1 significantly decreased the moisture content but increased the lipid content of whole body, muscle and liver. Dietary Mg levels higher than 473 mg kg^?1 significantly decreased the ash contents of vertebrae, scales and muscle. Mg contents in whole body, vertebrae, scales and plasma were increased up to 637 mg kg^?1 dietary Mg and then levelled off beyond this level. However, Ca and P contents seem to be inversely related to dietary Mg. Dietary Mg levels higher than 473 mg kg^?1 significantly decreased Zn and Fe contents in whole body and vertebrae. Broken‐line analysis indicated that 687 mg kg^?1 dietary Mg was required for maximal tissue Mg storage, as well as satisfied for the optimal growth.     

Interactive effects of dietary vitamin C and phospholipid in micro‐bound diet for growth,survival, and stress resistance of larval red sea bream,Pagrus major

This study was conducted to examine the effects of dietary ascorbic acid (AsA) and phospholipid (PL) and their interaction on growth, survival, and stress resistance in red sea bream larvae. Twenty‐six days old red sea bream were fed nine micro‐bound diets supplemented three levels of AsA (0, 800 and 1600 mg kg^?1 diet) and PL (0, 20 and 40 g kg^?1 diet) for 15 days. Dietary AsA and PL were both significant factors on survival rates. There was also an interaction between dietary AsA and PL on survival rate (P < 0.05). The larvae fed 800 or 1600 mg kg^?1 AsA with 40 g kg^?1 PL diets showed the highest survival rate, with values similar to those of the live‐food supplemented group. Stress resistance against low salinity exposure significantly increased with increased dietary level of AsA and PL. However, significant interaction of AsA and PL was not detected. The larvae fed 1600 mg kg^?1 AsA with 40 g kg^?1 PL diet showed the highest stress resistance among all diets, but it was not significantly different than that of larvae fed 800 mg kg^?1 AsA with 40 g kg^?1 PL diet. This study clearly demonstrated that combined use of AsA and PL can improve survival of 26–40 days posthatching red sea bream larvae. Moreover, the present study suggested that 800 mg kg^?1 AsA with 40 g kg^?1 PL in diet was needed for producing high quality seedling under the stressful conditions.     

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

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

Effects of dietary vitamin E level on growth and tissue lipid peroxidation of soft-shelled turtle, Pelodiscus sinensis (Wiegmann)

A feeding trial was conducted to determine the effect of dietary vitamin E supplementation on growth, liver lipid peroxidation and liver and muscle vitamin E level of soft‐shelled turtle, Pelodiscus sinensis. Eight experimental diets analysed to contain 0–457 IU vitamin E kg^?1 were fed to juvenile soft‐shelled turtle of 4.8 g initial body weight for 12 weeks. Weight gain (WG) of the turtles fed the diet containing no vitamin E was significantly lower than those fed diets containing 83–457 IU vitamin E kg^?1 (P<0.05). Feed conversion ratio and protein efficiency ratio showed similar trends to that of WG. No significant difference (P>0.05) was found in whole‐body composition among turtles fed the different diets. Dietary vitamin E requirement using WG as the response and estimated using the broken‐line regression model is approximately 88 IU kg^?1. Liver and muscle vitamin E content increased when dietary vitamin E level increased. Ascorbate‐induced lipid peroxidation in liver tissue of turtles fed diets containing 0 and 17 IU vitamin E kg^?1 was significantly (P<0.05) greater than those fed diets containing high vitamin E (≥35 IU kg^?1).     

Palm oil-laden spent bleaching clay as a substitute for marine fish oil in the diets of Nile tilapia, Oreochromis niloticus

A 8‐week feeding trial was conducted to determine the effect of substituting fish oil with palm oil‐laden spent bleaching clay (SBC), a by‐product from crude palm oil (CPO) refining, on growth, feed utilization, fatty acid composition and heavy metal accumulation in the muscle of Nile tilapia, Oreochromis niloticus. Four isonitrogenous and isolipidic practical diets were formulated to contain 0, 100, 200 or 300 g kg^?1 SBC. Growth performance of Nile tilapia was significantly better in fish fed the 100 g kg^?1 SBC diet compared with fish fed the 0, 200 or 300 g kg^?1 SBC diet. Growth and feed utilization efficiency of fish fed 200 or 300 g kg^?1 SBC were similar to fish fed the control diet without added SBC. Whole‐body composition, body‐organ indices and haematocrit of tilapia were not affected by dietary treatments. Fatty acid compositions in the muscle lipid of Nile tilapia were strongly influenced by dietary treatments with progressively elevated levels of total saturates and n‐6 PUFA because of the dietary influence of these fatty acids from residual CPO adsorbed onto SBC. A gradual decrease in total n‐3 PUFA concentrations were also observed with the ratio of n‐3 to n‐6 fatty acids in muscle lipids decreasing from 4.75 to 4.41, 3.23 or 2.37 after 8 weeks on the 0, 100, 200 or 300 g kg^?1 SBC diet, respectively. The arsenic, cadmium and lead concentrations in the experimental diets increased with increasing dietary levels of SBC but the concentrations of these heavy metals in the whole body and bone of Nile tilapia were not significantly different among fish fed the various diets. The present 8‐week study showed that in fishmeal‐based diets for Nile tilapia, palm oil‐laden SBC can totally replace added fish oil. The use of this presently discarded waste product from palm oil refining in tilapia diets will greatly contribute to reducing the impact of rising feed costs in the culture of tilapia in many tropical countries. Other potential benefits may include acting as a feed binder, removal of mycotoxins in fish feeds as well as adsorbing toxic substances present in the culture water.     

Effect of dietary zinc level on growth,enzyme activity and body trace elements of hybrid tilapia,Oreochromis niloticus × O. aureus,fed soya bean meal‐based diets

A feeding experiment was conducted to determine the dietary zinc (Zn) requirement of hybrid tilapia fed on a diet with soya bean meal as the sole protein source. The quantity of phytic acid in the experimental diet was 15.5 g kg^?1. Juvenile hybrid tilapia were fed on diets containing 31–227 mg Zn kg^?1 in triplicates for 6 weeks. Haematology of the fish was not affected by various dietary Zn levels. Fish fed on a diet containing 31 mg kg^?1 endogenous Zn showed the lowest growth rates, feed utilization, and body and plasma Zn levels. Weight gain (WG), plasma Zn level and superoxide dismutase (SOD) activity increased when a higher quantity of dietary Zn of 127 mg kg^?1 was administered to the experimental fish. Beyond this level, the values of these parameters were relatively stable. On the other hand, within the dietary Zn range tested, whole‐body Zn and ash increased with higher dietary Zn levels. Analysis using a broken‐line model showed that the dietary Zn requirements of hybrid tilapia fed on soya bean meal‐based diets containing 15.5 g kg^?1 endogenous phytic acid were 115, 115 and 105 mg kg^?1 based on WG, whole‐body Zn retention and plasma Zn level, respectively.     

Effect of high dietary intakes of vitamin E and n-3 HUFA on immune responses and resistance to Edwardsiella tarda challenge in Japanese flounder (Paralichthys olivaceus, Temminck and Schlegel)

A feeding experiment was conducted to investigate the effects of high dietary intake of vitamin E (supplied as dl ‐α‐tocopheryl acetate) and n‐3 highly unsaturated fatty acid (n‐3 HUFA) on the non‐specific immune response and disease resistance in Japanese flounder Paralichthys olivaceus. Nine practical diets were formulated to contain one of three levels of vitamin E namely, 0, 80 or 200 mg kg^?1 (the total α‐tocopherol contents in the diets were 21, 97 and 213 mg kg^?1 based on analysis), and at each vitamin E level with one of three n‐3 HUFA levels i.e. 0.5%, 1.5% or 2.0%. Each diet was randomly assigned to triplicate groups of Japanese flounder (initial body weight: 40.5±1.0 g, mean±SD) in a re‐circulation rearing system. Fish were fed twice daily to apparent satiation at 07:00 and 18:00 hours for 12 weeks. During the experimental period, water temperature was maintained at 18±1°C, salinity 31–35 g L^?1, and pH 7.8–8.2. Dissolved oxygen was not less than 6 mg L^?1, and there were negligible levels of free ammonia and nitrite. The results showed that the increase in dietary n‐3 HUFA from 0.5% to 1.0% significantly decreased muscle α‐tocopherol contents in fish‐fed diets with 21 and 97 mg α‐tocopherol kg^?1 diet (P<0.05). In 1.0% HUFA groups, alternative complement pathway activity (ACH₅₀) of fish fed the diet containing the 213 mg α‐tocopherol kg^?1 diet was significantly higher than noted for fish fed the diet containing 97 mg α‐tocopherol kg^?1 diet (P<0.05). Fish fed the diet with 213 mg α‐tocopherol kg^?1 and 2.0% n‐3 HUFA had the highest lysozyme activity (131.7 U mL^?1) among all the dietary treatments. Fish fed the diets containing 97 and 213 mg α‐tocopherol kg^?1 with 1.0% n‐3 HUFA had significantly higher respiratory burst activity than those fed the diets containing 21 mg α‐tocopherol kg^?1 with 0.5 and 1.0% n‐3 HUFA (P<0.05). In the disease resistance experiment, high intake of dietary vitamin E with 213 mg α‐tocopherol kg^?1 significantly decreased cumulative mortality and delayed the days to first mortality after a 7‐day Edwardsiella tarda challenge (P<0.05). In addition, under the experimental conditions, dietary vitamin E and n‐3 HUFA had a synergistic effect on the non‐specific immune responses and disease resistance in Japanese flounder (P<0.05).     

Effects of dietary L‐carnitine level on growth performance,body composition and antioxidant status in beluga (Huso huso L. 1758)

A 17‐week feeding trial was carried out to evaluate the effects of dietary L‐carnitine level in beluga, Huso huso. A total of fish averaging 1247 ± 15.6 g (mean ± SD) were randomly distributed into 18 fibreglass tanks, and each tank holding 10 fish was then randomly assigned to one of three replicates of six diets with 50, 150, 350, 650, 950 and 1250 mg L‐carnitine kg^?1 diet. At the end of 17 weeks of feeding trial, average weight gain (WG), feed efficiency (FE), protein efficiency ratio (PER) and condition factor (CF) of fish fed 350 mg kg^?1 diet were significantly (P < 0.05) higher than those of fish fed 50, 150, 950 and 1250 mg kg^?1 diets. WG, FE, PER and CF of beluga fed 650 mg kg^?1 diet were also significantly higher than those of fish fed 50, 950 and 1250 mg kg^?1 diets. Whole body and muscle protein were significantly improved by the elevation of dietary L‐carnitine level up to 350 mg kg^?1. Liver superoxide dismutase and glutathione peroxidase activities of fish fed 350 and 650 mg kg^?1 diets were significantly higher than those of fish fed 50, 950 and 1250 mg kg^?1 diets. The dietary L‐carnitine level of 350–650 mg kg^?1 diet could improve growth performance, feed utilization, protein‐sparing effects of lipid, antioxidant defence system and reproductive success. Polynomial regression of WG suggested that the optimum dietary L‐carnitine level was 480 mg kg^?1 diet. Therefore, these results may indicate that the optimum dietary L‐carnitine could be higher than 350 but <650 mg kg^?1 diet in beluga reared in intensive culture conditions.     

Hepatopancreatic and muscular distribution of oxytetracycline antibiotics in farmed pacific white shrimp (Penaeus vannamei): a physiological‐based pharmacokinetic model approach

Oxytetracycline (OTC) pharmacokinetic models previously used to investigate Penaeus vannamei have not addressed the specific problems related to drug distribution/disposition in particular tissues. This study aimed to provide an insight into OTC kinetics in the hepatopancreas and muscle based on a physiological model approach. Adult male P. vannamei at the C‐D₀ inter‐moulting stage were randomly assigned to intra‐sinus and oral administrations. In the intra‐sinus group, shrimps were dosed via the ventral sinus at an OTC level of 10.0 μg g^?1 body weight, while in the oral one, they were force fed at a dose level of 50.2 μg g^?1. The medicated animals were sampled at various time intervals until 170 h after dosing. Haemolymph, muscle and hepatopancreas samples were taken and OTC levels were determined using the validated HPLC method. A model focused on the hepatopancreas and muscle was developed. Oxytetracycline pharmacokinetic profiles in particular tissues were fitted into the model with an R² of between 0.6568 and 0.9904. Oxytetracycline muscular distributions were essentially identical for both groups and the drug did not accumulate in muscle. The distributions in the hepatopancreas for both groups were extensive, whereas that for oral administration was approximately 2.3 times greater than that for the intra‐sinus one. It was demonstrated that hepatopancreatic OTC may undergo significant first‐pass elimination with non‐linear kinetics.     

Comparison of diets for the tropical spiny lobster Panulirus ornatus: astaxanthin-supplemented feeds and mussel flesh

The fast‐growing tropical lobster Panulirus ornatus is a good aquaculture candidate generating increased research to develop potential feeds. We conducted a 12‐week experiment, assessing growth, survival and tissue carotenoid levels of juvenile P. ornatus. Lobsters were fed either pelleted feeds supplemented with astaxanthin and containing 30, 60, 90 or 120 mg total carotenoid kg^?1; or one of two fresh mussel reference feeds – blue Mytilus edulis and green‐lipped Perna canaliculus. There was no clear dose response, in terms of growth rate, to increasing dietary astaxanthin content; mussel‐fed lobsters had inferior growth rates. Twelve‐week survival was unaffected by treatment. Whole lobster carotenoid (4.7, 16.7, 27.8 and 32.8 mg kg^?1, dry matter basis) increased with increasing dietary astaxanthin; pre‐treatment carotenoid was 22.2 mg kg^?1. Apparent total carotenoid content of the mussel‐fed lobsters was unexpectedly high because of interference by other pigments. High‐performance liquid chromatographic analysis of free astaxanthin levels varied from a pre‐treatment value of 7.3 mg kg^?1 to 2.0, 7.6, 12.5 and 23.6 mg kg^?1 with increasing dietary astaxanthin, and 3.5 (green‐lip) and 5.9 (blue) mg kg^?1 for the mussel‐fed lobsters. Although dietary astaxanthin, over the investigated range, did not affect growth rate or survival, there was a dose–response increase in tissue carotenoid content and darkening of the exoskeleton pigmentation, which may have important implications for immunocompetency and marketing. These implications are discussed in the context of pelleted feed development for this species.     

Estimation of dietary vitamin A requirement of juvenile soft‐shelled turtle,Pelodiscus sinensis

A feeding trial was conducted to evaluate the dietary vitamin A requirement of the soft‐shelled turtle Pelodiscus sinensis. Turtles with an approximate body weight of 6.8 g were fed diets containing 0–4.58 mg kg^?1 (15 251 IU) vitamin A (retinyl acetate) for 8 weeks. Turtles fed diets without vitamin A showed the lowest growth performance. The animals gradually gained weight when dietary vitamin A increased from 0 to 3.6 mg kg^?1. Liver vitamin A gradually increased with supplementation of dietary vitamin A of up to 2.7 mg kg^?1. Beyond this concentration, the vitamin A in the liver significantly increased. Data analysis using a polynomial regression or exponential model showed that the estimated dietary vitamin A requirement for juvenile soft‐shelled turtles based on weight gain, red blood cell count and liver vitamin A measurements was 3.48, 2.84 and 2.58 mg kg^?1, respectively.     

A Toxicokinetic Study of Oxytetracycline Antibiotics in Farmed Pacific White Shrimp,Penaeus vannamei

Toxicokinetics has demonstrated abnormal signs in drug distribution/disposition without waiting until the drug damages the tissues/organs. It is a study of the kinetic assessment of administering high‐dose of oxytetracycline (OTC) to white shrimp. Male Penaeus vannamei in the C–D₀ molting stage, were force fed with medicated feeds at various accurate dose levels including 500, 1000, and 2500 mg/kg‐body weight (BW). After dosing with different time intervals, hemolymph, muscle, and hepatopancreas were collected, and assayed for OTC by validated high‐performance liquid chromatography method. The simulated profile based on the maximum recommended dose was tested to approach the systemic level where the drug was anticipated not to cause significant toxic responses. OTC kinetic profiles in the hemolymph were fitted into the flow limited model having r² value between 0.8341 and 0.9373. The relative affinities for the muscle and hepatopancreas changed at dose level exceeding 1000 mg/kg BW. Although hepatopancreatic clearance was non‐linearly related with dose, the persistence of OTC in muscle after 2500 mg/kg BW dosing was observed to indicate abnormalities in drug distribution/disposition. It was hypothesized that the pharmacokinetic alteration after extreme dosing was because of induction of functional abnormalities in hepatopancreas. In addition, a single administration of OTC at 1000 mg/kg BW was anticipated to be a tolerated dose.     

Effects of dietary heat‐killed Lactobacillus plantarum L‐137 (HK L‐137) on the growth performance,digestive enzymes and selected non‐specific immune responses in sea cucumber,Apostichopus japonicus Selenka

A feeding trial was conducted to evaluate the efficacy of dietary heat‐killed Lactobacillus plantarum L‐137 (HK L‐137) on growth performance, digestive, non‐specific immune and phagocytosis of sea cucumber, Apostichopus japonicus. Sea cucumbers (initial body weight 1.35 ± 0.04 g) were fed diets supplemented with five levels of HK L‐137 (0, 0.005, 0.025, 0.05 and 0.25 g HK L‐137 kg^?1 diets) for 60 days. Results indicated sea cucumbers fed with diets containing 0.05 and 0.25 g HK L‐137 kg^?1 diets showed significantly (P < 0.05) higher body weight gain and specific growth rate than other groups. Sea cucumbers fed with diets containing 0.05 and 0.25 g HK L‐137 kg^?1 diets showed significantly (P < 0.05) higher protease activity than control group. Higher amylase, lysozyme and phagocytic activities were found in 0.25 g HK L‐137 kg^?1 diet group. Higher superoxide dismutase enzyme and alkaline phosphatase activity was found in 0.05 g HK L‐137 kg^?1. While no significant differences (P > 0.05) were found in acid phosphatase activity. These results suggested that dietary supplementation of 0.05 g HK L‐137 kg^?1 diets would have benefit on growth, digestive enzymes and several non‐specific immune parameters of sea cucumber.     

Dietary choline requirement for juvenile blunt snout bream,Megalobrama amblycephala

A 12‐week feeding trial was conducted to determine dietary choline requirement for juvenile Megalobrama amblycephala. The basal diet was formulated to contain 310 g kg^?1 diet from vitamin‐free casein and gelatine. Choline chloride was supplemented to the basal diet to formulate six purified diets containing 0, 250, 500, 1000, 2000 and 4000 mg kg^?1, respectively. Each diet was randomly fed to quadrupled groups of Megalobrama amblycephala with initial average weight 1.84 ± 0.04 g in a flow‐through system. Results showed weight gain was increased significantly with increasing dietary choline levels (P < 0.01). Lipid content of liver decreased significantly as dietary choline concentration increased (P < 0.01), whereas lipid content of dressed carcass showed opposite trend (P < 0.01), and lipid content of whole‐body was unaffected by dietary choline supplementation. Broken‐ line regression of weight gain, liver and muscle choline concentration showed choline requirements of Megalobrama amblycephala of 1198, 1525 and 1365 mg kg^?1, respectively. In addition, dietary choline supplementation significantly improved lipid content of dressed carcass but not the content of whole body of blunt snout bream.     

Induced spawning of Asian catfish, Clarias batrachus (Linn.): effect of various latency periods and SGnRHa and domperidone doses on spawning performance and egg quality

An experiment was conducted to induce ovulation in Asian catfish, Clarias batrachus, by a single injection of SGnRHa (d ‐Arg⁶, Trp⁷, Leu⁸, Pro⁹, Net) in combination with domperidone. The effects of latency periods, 11, 14, 17, 20 and 23 h, and doses of inducing agent, 10 μg SGnRHa+5 mg domperidone, 20 μg SGnRHa+10 mg domperidone, 30 μg SGnRHa+15 mg domperidone and 40 μg SGnRHa+20 mg domperidone kg^?1 body weight, were studied on the total egg output, stripping response, fertilization, hatching and normal larval production. The highest (P<0.05) number of eggs were stripped at 23 h of post injection of 20 μg SGnRHa+10 mg domperidone kg^?1 female body weight. The highest (P<0.05) stripping response was observed when the females were stripped at 20 and 23 h latency, at all dose levels of the inducing agent. The eggs stripped at 11 h latency did not fertilize, and hence did not hatch irrespective of administration of any dose levels of the inducing agent. The fertilization and hatching per cent of eggs had significantly increased (P<0.05) with increase in latency period to 14–23 h at a dose of 20 μg SGnRHa+10 mg domperidone. The latency period of 14–17 h, and dose of 20 μg SGnRHa+10 mg domperidone and 30 μg SGnRHa+15 mg domperidone kg^?1 of female, was found to be suitable to obtain best spawning performance, and good‐quality egg and larval production in C. batrachus.