Ofelia S. Reyes

Requirements of juvenile marine shrimp, Penaeus monodon (Fabricius) for lysine and arginine

Abstract Feeding experiments were conducted using amino acid test diets to determine the dietary requirements of juvenile Penaeus monodon for lysine and arginine. Two sets of the test diets were prepared. The natural protein was supplied by casein and gelatin. Crystalline l -amino acids were added to provide an amino acid profile similar to shrimp muscle protein except for the test amino acid. One set of experimental diets contained graded levels of lysine at 1.18–3.28% of the diet and another set contained arginine at 0.6–3.0% of the diet. The amino acid mixture was pre-coated with carboxymethylcellulose (CMC) and diets were further bound with CMC, cornstarch, and K–carrageenan to prevent leaching losses of amino acids. Shrimp postlarvae, PL20, with mean weight of 21±0.5 mg, were randomly distributed at 10 shrimp per tank in 40-l fiberglass tanks and reared on the diets for 50–56 days. Growth, survival and feed conversion efficiency were determined at termination of feeding trials and signs of nutritional deficiency noted. Lysine and arginine requirements were determined from relationships between weight gains and dietary lysine and arginine levels as analyzed by the broken-line regression method. The requirement of juvenile P. monodon for lysine was estimated to be 2.08% of the diet or 5.2% of dietary protein while the requirement for arginine was 1.85% of the diet or 5.3% of dietary protein. This information is crucial in formulating cost-effective practical diets for juvenile tiger shrimp.

Optimum dietary protein level for growth of bighead carp (Aristichthys nobilis) fry in a static water system

Abstract Isocalric diets (290 kcal digestible energy/100 g) with protein levels ranging from 20 to 50% in increments of 5% were fed to bighead carp fry (3.8±0.2 mg mean body weight and 9.8±0.1 mm total length) for 7 weeks. Growth in weight and length increased as the protein level of the diet increased from 20 to 30% and decreased as the protein level increased further. Although not significantly different (P>0.05) from those of fry fed the 25% or 35% protein diet, weight gain (250 mg) and increase in total length (15.7 mm) were highest for fry fed the 30% protein diet. Feed conversion ratio, protein efficiency ratio and survival rate did not clearly indicate the required protein level. The protein requirement was determined using a static-water culture system but assessment of the water quality failed to indicate an association between ammonia concentration and protein in the diet. Further research is necessary to determine why high levels of protein resulted in depressed growth.

Threonine requirement of juvenile marine shrimp Penaeus monodon

The threonine requirement was determined for juvenile marine shrimp. Penaeus monodon postlarvae, PL20, were stocked in 30-1 fiberglass tanks at ten shrimp per tank arranged in a completely randomized design with six replicates per treatment. They were fed amino acid test diets (40% protein) with casein-gelatin as natural protein sources and supplemented with crystalline L-amino acids to simulate the amino acid profile of shrimp muscle except for threonine. Graded levels of threonine were incorporated to obtain 0.72, 1.0, 1.28, 1.56, 1.84, and 2.12 g per 100 g diet or 1.8, 2.5, 3.2, 3.9, 4.6, and 5.3% of dietary protein. Relationship of weight gain with dietary threonine level was analyzed by the quadratic regression method to derive the threonine requirement. Results showed that the quantitative threonine requirement for growth is 1.4% of the diet or 3.5% of dietary protein. This requirement for growth conforms with the threonine level in the shrimp muscle.

Reproductive performance and growth of Nile tilapia (Oreochromis niloticus) broodstock fed diets containing Leucaena leucocephala leaf meal

The effects of dietary leucaena leaf meal on reproductive performance and growth of Nile tilapia were determined. In the preliminary trial, sexually mature Nile tilapia were fed with a control diet or a test diet which had leucaena leaf meal as the only protein source for 24 weeks. Fish fed with the leucaena diet lost some weight and had significantly low (P 0.05). However, growth of males fed with the 80% leucaena diet was remarkably low. Fry production was highest for those fed with the control diet and the 20% leucaena diet. Fry production decreased slightly in fish fed with the 40% leucaena diet and was significantly low (P<0.05) for those fed with the 80% leucaena diet. The low fry production was preceded by a decrease in body weight of the female fish. However, the gonadosomatic indices of the females and the males were not markedly affected by the diets. On the basis of both fry production and growth, leucaena leaf meal should not exceed 40% of the diet of Nile tilapia broodstock.

Protective immunity against viral nervous necrosis (VNN) in brown-marbled grouper (Epinephelus fuscogutattus) following vaccination with inactivated betanodavirus

Viral nervous necrosis (VNN) caused by betanodaviruses has been recently implicated in serious mortalities of groupers in the grow-out culture system. A safe and effective vaccine against this disease is urgently needed. This study demonstrates that a single intramuscular vaccination with formalin-inactivated Philippine strain of piscine betanodavirus (genotype: redspotted grouper nervous necrosis virus; RGNNV) induces potent immune responses and substantial protective immunity against an intramuscular challenge with the homologous virus in brown-marbled grouper, Epinephelus fuscogutattus, a highly susceptible marine fish species to VNN. Seroneutralization assay conducted on sera of vaccinated fish revealed the occurrence of substantial neutralizing-antibody titers from Days 15 (mean titer 1:800) to 190 (1:400) with the highest titer observed at Day 60 post-vaccination (1:5120). When vaccinated fish were challenged with the homologous virus at Days 15, 30 and 75 post-vaccination, significantly higher survival rates were obtained in these fish compared with their corresponding controls (L-15 injected fish). Abrogation of virus multiplication in all vaccinated survivors was indicated by undetectable virus titers in the brains and kidneys paralleled by significantly high levels of neutralizing antibodies in the sera of these fish. Consecutively, replicates of vaccinated fish that survived betanodavirus challenge at Days 15 and 75 post-vaccination were maintained in flow-through aquaria and rechallenged with the homologous virus 3 and 5 months later, respectively. A significant drop in neutralizing-antibody titers of 3 and 8 folds, respectively, were observed in the sera of Days 15 and 75 post-vaccinated fish assayed before the virus rechallenge. Interestingly, reversion in the levels of neutralizing antibodies to significantly high levels (8-15 folds) were noted in these fish after the virus rechallenge. Taken together, our current data clearly demonstrate that a single administration of the inactivated Philippine strain of betanodavirus vaccine can effectively mount a specific anamnestic response and concomitant long-term protection against VNN in grouper at the grow-out culture system.

Influence of feeding rate and diet form on growth and survival of Nile tilapia (Oreochromis niloticus) fry

Young Nile tilapia (12 mg mean body weight and 11 mm total length) were stocked at a density of 5 fish/l in twelve 50-l aquaria filled with 30 l of tap water. They were fed pellet crumbles containing 35% crude protein at various daily feeding rates expressed as percentages of fish biomass. Mean increases in body weight after 5 weeks were 63, 198, 232 and 228 mg for the 15, 30, 45 and 60% feeding rates, respectively, when ambient temperature ranged from 19 to 21°C. Corresponding survival rates were 53, 85, 87 and 84%. Growth and survival rates were enhanced significantly (P < 0.01) at the 30, 45 and 60% feeding rates. Two feeding trials were conducted to compare the growth and survival of fry fed pellet crumbles and an unpelleted form of the same diet. Results showed that growth and feed conversion were similar for both forms of diet. However, the survival rate of fry fed pellet crumbles was significantly higher (P < 0.01) than the survival rate of fry fed the unpelleted diet. Prior pelleting of the formulated diet for the tilapia fry given at 30% to 45% of fish biomass daily ensured high survival, fast growth and efficient feed conversion.

Milkfish (Chanos chanos) fingerling production in freshwater ponds with the use of natural and artificial feeds

Abstract Milkfish fry were reared to fingerling size in freshwater ponds. For the first experiment, fish were fed the blue-green algae Oscillatoria inoculated and grown in the ponds, Oscillatoria supplemented with a fishmeal-based formulated diet, and the formulated diet alone. Twelve 50-m 2 earthen ponds were prepared to enhance growth of the indigenous natural foods. Acclimated wild milkfish fry were stocked randomly at 90/m 2 and were fed for 6 weeks. Milkfish fed the formulated diet alone had a significantly higher ( P Oscillatoria and formulated diet (0.882±0.230 g). Growth was lowest for fish fed Oscillatoria alone. The feeding treatments in the second experiment were: combination of Spirulina powder and formulated diet, formulated diet alone, and rice bran alone. The stocking rate was equivalent to 91.5–92.5 fry/m 2 and feeding lasted for 7 weeks. All feeds promoted some growth but the milkfish fed the formulated diet alone invariably had the highest weight increment (1.504±0.167 g), followed by fish given the feed combination (0.881±0.140 g). Rice bran alone gave the lowest growth response. For both pond experiments, growth trends of the young milkfish were similar to those grown under laboratory conditions. Although survival rates were significantly different in one aquarium experiment, survival rates of milkfish in ponds did not differ significantly ( P >0.05) among treatments.

Immunization regimen in Asian sea bass (Lates calcarifer) broodfish: A practical strategy to control vertical transmission of nervous necrosis virus during seed production

Outbreaks of viral nervous necrosis (VNN) in Asian sea bass (Lates calcarifer) at the larval stages via vertical transmission of nervous necrosis virus (NNV) from asymptomatic broodfish remain as a major deterrent during seed production. A five-year study was conducted to produce NNV-specific-free sea bass broodfish reared in land-based tanks through an annual immunization regimen with the formalin-inactivated NNV. We primarily immunized (intraperitoneal injection) sea bass juveniles (5 g) and monitored the neutralizing antibody (Nab) titers in the sera of these fish at scheduled intervals post-immunization. Nab titers in the sera of immunized fish peaked at Month 2 (titer: 1:4480 ± 1185) but thereafter gradually declined and significantly dropped (1:260 ± 83) at Month 12 post-primary immunization. Booster immunization of these fish at Month 12 post-immunization led to abrupt increases in Nab titers in booster immunized (B-Im) fish at Month 1 (1:12800 ± 6704) but thereafter declined and dropped at Month 12 (1:480 ± 165) post-booster immunization. The annual booster injections with the inactivated vaccine or L-15 (Unimmunized [U-Im]) were consecutively conducted for 4 years until the fish became sexually mature. Mature fish from both groups were successively induced to spawn twice (1-month interval) via intramuscular injection with luteinizing hormone-releasing hormone analogue (LHRH-a; 100 µg/kg BW). NNV was not detected by RT-PCR in oocytes and milts, and spawned eggs of B-Im fish. In contrast, oocytes and milts, and spawned eggs of U-Im fish were NNV positive. Spawned eggs of B-Im broodfish exhibited Nab titers ranging from 1:192 ± 34 to 1:240 while such was not detected (<1:40) in eggs of U-Im fish. Taken together, current data clearly demonstrate that annual immunization regimen with inactivated NNV vaccine is a pragmatic approach for sustaining immunocompetent sea bass broodfish reared in land-based tanks and circumvent the risk of vertical transmission of NNV from asymptomatic broodfish to their offspring under stress of repetitive spawning.