Effect of different feed formulations on feed efficiency, gonad yield and gonad quality in the purple sea urchin Heliocidaris erythrogramma

The nutritive values of three pelleted prepared diets, based on animal (AP), vegetable (VP) and yeast protein (YP) were studied for the sea urchin Heliocidaris erythrogramma (Val.). Fresh macroalga Ulva australis was used as a natural control diet. Triplicate groups of five animals were fed one of the four diets ad libitum every second day for 85 days. Sea urchins fed pelleted feeds had significantly higher food consumption rates (dry basis) and significantly lower total and protein absorption efficiencies compared with the algal diet. The gonad yield and gonad production efficiency in sea urchins fed the natural diet were significantly higher compared with initial group (gonad yield only) and urchins fed animal and vegetable diets, but did not differ significantly from those of the animals fed the yeast diet. Percent protein and lipid in the gonads were not affected by the dietary source. The taste and smell of gonads were generally better in sea urchins collected from the wild or fed yeast and natural diets than in sea urchins fed animal and vegetable diets. The animal protein diet was the most stable in seawater while the yeast protein diet had the poorest water stability. The results of this study suggest that development of a more stable, single‐cell, protein‐based diet has a potential to promote gonad production of H. erythrogramma.     

Nutrient digestibility studies in Heteropneustes fossilis (Bloch), Clarias batrachus (Linnaeus) and C. gariepinus (Burchell)

The apparent digestibility coefficient (ADC %) for protein in catfishes, Clarias batrachus (Linnaeus) (16–18 cm; 45–50 g), C. gariepinus (Burchell) (21–22 cm; 60–65 g) and Heteropneustes fossilis (Bloch) (10–12 cm; 10–15 g) was estimated for nine feedstuffs of plant and animal origin. Fat digestibility was tested for C. batrachus and C. gariepinus, wherein the influence of feeding frequency on protein digestibility was also examined. The digestibility trials were conducted with triplicate groups of 25 fish each in 70‐L polyvinyl indoor flow‐through (1–1.5 L min^?1) circular tanks (water volume=55 L). Fish were fed to satiation daily, at 08:00 and 18:00 hours, and faecal matter was collected through slow siphoning. For studying the effect of feeding frequency, fish were fed the experimental diets at 08:00, 11:00, 14:00 and 17:00 hours. The protein digestibility of the feedstuffs varied significantly within each test species. However, the protein digestibility values for most of the ingredients tested were comparable between the three catfish species. The most efficient utilization of protein in these fishes was noted for soybean meal followed by lab‐prepared fishmeal. The lowest protein digestibility was recorded for rice bran. Similarly, the utilization of fat from the feedstuffs was also significantly different within each of the two species, C. batrachus and C. gariepinus. Fat digestibility of feed ingredients was similar between the two species. With respect to the fat, soybean meal, lab‐prepared fishmeal, full‐fat soybean meal and dried fish were more efficiently utilized, while the lowest fat digestibility was obtained for rice bran. A marked decline in protein utilization was observed in the two species where the feeding frequency was increased from two to four times a day.     

Characterization of serum and mucosal antibody responses and relative per cent survival in rainbow trout, Oncorhynchus mykiss (Walbaum), following immunization and challenge with Flavobacterium psychrophilum

Serum and mucosal antibody responses of juvenile rainbow trout, Oncorhynchus mykiss, were characterized by enzyme‐linked immunosorbent assay (ELISA) following immunization with various preparations of formalin‐killed Flavobacterium psychrophilum cells. The protective nature of these preparations was then determined by immunizing rainbow trout fry and challenging with the bacterium. Juvenile rainbow trout immunized intraperitoneally (i.p.) with formalin‐killed F. psychrophilum emulsified with Freund's complete adjuvant (FCA), and i.p. with formalin‐killed F. psychrophilum either with or without culture supernatant generated significant serum antibody responses by 6 and 9 weeks, respectively. Significant mucosal antibody responses were detected by 9 weeks only in fish immunized i.p. with killed F. psychrophilum/FCA. Following immunization and bacterial challenge of rainbow trout fry, protective immunity was conferred in F. psychrophilum/FCA and saline/FCA groups with relative per cent survival values of up to 83 and 51, respectively. Significant protection was not observed in treatment groups immunized by immersion or i.p. without adjuvant at the challenge doses tested. Results suggest that stimulation of non‐specific immune factors enhances the ability of fish to mount a protective immune response, but specific antibody appears necessary to provide near complete protection. In this study, an ELISA was developed to monitor anti‐F. psychrophilum antibody production in trout. The relationship of such responses to protective immunity suggests that future vaccination strategies against coldwater disease may require stimulation of both the innate and adaptive arms of the immune response.     

The persistence of infectivity of Tetracapsulabryosalmonae-infected water for rainbow trout, Oncorhynchus mykiss (Walbaum)

Proliferative kidney disease (PKD) is caused by the infection of susceptible salmonid fish with spores of the myxozoan Tetracapsula bryosalmonae , a parasite harboured and released by several species of bryozoans. Under natural conditions, PKD is a water-borne infection of fish, whose outcome and spatio-temporal dissemination depend on the viability of spores present in the water. In order to evaluate the duration of parasite infectivity, juvenile rainbow trout, Oncorhynchus mykiss , were exposed for 20 h to T. bryosalmonae -infected water at various times post-water collection or after different filtration procedures. When infected water was held in a temperature range of 14.5–17 °C for up to 14 days, PKD was transmitted to the fish only between 0 and 12 h post-water collection and its infectivity vanished between 12 and 24 h. Similarly, the infectivity of water passed through 25 μm but not through 1 μm mesh filters, and was lost in the material eluted from the 1 μm filtration membrane although the parasite's DNA was amplified from this material. The parasitic infectivity in water appears to be fragile and this may offer opportunities to decrease the impact of PKD in trout farms by the implementation of management procedures aimed at reducing the number of the bryozoan-holding surfaces located in the river, immediately upstream from these farms.     

Effect of culture system on the nutrition and growth performance of Pacific white shrimp Litopenaeus vannamei (Boone) fed different diets

Two 8-week feeding trials were conducted with juvenile Pacific white shrimp, Litopenaeus vannamei (Boone) to compare the growth and performance of animals fed a series of experimental and commercial pelleted shrimp and fish feeds and dietary feeding regimes within an indoor running-water culture system and an outdoor zero-water-exchange culture system. The best overall shrimp growth performance was observed for animals fed the experimental shrimp diet and all-day feeding regime under outdoor zero-water-exchange culture conditions. Final body weight and average weekly growth rate under these conditions were 2.8 and 3.4 times greater, respectively, than animals of similar size fed with the same diet under indoor running-water culture conditions. Although direct comparison between indoor and outdoor culture systems is difficult because of the lower indoor water temperatures, and consequently lower mean daily feed intake of animals, it is believed that the higher growth and feed performance of animals reared under outdoor `green-water' culture conditions was primarily due to their ability to obtain additional nutrients from food organisms endogenously produced within the zero-water-exchange culture system. The most promising features of zero-water-exchange culture systems are that they offer increased biosecurity, reduced feed costs and water use for the farmer, and by doing so provide a potential avenue of moving the shrimp culture industry along a path of greater sustainability and environmental compatibility.     

Thermal stability of carp G-actin monitored by loss of polymerization activity using an extrinsic fluorescent probe

ABSTRACT:   The thermal stability of carp G-actin was investigated by monitoring loss of actin polymerization ability. To determine the amount of native actin remaining after heat treatment, actin was labeled with a fluorescence reagent, N-(1-pyrene)iodoacetamide. The loss of polymerization ability of carp actin during heat treatment, at between 45 and 55°C, occurred faster than that of chicken actin. The inactivation rate was influenced by concentrations of ATP and Ca²⁺ in solution. With the increase of Ca²⁺ concentration, the inactivation of carp actin was markedly suppressed. Furthermore, the activation energy of the inactivation of carp actin obtained from an Arrhenius plot was similar to that of chicken actin. These results indicated that the thermal instability of carp G-actin was due to the low affinites of ATP and Ca²⁺ for carp actin described in a previous report.     

Species identification method for <Emphasis Type="Italic">Scombrops boops</Emphasis> and <Emphasis Type="Italic">Scombrops gilberti</Emphasis> based on polymerase chain reaction-restriction fragment length polymorphism analysis of mitochondrial DNA

ABSTRACT:   Gnomefish Scombrops boops and Scombrops gilberti are commercially important fishes in Japan, but these species are often confused in the markets because of their morphological similarity. To identify these two species, we performed nucleotide sequencing and restriction fragment length polymorphism (RFLP) analysis on 16S ribosomal RNA (rRNA) gene and the control region in mitochondrial DNA. Five and 12 nucleotide substitutions were observed between species in the 777-bp 16S rRNA gene and 471-bp control region, respectively. Diagnostic restriction sites for discriminating between S. boops and S. gilberti were found in the 16S rRNA gene, but not in the control region. Polymerase chain reaction (PCR)–RFLP analysis using two enzymes, Eco NI and Mva I, clearly discriminated between S. boops and S. gilberti identified by meristic characters. The PCR–RFLP analysis identified most of the 168 Scombrops young caught in the coastal waters of the Izu and Miura peninsulas as S. boops , suggesting that S. gilberti juveniles are rare in this area.     

Apparent digestibility of protein, energy, and amino acids in some selected feed ingredients for pacu Piaractus mesopotamicus

The apparent digestibility coefficients (ADCs) of amino acids (AA), protein, and energy in six feed ingredients (Brazilian fish meal, soybean meal, corn gluten meal, alcoholic yeast, corn, and wheat bran) we evaluated for pacu juveniles. In general, all ingredients showed high digestibility values for all AA, and differences among ADCs of individual amino acid were detected ( P  < 0.01). Corn gluten, soybean, and fish meals had the highest ADCs of AA. The ADCs of protein in fish meal, yeast, and corn gluten meal should not be used as AA digestibility indicators, because those showed differences up to 6.7% between the ADCs of protein and AA. All ingredients had lower ADCs of energy than corn gluten meal ( P  < 0.01). Lysine was the first limiting amino acid in fish meal, corn gluten meal, wheat bran, and corn, and the second limiting amino acid in soybean meal, as methionine was the first limiting amino acid in soybean meal and yeast. However, the soybean meal was the best quality protein source, as it had the highest digestible essential amino acid index. This demonstrated that digestible amino acid values can be used to formulate practical diets for pacu, preventing potential deficiencies or excess that might cause environmental and economic losses.