Species specific in vitro protein digestion (pH-stat) for fish: method development and application for juvenile rainbow trout (Oncorhynchus mykiss), cobia (Rachycentron canadum), and Nile tilapia (Oreochromis niloticus).

Aqua feed manufacture requires flexible formulations and effective methods to screen suitable feed ingredients. In vitro digestion may assist in the characterization and quality control of protein in feedstuffs for fish species once standardized species-specific digestive enzyme extracts are available. This study aimed to develop a species-specific in vitro enzymatic method to assess protein digestion in fish under the pH-stat concept. Two carnivorous (rainbow trout, Oncorhynchus mykiss, and cobia, Rachycentron canadum) and one omnivorous (Nile tilapia, Oreochromis niloticus) fish species were used as models. Crude digestive enzyme extracts were recovered from stomach and pyloric caeca or intestine of individuals of different weight groups, feeding status, and farming systems. The hydrolytic capacity of the species-specific enzyme extracts was standardized on purified protein substrates and measured as degree of protein hydrolysis (DH) in the pH-stat assay. A group of twenty-four feed ingredients, including fish meals and by-products of plant and animal origin, was assessed for DH using the recovered enzymes from stomach and pyloric caeca/intestine. Ingredients were hydrolyzed with fish (i) stomach extract, (ii) pyloric caeca/intestine extract or (iii) stomach enzymes followed by pyloric caeca/intestine extract. Among plant by-products, cotton seed meal presented the highest DH with stomach plus pyloric caeca/intestine enzymes, followed by soy protein concentrate and soybean meals. Blood meals were the land animal by-product with higher DH outputs compared to poultry by-product meals and feather meals. No significant difference was observed among the DHs of fish meals. The significance of measuring the DH with stomach enzyme extract is still not well understood but, overall, the pre-hydrolysis of feedstuffs with stomach enzymes increased pyloric caeca/intestine DH value. For cage and pond farmed Nile tilapia, ingredient DHs followed the same trend, describing a significant correlation and a high determination coefficient regression. Routine use of the method may yet depend on the prompt availability of more practical sources of enzymes. The determination of the degree of protein hydrolysis by the in vitro pH-stat with species-specific enzymes has shown to be a precise method that may be a useful tool to rank feed ingredients, and also an accessory method in the quality control of feedstuffs

Early development, survival and growth rates of the giant clam Tridacna crocea (Bivalvia: Tridacnidae)

Bivalves tridacnídeos são habitantes conspícuos dos recifes da região do Indo-Pacífico e são cultivados e comercializados para os mercados alimentício e aquarista. No estudo apresentado foram determinadas as taxas de crescimento diário durante a primeira semana de vida da larva do bivalve ornamental Tridacna crocea. As matrizes foram induzidas à desova por meio de uma injeção intragonadal de serotonina realizada através do orifício bissal. Após desova, ovócitos foram coletados, fertilizados e mantidos em béqueres de vidro e tanques de fluxo contínuo tratados com antibióticos para evitar contaminação. Larvas foram alimentadas em duas ocasiões com a microalga Isochrysis galbana e zooxantelas foram oferecidas também por duas vezes. O comprimento larval foi medido através de mesa digitalizadora conectada em um microcomputador. A mortalidade larval foi exponencial durante as primeiras 48 horas de vida, diminuindo em seguida. A taxa média de crescimento foi de 11,3 μm dia-1, aumentando para 18,0 μm dia-1 após a adição de simbiontes. A sobrevivência aumentou para 75% após a adição de zooxantelas. Os resultados apresentam a curva de crescimento para a larva de T. crocea e sugerem que a aquisição de simbiontes pela larva pode ser importante para o crescimento larval e sobrevivência mesmo antes delas completarem a metamorfose.Tridacnid clams are conspicuous inhabitants of Indo-Pacific coral reefs and are traded and cultivated for the aquarium and food industries. In the present study, daily growth rates of larvae of the giant clam Tridacna crocea were determined in the laboratory during the first week of life. Adults were induced to spawn via intra-gonadal serotonin injection through the byssal orifice. After spawning oocytes were collected, fertilized and kept in 3 L glass beakers and raceways treated with antibiotics to avoid culture contamination. Larvae were fed twice with the microalga Isochrysis galbana and zooxanthellae were also offered twice during the veliger stage (days 4 and 6). Larval length was measured using a digitizing tablet coupled to a microcomputer. Larval mortality was exponential during the first 48 hours of life declining significantly afterwards. Mean growth rate was 11.3 μm day-1, increasing after addition of symbionts to 18.0 μm day-1. Survival increased to ca. 75% after the addition of zooxanthellae. The results describe the growth curve for T. crocea larvae and suggest that the acquisition of symbionts by larvae may be useful for larval growth and survival even before larvae have attained metamorphosis

Early development, survival and growth rates of the giant clam Tridacna crocea (Bivalvia: Tridacnidae)

Tridacnid clams are conspicuous inhabitants of Indo-Pacific coral reefs and are traded and cultivated for the aquarium and food industries. In the present study, daily growth rates of larvae of the giant clam Tridacna crocea were determined in the laboratory during the first week of life. Adults were induced to spawn via intra-gonadal serotonin injection through the byssal orifice. After spawning oocytes were collected, fertilized and kept in 3 L glass beakers and raceways treated with antibiotics to avoid culture contamination. Larvae were fed twice with the microalga Isochrysis galbana and zooxanthellae were also offered twice during the veliger stage (days 4 and 6). Larval length was measured using a digitizing tablet coupled to a microcomputer. Larval mortality was exponential during the first 48 hours of life declining significantly afterwards. Mean growth rate was 11.3 μm day-1, increasing after addition of symbionts to 18.0 μm day-1. Survival increased to ca. 75% after the addition of zooxanthellae. The results describe the growth curve for T. crocea larvae and suggest that the acquisition of symbionts by larvae may be useful for larval growth and survival even before larvae have attained metamorphosis

Performance of single-drain and dual-drain tanks in terms of water velocity profile and solids flushing for in vivo digestibility studies in juvenile shrimp

In vivo digestibility determination in shrimp is a challenge because these animals are coprophagous, benthic and slow feeders and the small amount of feces that they produce is difficult to collect. The objective of this study was to evaluate an efficient tank design for the purpose of studying shrimp digestibility. Different tank designs were evaluated considering drain system (dual-drain and single-drain), water inlet flow rate (8, 12, and 16 L min−1) and bottom drain diameter (6, 13, 19, 25 and 50 mm) and their effects on tank hydraulics, water velocity and solids flushing. A circular and slightly conical 500 L tank was adapted with a clarifier for the two dual-drain designs (Cornell-type and central-type) and settling columns for the two single-drain designs (Guelph-F and Guelph-L). Results showed that: (1) water rotational velocity profile was more homogeneous in tanks with larger bottom drain outlets, and water velocity increased with water inlet flow rate from almost zero up to 14.5 ± 0.7 cm s−1; (2) solids flushing, measured as the percentage of feed pellets retained at both the bottom drain and in the settling devices, was positively correlated with the surface loading rate (L min−1 flow per m2) and was more effective at the Guelph-L design fitted with a 150 mm diameter settling column. In this system 100% of the solids were removed at the inflow rate of 16 L min−1. It can be concluded that among the systems evaluated, the Guelph-L at an inflow-rate of 12 L min−1 was most efficient for both solids removal and water velocity profile and thus seemed more suitable for shrimp digestibility studies in high performance conditions. Technologies involving hydrodynamic must be intensively applied to solids removal for aquatic species production as well as research purposes like digestibility, which is highlighted in this study

Early development, survival and growth rates of the giant clam Tridacna crocea (Bivalvia: Tridacnidae)

Tridacnid clams are conspicuous inhabitants of Indo-Pacific coral reefs and are traded and cultivated for the aquarium and food industries. In the present study, daily growth rates of larvae of the giant clam Tridacna crocea were determined in the laboratory during the first week of life. Adults were induced to spawn via intra-gonadal serotonin injection through the byssal orifice. After spawning oocytes were collected, fertilized and kept in 3 L glass beakers and raceways treated with antibiotics to avoid culture contamination. Larvae were fed twice with the microalga Isochrysis galbana and zooxanthellae were also offered twice during the veliger stage (days 4 and 6). Larval length was measured using a digitizing tablet coupled to a microcomputer. Larval mortality was exponential during the first 48 hours of life declining significantly afterwards. Mean growth rate was 11.3 mu m day-1, increasing after addition of symbionts to 18.0 mu m day-1. Survival increased to ca. 75% after the addition of zooxanthellae. The results describe the growth curve for T. crocea larvae and suggest that the acquisition of symbionts by larvae may be useful for larval growth and survival even before larvae have attained metamorphosis

Responsible use of resources for\ud sustainable aquaculture

Comparisons of production, water and energy efficiencies of aquaculture\ud versus an array of fisheries and terrestrial agriculture systems show that nonfed\ud aquaculture (e.g. shellfish, seaweeds) is among the world’s most efficient\ud mass producer of plant and animal proteins. Various fed aquaculture systems\ud also match the most efficient forms of terrestrial animal husbandry, and trends\ud suggest that carnivores in the wild have been transformed in aquaculture to\ud omnivores, with impacts on resource use comparable to conventional, terrestrial\ud agriculture systems, but are more efficient. Production efficiencies of edible\ud mass for a variety of aquaculture systems are 2.5–4.5 kg dry feed/kg edible\ud mass, compared with 3.0–17.4 for a range of conventional terrestrial animal\ud production systems. Beef cattle require over 10 kg of feed to add 1 kg of edibleweight, whereas tilapia and catfish use less than 3 kg to add a kg of edible\ud weight. Energy use in unfed and low-trophic-level aquaculture systems (e.g.\ud seaweeds, mussels, carps, tilapias) is comparable to energy use in vegetable,\ud sheep and rangeland beef agriculture. Highest energy use is in fish cage and\ud shrimp aquaculture, comparable to intensive animal agriculture feedlots, and\ud extreme energy use has been reported for some of these aquaculture systems\ud in Thailand. Capture fisheries are energy intensive in comparison with pond\ud aquaculture of low-trophic-level species. For example, to produce 1 kg of catfish\ud protein about 34 kcal of fossil fuel energy is required; lobster and shrimp\ud capture fisheries use more than five times this amount of energy. Energy\ud use in intensive salmon cage aquaculture is less than in lobster and shrimp\ud fishing, but is comparable to use in intensive beef production in feedlots. Life\ud Cycle Assessment of alternative grow-out technologies for salmon aquaculture\ud in Canada has shown that for salmon cage aquaculture, feeds comprised 87\ud percent of total energy use, and fuel/electricity, 13 percent. Energy use in landbased\ud recirculating systems was completely opposite: 10 percent of the total\ud energy use was in feed and 90 percent in fossil fuel/electricity. Freshwater use\ud remains a critical issue in aquaculture. Freshwater reuse systems have low\ud consumptive use comparable to vegetable crops. Freshwater pond aquaculture\ud systems have consumptive water use comparable to pig/chicken farming and the\ud terrestrial farming of oil seed crops. Extreme water use has been documented\ud in shrimp, trout, and striped catfish operations. Water use in striped catfish\ud is of concern to Mekong policy-makers, as it is projected that these catfish\ud aquaculture systems will expand and even surpass their present growth rate to\ud reach an industry of approximately 1.5 million tonnes by 2020.\ud Water, energy and land usage in aquaculture are all interactive. Reuse and\ud cage aquaculture systems use less land and freshwater but have higher energy\ud and feed requirements, with the exception of “no feed” cage and seawater\ud (e.g. shellfish, seaweeds) systems. Currently, reuse and cage aquaculture\ud systems perform poorly in overall life cycle or other sustainability assessments\ud in comparison to pond systems. Use of alternative renewable energy systems\ud and the mobilization of alternative (non-marine) feed sources could improve the\ud sustainability of reuse and cage systems considerably in the next decade.\ud Resource use constraints on the expansion of global aquaculture are different\ud for fed and non-fed aquaculture. Over the past decade for non-fed shellfish\ud aquaculture, there has been a remarkable global convergence around the\ud notion that solutions to user (space) conflicts can be solved not only through\ud technological advances, but also by a growing global consensus that shellfish\ud aquaculture can “fit in”, not only environmentally but also in a socially\ud responsible manner, to many coastal environments worldwide, the vast majority\ud of which are already overcrowded with existing uses.\ud For fed aquaculture, new indicators of resource use have been developed and\ud promulgated. Before this resource use in fed aquaculture was being measured\ud in terms of feed conversion ratios (FCRs) followed by FIFO (“fish in fish out”)\ud ratios. First publications a decade ago measured values of FIFO in marine fish\ud and shrimp aquaculture. More comprehensive indicator assessments of fish\ud feed equivalencies, protein efficiency ratios and fish feed equivalences will allow\ud more informed decision-making on resource use and efficiencies. Over the past\ud decade, aquafeed companies have accelerated research to reduce the use of\ud marine proteins and oils in feed formulations, and have adopted indicators\ud for the production efficiencies in terms of “marine protein and oil dependency\ud ratios” for fed aquaculture species. Current projections are that over the next\ud decade, fed aquaculture will use less marine fishmeals/oils while overall\ud aquaculture production will continue its rapid growth.\ud Over the past decade, new, environmentally sound technologies and resourceefficient\ud farming systems have been developed, and new examples of the\ud integration of aquaculture into coastal area and inland watershed management\ud plans have been achieved; however, most are still at the pilot scale commercially\ud or are part of regional governance systems, and are not widespread. These\ud pilot-scale models of commercial aquaculture ecosystems are highly productive,\ud water and land efficient, and are net energy and protein producers which follow\ud design principles similar to those used in the fields of agroecology and agroecosystems.\ud Good examples exist for both temperate zone and tropical nations\ud with severe land, water and energy constraints.\ud Increasing technological efficiencies in the use of land, water, food, seed and\ud energy through sustainable intensification such as the widespread adoption\ud of integrated multi-trophic aquaculture (IMTA) and integrated agricultureaquaculture\ud farming ecosystems approaches will not be enough, since these will\ud improve only the efficiency of resource use and increase yields per unit of inputs\ud and do not address social constraints and user conflicts. In most developing\ud countries, an exponentially growing population to 2050 will require aquaculture\ud to expand rapidly into land and water areas that are currently held in common.\ud Aquaculture expansion into open-water freshwater and marine waters raises\ud the complex issues of access to and management of common pool resources,\ud and conflicts with exiting users that could cause acute social, political and\ud economic problems. The seminal works of 2009 Nobel Laureate Elinor Ostrom\ud could provide important insights for the orderly expansion of aquaculture into a\ud more crowded, resource-efficient world striving to be sustainable, and rife with\ud user conflicts

Digestive enzyme activity in juvenile Nile tilapia (Oreochromis niloticus, L) submitted to different dietary levels of shrimp protein hydrolysate

The effect of different dietary concentrations of shrimp protein hydrolysate (SPH) on digestive enzyme activity of Nile tilapia juveniles was evaluated. SPH concentrations in diets were 0, 15, 30 and 60 g kg−1 (treatments SPH0, SPH15, SPH30 and SPH60, respectively). Hemoglobin, azocasein, BApNA (Nα-benzoyl-dl-arginine-p-nitroanilide), SApNA (Suc-Ala-Ala-Pro-Phe p-nitroanilide), aminoacyl of β-naphthylamide and starch were used as substrates for enzyme activity determinations. The activity of total alkaline protease was significantly higher (P < 0.05) in fish under SPH15 and SPH60 treatments than in the control (SPH0). However, the effect was not dose-dependent. Substrate-SDS-PAGE was also performed to evaluate changes in the profile of Nile tilapia digestive proteases caused by SPH. Substrate-SDS-PAGE revealed 12 active proteolytic bands, eight of which responded to SPH dietary incorporation. Inhibition substrate-SDS-PAGE indicated a decrease in the activity of three enzymes, with trypsin activity decreasing with the increase of SPH concentration, whereas the opposite occurred for two aminopeptidases. Distinct protease profiles were also found for each treatment, suggesting adaptability of digestive proteases from Nile tilapia to the different diets.Fundação de Apoio à Ciência e Tecnologia do Estado de Pernambuco (FACEPE)FAPESP - 05/50578-2FAPESP - 07/07051-9CNPq/SEAP - 504031/03-1CNPq/SEAP - 308444/06-0CNPq/SEAP - 474222/0