Review of SEAFDEC/AQD fish nutrition and feed development research

Research on fish nutrition and feed development at SEAFDEC Aquaculture Department has focused on three major areas: nutrient requirements and their interrelationships, digestive enzymes and digestibility, and practical feed development for important species such as milkfish (Chanos chanos Forsskal), sea bass (Lates calcarifer), Nile tilapia (Oreochromis niloticus), bighead carp (Aristichthys nobilis), and tiger shrimp (Penaeus monodon). Early studies on the nutrient requirements were mainly on protein, lipid and carbohydrate. Studies on essential amino acids and fatty acids, and optimum proteln:energy ratio in the diets for cultured species were conducted later. Likewise, requirements for other essential nutrients in shrimps, like phospholipid and cholesterol, were studied. Dietary calcium and phosphorus required to prevent soft-shelled shrimps were determined. Requirements for water-soluble vitamins and bioavailability of stable forms of vitamin C were evaluated. Little is known of the vitamin and mineral requirements.The major digestive enzymes in milkfish have been studied. The apparent digestibility of common feedstuffs were determined in vivo and in vitro for milkfish and tiger shrimp, and presently, for sea bass. Development of cost-effective practical feed continues to be a major research undertaking at SEAFDEC/AQD. Diet refinement emphasizes on use of inexpensive and indigenous materials in diet formulations. The feasibility of using legumes, leaf meals, and agricultural by-products and wastes as feed components has been demonstrated. Feed and feedstuff quality control and proper processing techniques were found to improve the nutritional value of low-grade raw materials. Improved feeding techniques and practices have been pursued to minimize feeding costs. Studies on the effect of feeds on the environment are being initiated. Economically feasible grow-out diets for semi-intensive culture of milkfish, Nile tilapia, and tiger shrimp, and diets for broodstock and larvae of these species have been developed

Research on crustaceans

Crustacean research at the SEAFDEC Aquaculture Department in 1994-1999 focused on two commercially important species: the tiger shrimp Penaeus monodon, and the mud crab Scylla serrata. Research on tiger shrimp dealt with broodstock development, refinement of shrimp culture systems, and health management. Broodstock development aimed to develop a technology for a sustainable supply of good quality captive broodstock through selective breeding. Initial efforts identified polymorphic stocks with low disease prevalence as base population and development of screening protocol to assess their health status using non-lethal procedures. Improvement of reproductive performance through studies on nutritional requirements and sperm quality was also conducted. To refine shrimp culture systems, emphasis was placed on the physiological requirements of tiger shrimp, including salinity adaptation and osmoregulatory capabilities, improvement of formulated diets, and development of culture systems that are compatible with the environment. In shrimp health management, disease problems in various culture systems with emphasis on luminescent vibriosis and some viruses were defined. The quality of hatchery-reared post-larvae compared with those caught in the wild was assessed. Research on the mud crab Scylla serrata started late in 1996. Studies were conducted on all culture phases: broodstock, hatchery, nursery, and grow-out. Broodstock development emphasized the development of an appropriate maturation system and a suitable maturation diet. The influence of eyestalk ablation and dietary history on reproductive performance was assessed. The completion of the mud crab life cycle in captivity was attained in 1997 when spawns from pond-reared females were further reared to produce second-generation broodstock. In the hatchery, larval rearing based on previous trials on feeding schemes, salinity tolerance, and water conditioning hastened progress in larviculture and formed the basis for large-scale production of mud crab juveniles. Research has shown the feasibility of direct stocking of crab megalopae in hapa nets in nursery ponds. In grow-out culture, studies have been done on the effects of stocking density, monosex culture, and practical diet development for the mud crab. Practical diets, formulated using local materials as ingredients, with or without vitamin and mineral supplementation, were found to be economically feasible for mud crab culture in ponds. Grow-out culture in mangrove pens appears to be an environment-friendly alternative to the usual open pond culture system

Introduction to nutrition in tropical aquaculture

Fish is a vital component of food security especially in developing countries of the world. As the world population grows, the need for more food and more fish has correspondingly increased. Aquaculture, the farming and husbandry of fish and other aquatic organisms, is now a well-established industry worldwide and is the fastest growing food production sector. However, as aquaculture operations expand, the risk to the environment grows. Fish nutrition and feeding play important roles in the sustainable development of aquaculture. The efficient conversion of feed to fish is important to fish farmers because feed is the largest component of the total cost of production. Improved feed composition and better feed efficiency will result in higher fish production, lower feed cost, and low waste production hence, decreased nutrient load from fish farming.Feeds in aquacultureFeeds and the environmentSustainable approaches to aquacultureSummarySuggested readings</ul

The essential nutrients: Carbohydrates

This section discusses the difference among the various forms of carbohydrate and their significance in fish nutrition; distinguish between utilization of carbohydrates by warmwater and coldwater fishes and know how dietary carbohydrates are made available to fish.IntroductionClassification of carbohydratesMonosaccharidesDisaccharides and oligosaccharidesPolysaccharidesUtilization of carbohydratesGuide questions</ul

The essential nutrients: Lipids and fatty acids

The objective of this section is to acquaint the reader about common fatty acids, their nomenclature and formulas, and differentiate between saturated and unsaturated fatty acids; to know how environmental factors (temperature, salinity, diet) influence the fatty acid composition of fish; the mechanisms of fatty acid biosynthesis and oxidation, and factors that favor fatty acid biosynthesis and oxidation; the effects of lipid peroxidation and the function of antioxidants; and to understand the importance of fatty acid profiles in fish nutrition, and differences in the essential fatty acid requirements of warmwater and coldwater fishes.IntroductionTypes of lipidsGeneral function of lipidsFatty acidsStructure and classificationNomenclatureFatty acid composition of fishBiosynthesis of fatty acidsOxidation of fatty acidsLipid peroxidationImportance of fatty acid profiles in fish nutritionEssential Fatty Acid Requirements of FishGuide questions</ul

The essential nutrients: Energy

After studying this section, the reader should be able to differentiate the forms of energy and their measurement. Understand dietary energy metabolism, the energy balance equation and factors that influence dietary energy requirement of fish; and understand the significance of optimal protein to non-protein energy in fish diets.IntroductionUtilization of energyEnergy metabolismEnergy balance and dietary requirementDietary energy requirementGuide questions</ul

The essential nutrients: Vitamins

This section describes the various lipid-soluble and water-soluble vitamins, their differences, physiological functions, and the symptoms of vitamin deficiencies in fish. It also shows a summary of nutritional deficiency signs and the requirements of various fish species for vitamins.IntroductionClassification of vitaminsWater-soluble vitaminsLipid-soluble vitaminsVitamin requirements of fishGuide questions</ul

The essential nutrients: Minerals

This section discusses the macro, micro, and trace minerals; their physiologic functions; and deficiency signs and symptoms. It also gives a summary of the mineral functions and mineral requirements of fishes and shrimp.IntroductionClassification of mineralsGeneral functions of mineralsMineral availabilityMacromineralsMicromineralsMineral supplementation of practical fish dietsMineral requirements of fishGuide questionsSummarySuggested readings</ul

The essential nutrients: Proteins and amino acids

This section aims to teach the reader the ten essential amino acids required by fish and their chemical structures, distinguish between essential and non-essential amino acids; the fate of absorbed amino acids in fish; effects of deficiencies and excesses of dietary amino acids in fish diets; the procedure on how to determine the qualitative and quantitative amino acid requirements of fish; methods of evaluating protein quality; and how to determine protein requirements of some aquaculture species.IntroductionAmino acidsClassification of amino acidsEssential amino acidsNon-essential amino acidsClassification of proteinsProtein structureFate of absorbed amino acidsImportance of amino acid profiles in fish nutritionQualitative amino acid requirementsQuantitative amino acid requirementsDeficiencies and excesses of dietary amino acidsEvaluation of protein qualityProtein requirementGuide questions</ul

Organic pollution in culture water resulting from excess feed and metabolite buildup

Penaeus monodon postlarvae were subjected to increasing feed concentrations and their growth and survival rates were recorded. Measurements were made of dissolved organic matter, and ammonia and nitrite-nitrogen concentrations. Survival was highest at the lowest feeding level and decreased as feed concentration increased. It is concluded that although organic matter enriches the food supply for P. monodon postlarvae, at higher concentration levels it can pollute the culture water, which in turn leads to mass mortality of the postlarvae. Secondly, the survival rate of P. monodon postlarvae is directly related to dissolved organic matter concentration, oxygen tension, and ammonia-nitrogen concentrations in the culture water. Even at sublethal levels these adverse environmental conditions decrease the survival rate