The lipid composition and biochemistry of freshwater fish.

1 The Concept of Feeding Fish.- Evolution of Aquaculture.- Necessity of Feeding Fish.- Comparison of Feeding Fish and Land Animals.- Fish Versus Farm Animals as Animal Protein in Human Diets.- Levels of Fish Culture.- 2 The Nutrients.- Energy Requirements and Sources.- Proteins and Amino Acids.- Vitamins.- Essential Lipids.- Minerals.- 3 Digestion and Metabolism.- Digestion.- Measuring Nutrient Digestibility in Fish.- Metabolism.- Rate of Metabolism (Oxygen Consumption) in Fish.- 4 Nonnutrient Diet Components.- Toxins and Antimetabolites.- Diet Additives.- Accidental Contaminants.- 5 Feed Formulation and Processing.- Formulating Fish Feeds.- Practical Feed Ingredients.- Processing Fish Feeds.- 6 Fish Feeding Experiments.- Controlled Environment Studies.- Practical Environment Studies.- 7 Practical Feeding - Channel Catfish.- Feeding Practices.- Nutritional Requirements of Channel Catfish.- Importance of Natural Foods in Catfish Ponds.- Effect of Fish Size on Feeding Responses.- Compensatory Growth in Channel Catfish.- Effects of Feed on Sensory Qualities of Processed Catfish.- Feeding Brood Fish.- 8 Practical Feeding-Tilapias.- Culture Practices.- Nutrient Requirements.- Feeds and Feeding.- 9 Practical Feeding-Salmon and Trout.- Types of Salmonid Culture.- Production of Seedstock.- General Culture Methods.- Nutrient Requirements.- Feed Formulation.- Feeding Practices.- 10 Practical Feeding-Penaeid Shrimps.- Culture Practices.- Nutrient Requirements.- Feeds and Feeding.- Practical Feeds.- 11 Practical Feeding-Eels.- Culture Methods.- Nutritional Requirements.- Feed Preparation.- Feeding Practices.- Daily Feeding Rate.- Research Needs.- 12 Practical Feeding-Crawfish.- Culture.- Feeding Behavior.- Providing Natural Foods for Crawfish.- Supplemental Feeding.- Nutrient Requirements.- Appendix A Composition of Feed Ingredients.- Appendix B Common and Scientific Names of Species.

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Nutrition and Feeding of Fish

Oxygen in its molecular state O2, is essential for many metabolic processes that are vital to aerobic life. Aerobic organisms cannot exist without oxygen, which nevertheless is inherently dangerous to their lives. Like all aerobic organisms, fish are also susceptible to the effects of reactive oxygen and have inherent and effective antioxidant defenses that are well described in the literature. This review investigates the influence of different biotic and abiotic factors (age, phylogenetic position, feeding behavior, environmental factors, oxygen, temperature, presence of xenobiotics) on antioxidant defenses in fish. Studies of antioxidant activity in fish open a number of novel research lines providing greater knowledge of fish physiology, which will benefit various aspects of fish farming and artificial production.

Antioxidant Defenses in Fish: Biotic and Abiotic Factors

Dietary lipids play important roles in the energy production processes of animal tissues and as the source of essential fatty acids (EFA). Besides these functions they do have other important dietary roles as carriers of certain non-fat nutrients, notably the fat-soluble vitamins A, D and K. Recent studies on EFA in fish have demonstrated that EFA requirements of fish differ considerably from species to species. On the other hand, the results of studies on the energy requirements of fish during recent years have indicated that in the carnivorous fish such as rainbow trout, eel, yellowtail and plaice which have limited ability to utilize carbohydrates of high mol. wt as an energy source, dietary lipids play an important role in this respect and have a sparing action on dietary protein.

Lipid nutrition in fish

The physiological role of zinc as an antioxidant.

The requirement of rainbow trout for dietary zinc was investigated by feeding them with diets containing graded levels of zinc. The results of the present study demonstrate that zinc is an essential trace element in the diet of rainbow trout, even though rearing water contains a low concentration of this element (11μg/ι). The fish fed a diet low in zinc content (lppm) showed an extremely low growth rate and high mortality. A large number of the fish on the zinc-deficient diet were found to suffer from cataracts in the eyes and erosion of the fins and of the skin. The dietary zinc levels also influenced the digestibility of protein and carbohydrate, especially that of protein. The proximate composition of the fish body and the contents of trace elements in the various organs varied according to the dietary zinc levels. Judging from the growth rate of the fish, an adequate zinc content of the diet of rainbow trout was estimated to be 15 to 30ppm.

Requirement of rainbow trout for dietary zinc.

Carp were fed on diets containing different levels of calcium and phosphorus. The rearing water contained 20ppm calcium and 0.002ppm phosphorus. The growth rate correlated positively with dietary phosphorus levels but not with calcium levels. Feeding with a low-phosphorus diet resulted in reduced growth, low feed efficiency and deformity of the head. Dietary phosphorus levels affected greatly the ash, calcium and phosphorus contents of the vertebrae. Radiography of the fish receiving a low-phosphorus diet showed an insufficient development of the bones. The available phosphorus level in a diet producing the maximal growth was found to be 0.6 to 0.7%.

Mineral requirements in fish. III. Calcium and phosphorus requirements in carp.

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Requirement of chum salmon held in freshwater for dietary phosphorus.

The relationships between dietary energy sources and the utilization of dietary proteins have been investigated with rainbow trout and carp. In rainbow trout, lipid was utilized more effectively than carbohydrate (α-starch and dextrin) as an energy source for utilization of dietary protein. The values for PER and NPU of casein at low protein levels were markedly different according to the kind of energy sources used. Accordingly, the protein level producing the maximum growth rate also differed according to the main energy sources used. On the other hand, carp utilized carbohydrate effectively as an energy source.

Protein nutrition in fish. VI. Effects of dietary energy sources on the utilization of proteins by rainbow trout and carp.

Requirement of rainbow trout for essential fatty acids (EFA) was examined by feeding diets containing different levels of methyl linolenate. The shortage of EFA resulted in poor growth and low feed conversion. Methyl linolenate was superior to methyl linoleate in both enhancing growth and improving feed conversion. A diet containing 5% methyl laurate elevated the level of eicosatrienoic acid (20:3ω9) in the body lipids, while it was depressed by dietary linoleate and linolenate. Methyl linoleate elevated levels of 20:4ω6 and 22:5ω6 acids in polar lipids of the liver and methyl linolenate that of 22:6ω3 acid. From growth, feed conversion, the ratio of 20:3ω9/22:6ω3 in the polar lipids of liver and histological observation, the requirement of rainbow trout for methyl linolenate was judged to be between 0.83 and 1.66% in diet.

Chinkichi Ogino

Papers

Requirement of rainbow trout for dietary zinc.

Mineral requirements in fish. III. Calcium and phosphorus requirements in carp.

Requirement of chum salmon held in freshwater for dietary phosphorus.

Protein nutrition in fish. VI. Effects of dietary energy sources on the utilization of proteins by rainbow trout and carp.

Requirement of Rainbow Trout fot Essential Fatty Acids