Publisher Summary
This chapter discusses the amino acids and protein requirements of fish. Proteins are the major organic material in fish tissue, making up about 65–75% of the total on a dry-weight basis. Fish consume protein to obtain amino acids. A regular intake of protein or amino acids is required because amino acids are used continually by the fish, either to build new proteins (as during growth and reproduction) or to replace existing proteins (maintenance). Inadequate protein in the diet results in a reduction or cessation of growth and a loss of weight due to withdrawal of protein from less vital tissues to maintain the functions of more vital tissues. Fish, like other animals, do not have a true protein requirement but have a requirement for a well-balanced mixture of essential or indispensable and nonessential or dispensable amino acids. Size and age, water temperature, and maintenance requirements affect the protein requirements of fishes. Various investigators have observed improved growth and feed efficiency when experimental diets for salmonids were supplemented with indispensable amino acids to simulate levels found in isolated fish protein or the respective eggs and whole-body tissue of the species being studied. The indispensable amino acid requirements of certain fish have also been shown to correlate well with the indispensable amino acid pattern of the whole-body tissue of that fish.

Amino acids and proteins

To date, aquatic feeds have depended heavily on fishmeal and fish oil as their source of protein and lipid. However, the feed industry is encountering shortfalls in the availability of these ingredients because of a decline in the number of fish captured in the wild and the increased human demand for some of the species currently being used for fishmeal and oil production. Therefore, efforts are now being directed in different parts of the world to finding alternative quality ingredients, which ideally are less expensive and readily available for use in practical diets. The data accrued have shown that a large proportion of both fishmeal and fish oil can be replaced by other protein and lipid sources. However, it is emphasized that an optimal essential amino acid balance be maintained and that the n-3 highly unsaturated fatty acid requirement be satisfied when combining economical protein and lipid ingredients. Newly developed feeds should aim at being nutrient-dense in order to reduce the output of solid, P and N waste. This can be done through improving nutrient availability, optimizing the digestible protein to energy balance of the diet, and replacing dietary fishmeal with alternate ingredients. These diets should also be effective for maintaining good health and improving disease resistance in fish through enhancement of immune responses. A wholesome approach to culturing fish would be to use appropriate feeding standards that are aimed not only at improving economic returns but also at developing a lasting cohabitation of sustainable aquaculture and a cleaner environment. Furthermore, in the 2lst century aquaculture would still retain its place as a prominent source of food protein, signifying that fish feed research remains a forceful area in discovering better feeds for the industry.

https://www.jstage.jst.go.jp/article/fishsci1994/68/2/68_2_242/_pdf

Strategies for further development of aquatic feeds.

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Nutrient Requirements Of Fish

Tentative qualitative and quantitative amino acid requirements have been reported for the major species of fish reared for market or as replacement stocks for natural waters. Most work has concentrated upon juvenile fish or upon rapidly growing young market fish; these have high protein dietary requirements (30-50%) that are in direct contrast to the homothermic terrestial animals. Net protein utilization from the diet is similar or slightly better than that found in avian species, but energy needs are much lower in fish and as a result the body protein deposition in fish is larger (about 5 g protein/MJ for the chick versus about 10 g protein/MJ for young fish). Qualitative amino acid requirements appear identical for all fish species examined; arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine are all required for normal growth and metabolism. Quantitative requirements differ only slightly among species that have been tested. Salmon have higher arginine requirements than other fish examined. Catfish appear to have a lower requirement for histidine and threonine, and the Japanese eel seems to need more tryptophan in the diet. However, when the quantitative requirements for indispensable amino acids are expressed as a percentage of the protein fed, then a remarkable harmony appears between values needed for maximal growth for most species examined. A review of Tables 3 and 4 will disclose the paucity of information available considering the large number of fish species reared commercially over the world. Most commercial diet formulations have relied upon the work done on salmon, catfish, and carp, and their amino acid and protein requirement values have been used. Remarkably, these diets have produced other species of fish economically. Sparing effects of one amino acid on another have only been studied with cystine-methionine and tyrosine-phenylalanine. Arginine and analogues of methionine have been used as good nitrogen sources for salmon. Isoleucine-leucine ratios have been measured and experiments indicate some growth inhibition when the isoleucine-leucine ratio was greater than 2/1. Valine at abnormally high levels also inhibited growth. Much more work needs to be done on the effects of subtle differences in amino acid ratios in the diet, and major emphasis should be placed on the important role of the dispensable amino acids in fish nutrition.(ABSTRACT TRUNCATED AT 400 WORDS)

Protein and Amino Acid Requirements of Fishes

Optimal dietary lipid level for growth of juvenile hybrid tilapia, Oreochromis niloticus X Oreochromis aureus

Feeding experiments were conducted twice, Experiments I and II, in order to determine an optimum dietary protein level for Tilapia nilotica by feeding them with casein diets containing corn oil as a lipid source.Daily feed consumption was found to be affected by dietary protein or cellulose levels. With an increase in the amount of dietary protein, feed consumption decreased, thus the growth rate was better in the fish fed on the diet containing 30% protein than those fed on the 40% protein diet.Effect of dietary cellulose levels on the feed consumption was great in the case of low protein diets. The best growth rate was obtained in the fish receiving the 30% protein diet, when its digestible energy (DE) level was sufficient for the fish. The amount of DE and nitrogen intake required for their maximum growth is estimated to be around 12-13 kcal and 160-170mg/l00g body weight/day, respectively.

Effect of dietary protein levels on growth of Tilapia nilotica.

This experiment was conducted to determine the relationship between dietary protein levels and feeding rates, apparent digestibility of nutrient and an optimum ratio of digestible energy (DE) to protein (P) in the diet by feeding Tilapia nilotica with diets containing various levels of DE and protein.The results showed that the optimum ratio of DE/P was 140-150, and that an optimum dietary protein level required for the maximum growth was 25%, when the feeding rate was 3.5% of fish body weight per day.Apparent digestibility of dietary protein, carbohydrate and lipid in Tilapia nilotica was higher than 90%. But, feed consumption together with apparent digestibility of carbohydrate was decreased with increase of dietary cellulose levels.The dietary DE for Tilapia calculated by using values of 4.5, 4.0 and 9.0 kcal/g for respectively protein, carbohydrate and lipid based upon digestibility of these nutrients'was found to be almost the same as those determined by the direct method.

Optimum protein and digestible energy levels in diets for Tilapia nilotica.

Feeding experiments were conducted twice in practical culture scale to develop practical carp diets which are effective to reduce nitrogen excretion from carp without reduction of growth, feed effciency and increase of feed cost. For this purpose, the experimcntal diets were propared by using locally available low cost ingredients and fed to carp in net cages in Lake Kasumigaura. Results of two experiments suggested that dietary protein level could be reduced from 39% of the official standard for carp feeds in Japan to 30-35% by elevating energy level with carbo-hydrate such as wheat flour or with lipid such as beef tallow. The use of practical ingredients in these experiments resulted in reduction of feed cost. The most suitable protein and digestible energy levels in diets for carp cultured in Lake Kasumigaura to reduce N excretion are suggested to be about 35% and 350 kcal/100g diet. Total nitrogen excretion per ton of carp production was reduced by 22 to 36% of the value from commercial diets with CP above 39% by feeding these low protein-high energy diets.

Development of practical carp diets for reduction of total nitrogen loading on water environment

Modulation of the growth performance, body composition and nonspecific immunity of white shrimps (Penaeus vannamei) upon dietary Clanis bilineata larvae

Ki-Wei Wang

Papers

Effect of dietary protein levels on growth of Tilapia nilotica.

Optimum protein and digestible energy levels in diets for Tilapia nilotica.

Development of practical carp diets for reduction of total nitrogen loading on water environment

Modulation of the growth performance, body composition and nonspecific immunity of white shrimps (Penaeus vannamei) upon dietary Clanis bilineata larvae