Protein and Amino Acid Requirements

Abstract

Over the past 25 years, considerable progress has been made in the study of the dietary nutrient requirements of fishes (for reviews see Cowey & Sargent, 1972, 1979; Halver, 1972; National Research Council, 1981, 1983; and Millikin, 1982). Despite some obvious similarities between fishes and other vertebrates in basic qualitative nutrient needs, the two groups have markedly different quantitative nutrient requirements. For example, the optimal dietary protein level required for maximal growth in farmed fishes is reported to be 50–300% higher than that of terrestrial farm animals (Cowey, 1975). In the main, these quantitative differences have been attributed to the carnivorous/omnivorous feeding habit of fishes and their apparent preferential use of protein over carbohydrate as a dietary energy source. However, the common expression by nutritionists (including major review authors) of nutrient requirements solely in terms of a ‘dietary percentage’ has itself limited value unless it is related to the feed intake and subsequent growth of the animal. This chapter attempts to relate the protein and amino acid requirements of fishes to the ‘growing animal’ with respect to its dietary feeding regime, developmental status, position in the aquatic food chain, and its physical environment. In addition, this chapter critically assesses the methodology employed by researchers for the measurement of nutrient requirements.