MILLIKIN: NUTRIKNT REQUIRKMKNTS OF FISHES 



of the two fish species (Cowey etal. 1970). Forma- 

 tion of radioactive labelled aspartic acid, glu- 

 tamic acid, cysteine, serine, glycine, alanine, and 

 proline over a 6-d period implied that sufficient 

 amounts of these amino acids can be produced by 

 underyearling plaice and sole through inter- 

 mediary metabolism, thus suggesting dietary 

 nonessentiality of those specific amino acids. On 

 the other hand, arginine, histidine, isoleucine, 

 leucine, lysine, methionine, phenylalanine, thre- 

 onine, and valine were not incorporated from (U - 

 14 C) - glucose, thus implying dietary essentiality. 

 Although the authors suggested that metabolic 

 requirements for tyrosine were provided from 

 hydroxylation of ingested phenylalanine, this 

 still needs to be tested. Possible essentiality of 

 tryptophan was not examined, thereby leaving 

 the status of this amino acid unresolved for the 

 plaice and sole. 



Quantitative amino acid requirements deter- 

 mined for several fish species are generally based 

 on weight gain, feed efficiency, and sometimes 

 free amino acid plasma levels of individuals fed 

 graded concentrations of a particular amino acid 

 (Table 3). In addition to those values listed in 

 Table 3, coho salmon have been shown to require 

 2.4% arginine of the dry diet (6.0% of the dietary 

 protein), 0.7% histidine of the dry diet (1.7% of the 

 dietary protein) (Klein and Halver 1970), and 

 0.2% tryptophan of the dry diet (0.5% of dietary 

 protein) (Halver 1965). Many similarities exist 

 between species in individual quantitative amino 

 acid requirements when expressed as a percent 

 of dietary protein (Table 3). 



Amino acid composition of eggs and larval 

 stages for a given species has been shown to be a 



good guideline for estimating quantitative amino 

 acid requirements of fry and fingerling stages. 

 For example, diets formulated to contain the 

 amino acid composition of Atlantic salmon eggs 

 promoted better growth of Atlantic salmon fin- 

 gerlings than use of an amino acid pattern based 

 on the National Research Council's (1973) recom- 

 mendations for salmonids (Ketola 1980). Ketola 

 (1980) also observed the same pattern of acceler- 

 ated growth in rainbow trout fry fed diets formu- 

 lated on the basis of egg amino acid composition 

 of that species compared with the National Re- 

 search Council's (1973) recommendations. In a 

 separate study, rainbow trout fingerlings were 

 fed a diet containing soybean meal as the sole 

 protein source or the same diet supplemented 

 with amino acids (leucine, methionine, lysine, 

 valine, and threonine) to provide a dietary essen- 

 tial amino acid profile similar to rainbow trout 

 eggs. Improved weight gain occurred in rainbow 

 trout fingerlings fed the amino acid supple- 

 mented diet, thereby suggesting the similarity 

 between amino acid profiles of rainbow trout 

 eggs and dietary amino acid requirements of 

 rainbow trout fingerlings (Rumsey and Ketola 

 1975). 



Amino Acid Availability 



A significant contribution to channel catfish 

 diet formulation recently came from an exten- 

 sive investigation of true amino acid availability 

 (corrected for metabolic fecal amino acids) and 

 apparent amino acid availability (digestibility) 

 values of various feedstuffs commonly incorpo- 

 rated into commercial catfish diets (Wilson et al. 



Table 3.— Quantitative dietary amino acid requirements for several fish species. 



'Expressed as percentage of dietary protein with requirement as percentage of dry diet in parentheses. 



2 Based upon 24% dietary protein (Robinson et al. 1980a) 



3 Based upon 40% dietary protein unless otherwise noted (National Research Council 1973). 



4 Based upon 37.7% dietary protein (Nose and Arai Unpubl. data, cited in Cowey and Sargent 1979) 



5 Based upon 38 5% dietary protein (Nose 1979) 



6 Based upon 41% dietary protein (National Research Council 1973) 



7 ln the absence of cystine which can replace 50 to 60% of methionine requirement (Harding et al. 1977). 



'Methionine + cystine. 



9 ln the absence of cystine. 



'"Phenylalanine + tyrosine requirement. Tyrosine can replace ca. 50% of phenylalanine (Robinson 

 et al. 1980a). 



"in the absence of tyrosine. 



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