It must also be stated that we have to distinguish between three groups of "sustenance 

 ratios" to wit: 



(1) The low ratio eq. 1:2 to 1:^ 



(2) The medium ratio eq. 1:5 to 1:6 



(3) The high ratio eq. 1:8 to ltl2 



Trout require a very low ratio, while carp tolerate a medium and even high "sustenance 

 ratio" in their food. 



Lack of proteins is just as detrimental to the well-being of fish as an excess in pro- 

 teins; it will lead to toxic conditions and especially to hyperacidity. Just as important 

 as the sufficient quantitative amount in proteins is the quality of available proteins. 

 Leguminosae and cereals — chief supplementary nutrients of carp — are especially poor in 

 concentrated proteins. They are lacking in the ami noa elds tryptophane, cystine and lysine, 

 that is, precisely in these food substances needed for protein structure in the body of 

 animals and for these reasons are indispensable for them. This is another reason for 

 supplementing the additional diet of carp with plentiful natural nutrients. There is per- 

 haps no pxu-pose in considering an incooplete protein in the nutrient ratio, if the shortage 

 can be equalized by proper admixture, because it must be theoretically without value for 

 replacement and growth metabolism* It is quite possible that mixing of animal forage flours 

 with vegetable products holds great promise in the culture of carp. 



Carbohydrates and fats perform, in general, similar functions within the fish body by 

 supplying the necessary energies for proper metabolism. They also serve for an increased 

 deposit of fats. 



These two-fold functions are performed in conformity to the "isodynamlc alimentary 

 law", whereby said functions may be likewise performed by either carbohydrates, or fats, 

 or even by proteins. 



The supply of energy (for metabolic functions) depends altogether upon the energy 



contents of foodstuffs and their possible utilization. The "energy content" is merely 



anqther word for "calories" or ccmbustlon value and will be found for all foodstuffs 

 (Including the proteins) in the acconqsanying charts. 



In table ii, the caloric value is given in kilogram-calories. In table 3, figures, 

 calculated by Geng have been used. These are somewhat lower than the figures found by 

 practical experiments. 



His figures are nevertheless still somewhat too high, since they are not based — 

 like the figures in table 4 — upon the calories of the digestible compwients exclusively and 

 since, furthermore, the calories of insufficiently oxygenated waste products, (such as 

 urea, methane, etc.) were apparently not deducted. 



19 



