The value of prepared food is to be Judged in the light of this fundamental principle 

 and should be adhered to in regard to the composition of all prepared foods. 



Organic Foodstuffs 



Of all the consumtd food, the organic foodstuffs come first in the order of importance. 



The organic food substances are the most important constituents of the nutrition. 

 These are first divided into the nitrogenous, albuminous, or pure protein substances; the 

 fats and oils, and the nitrogen- free extract material (principally carbohydrates). Besides 

 there are nitrogenous non-protein substances, araong which are mostly unimportant amounts of 

 completely digestible amides, all of which are added to the pure protein to make up the 

 " crude protein" . 



The almost indigestible chitin can hardly be classed among food constituents, and may 

 be classed together with plant fiber. 



Vi'ithin the metabolic cycle of fish, the proteins fulfill entirely different functions 

 from the fats and carbohydrates. The digestible proteins alone supply the necessary body 

 proteins for weight increase (growth). Neither the nitrogen-free fats and carbohydrates 

 nor the amides and chitins can produce protein. It lollovjs that the protein content in the 

 available or supplied (prepared) foodstuffs is of utmost importance. To maintain proper 

 reproductive amabolic functions, protein-rich foodstuffs are required, almost exclusively. 



If v.'e consider for a moment that reproductive anabolic needs stand to basal metabolic 

 demands in the proportion of 1:2, v.'e see at a glance that in the case of well-fed trout, the 

 proportion between digestible proteins ahd digestible nitrogen-free food constituents — the 

 so-called protein ratio -should be 1:2 at the most. 



To siii?)lify and to generalize matters, the following figures are not based upon this 

 "protein ratio" but alwaj's upon the " Sustenance ratio", namely, the ratio between all of 

 the dii^estible, nitrogenous foodstuffs (digestible crude proteins) and the nitrogen-free 

 food constituents, such as carbohydrates. 



This "sustenance ratio" in the present case, and which differs little from the "protein 

 ratio" should not amount to more than tlhjNfr eq. 1:2. (Kh: nitrogenous; Nfr: nitrogen free). 

 Such is really the ratio in the case of natural foodstuffs (aquatic aliments), where the 

 proportional rate is not higher than 1:1.8. (See table 3.) It is to be presumed that half 

 of the diet of carp consists of aquatics, with an average rJh:IIfr proportion of 1:1. Hence, 

 the remaining half of artificial food theoretically need only to have a Nh:Nfr rate of 1;5. 



If the natural nutrition, such as Chironomus. has a sustenance ratio of 1:0.5, then it 

 covers one third of the protein requisite of the total nutrition and the artificial food 

 may have an optional food ratio. A particularly high protein requirement is assumed mostly 

 in young fishes in the procesn of strong grov.-th. There are only a fen isolated exact re- 

 searches as to v/hetlier the ratio of reproductive anabolism to basal metabolism is different 

 for larger fishes. According to details given elsev*ere in this book, this is not probable. 

 In practice, liowever, younger Ege classes are frequently given relatively more protein, that 

 is, food with narrov;er sustenance ratio than with older classes. 



The following tables, 3 and ^, set forth the important total protein contents or 

 digestible crude and pure protein of foodstuffs and the "sustenance ratios" as well. 



The "sustenance ratios" v.-ere arrived at by converting the economic value of fats into 

 the respective production rate of carbohydrates (through multiplication with 2.2, as done 

 by Ke liner ) . 



In the case of aquatic food organism (insects, crabs, mollusks, etc.) and in a few 

 other isolated cases, the exact evaluation of digestible nutrient substances could not be 

 determined. Since the digestibility of the nutrient substances of food organisms is the 

 sane in all cases, we can assume that any eventual errors in these figures are negligible. 



18 



