14 BULLETIN 649, U. S. DEPARTMENT OF AGRICULTURE. 



SUMMARY. 



In the study of the digestibility of the protein and fat supplied 

 by some common varieties, fish in the form of "fish loaf" was served 

 as the major part of a simple mixed diet, which also included pota- 

 toes, crackers, fruit, sugar, and tea or coffee. The principal results 

 are summarized in the following table: 



Summary of results of all digestion experiments. 



Number of 

 experiments. 



Kind offish. 



Average 

 amount of 

 fish eaten 

 per man 

 per day. 



Digestibility 



offish 



protein. 



Digestibility 

 of fish fat. 



3 

 3 

 8 



4 



Grama. 



Mackerel . . 

 Butterfish 

 Grayfish.. 

 Salmon . . . 



448 

 471 

 440 

 355 



Per cent. 

 93.1 

 91.9 

 92.8 

 93.2 



Per cent. 



95.2 

 86.4 

 94.3 

 93.7 



On an average, the subjects ate 448 grams of Boston mackerel, 

 471 grams of butterfish, 440 grams of grayfish, and 355 grams of 

 salmon daily, which would indicate that in every case the fish was 

 eaten with relish. 



Considering the experiments as a whole, the total diet supplied on 

 an average 99 grams of protein, 60 grams of fat, and 160 grams of 

 carbohydrates daily, the fuel value being 1,576 calories. The low 

 amount of fat and of carbohydrates was due to the fact that butter 

 and similar fat were omitted and the foods other than fish loaf which 

 supplied both protein and carbohydrates, were limited in order that 

 both the fat and the protein in the diet might be contributed in as 

 large proportion as possible by the fish. 



The average coefficients of digestibility for fish proteins were: 

 Boston mackerel, 93.1 per cent; butterfish, 91.9 per cent; grayfish, 

 92.8 per cent; and salmon, 93.2 per cent. In view of the close 

 agreement, it would seem, from a dietetic standpoint, that the differ- 

 ent fishes studied would supply protein in equally available form. 



The average coefficients of digestibility of the fish fats were found to 

 be as follows: Boston mackerel, 95.2 per cent; butterfish, 86.4 per 

 cent; grayfish, 94.3 per cent; and salmon, 93.7 per cent. As these 

 figures show, the fats were well assimilated in the case of the mack- 

 erel, grayfish, and salmon, which, according to the usual custom, are 

 to be regarded as "fat fishes." Considering the experiments as a 

 whole, the very complete utilization of the protein and fat supplied 

 by the fishes studied offer additional experimental evidence that 

 fish is a very valuable food and that its extensive use in the dietary 

 is especially desirable. 



