UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 649 
Contribution from the States Relations Service 
A. C. TRUE, Director 
Washington, D. C. 
PROFESSIONAL PAPER 
April 13, 1918 
EXPERIMENTS ON THE DIGESTIBILITY OF FISH. 1 
By A. D. Holmes, Specialist in Charge of Digestion Experiments, Office of Home 
Economics. 
CONTENTS. 
Page. 
Introduction 1 
Digestion experiments with men 3 
Preparation of fish 4 
Nature of the diet 5 
Boston mackerel 6 
Butterfish 8 
Grayfish ' 9 
Salmon 12 
Summary 14 
INTRODUCTION. 
While many studies have been made of the digestibility of milk, 
cereals, fats, vegetables, and meats (especially beef), less information 
is available regarding the digestibility of fish. Slowzoff 2 has reported 
experiments with six persons in which fish was substituted for meat 
in an otherwise uniform diet to determine its effect on the metabolism 
of phosphorus, calcium, and magnesium. He found no change in 
the metabolism of phosphorus; the absorption of calcium was dimin- 
ished 5 per cent, and the absorption of magnesium was increased 8 
per cent. Kilanitsyn 3 found that the protein supplied by salt cod 
was 90 per cent digested by human subjects when the fish was eaten 
alone and 94.4 per cent digested when eaten as a part of a mixed diet. 
Rozov, 4 in a study of the relative digestibility of the fat of smoked 
and fresh smelt, found that it was 98 per cent utilized in the smoked 
and 97 per cent in the fresh. Slowzoff and Krawtschenko 5 report 
i Prepared under the direction of C F. Langworthy, Chief, Office of Home Economics. 
2 Verhandl. GeseU. Russ. Arzte St. Petersb., 76 (1909), p. 220. 
3 Nutritive Value of the Cod. Diss., Imp. Mil. Med. Acad. [St. Petersb.], 1887, pp. 56. [Russian.] 
* Comparative Assimilation of Fats from Fresh and Smoked Fish. Diss., Imp. Mil. Med. Acad.[ St. 
Petersb.], 1891, pp. 48. [Russian.] 
6 Verhandl. Gesell. Russ. Arzte St. Petersb., 1907-8; abs. in Zentbl. Gesam. Physiol, u. Path. Stofl- 
wechsels, n. ser., 4 (1909), No. 1, p. 40. 
Note. — This bulletin records studies of the digestibility of Boston mackerel, butterfish, grayfish, and 
salmon, and is primarily of interest to students and investigators of food problems. 
-18— Bull. 649 
