48 DEPARTMENT OF GAME AND FISHERIES No. 9 



The feeding experiments outlined abov^e commenced July 10th. 1930, and 

 were concluded September 13th, 1930. It is realized that such experiments 

 should extend over a considerably longer period of time, but since rather funda- 

 mental tendencies are indicated by the outline of the work gi\'en above, the 

 results are submitted with this in mind. 



In addition to the experiments carried out by Dr. J. D. Detwiler on the 

 nutrition of speckled trout, from the viewpoint of fresh meat diets, another 

 series of experiments were performed by Dr. I. L. Chaikoff and Mr. R. D. Heard, 

 M.A., on the feeding of synthetic diets to speckled trout. A brief abstract of 

 the paper prepared by Mr. Heard is as follows: 



Two lines of investigation were adopted, in order to determine: (1) the 

 effect of feeding liver which has been fractionated by the use of solvents and 

 residues; and (2) the effect of variations of the proteins and protein content of 

 diets. 



First, with a basal diet, as described in the work of McCay, Bing and Dilley^ 

 (1927), and a fresh liver diet as two separate controls, various extracts and 

 residues of liver were added to the basal diet to form a series of diets. The 

 solvents used were ether, alcohol, and acetone. In no case was the temperature 

 of the constituents of these diets allowed to rise above body temperature (37.5°C.) 



With regard to the second method various proteins were added to the con- 

 stituents of the basal diet or some of these constituents were replaced by proteins. 

 Six different diets were tried. Before preparation, the proteins used were heated 

 for two hours at 150'C. to destroy any factor H content. 



Ten fingerlings were chosen for each experimental group, and each group 

 was confined in a separate trough 6 inches wide by 30 inches long. The water 

 was maintained at a depth of 6 inches and each trough was supplied with water 

 from a common head trough. Diets were mixed into a stiff paste with water and 

 the fish were fed four times daily, the troughs being cleaned each day. 



The results of the experiments were as follows: 



1. The basal diet when supplemented either by extracts or residues of liver 

 gave as good results as when supplemented by raw liver. In this connection 

 Mr. Heard points out: 



McCay, Dilley and CrowelF (1928) have attempted to activate a similar basal diet with 

 extracts of liver, but have observed negative results. They have concluded that factor H, the 

 agent believed to be the most active in stimulating the growth of trout, was not extracted by 

 alcohol or ether. In view of the fact that McCay and Dilley* (1927) showed this factor to be 

 thermolabile, it was considered advisable to repeat the use of these solvents in the fractionation 

 of liver and adhere more rigidly to temperature conditions. McCay, Dilley and CrowelH (1928) 

 employed a maximum temperature of 65°C. in the concentration of the extracts. No records 

 were given in regard to the effect produced by feeding the residues of the liver. 



The extract and residue preparations used in this instance were not subjected to a temperature 

 in excess of that of the body, i.e., 37.5°C. 



2. The use of the basal diet itself shows no growth. 



3. The use of the basal diet when supplemented by gelatin, egg albumin, or 

 both, shows good growth, and the activation again compares favourably with 

 that produced by raw liver and in this case can only be due to the protein. 



These experiments covered only a short period of time; and while they were 

 quite satisfactory, no definite conclusions can be reached until further work has 

 been done along similar lines. 



^McCay, Bing and Dilley, "The effect of Variations in V'itamins, Protein, Fat and Mineral 

 Matter in the Diet upon the Growth and Mortality of Eastern Brook Trout," Trans. Amer. 

 Fish. Soc, 1927. 



^McCay, Dilley and Crowell, "Growth Rates of Brook Trout Reared upon Puirfied Rations, 

 upon Drv^ Skim Milk Diets and upon Feed Combinations of Cereal Grains," 1928. 



^McCay and Dilley, Factor H in the Nutrition of Trout, Trans. Amer. Fish. Soc, 1927. 



^ McCay, Dilley and Crowell, op. cit. 



