44 American Fisheries Society 



FEEDING COOKED BEEF HEART. 



In the practical feeding of fish in hatcheries, the question is 

 frequently asked, "shall the food be fed raw or cooked?" The 

 objection to cooked food on the ground that it is not the natural 

 condition of the fishes' nourishment, may well be dispensed with. 

 Feeding fish in hatcheries is a problem in domestication, and the 

 merits of a dietary system must be judged not by whether it resem- 

 bles or deviates from the state of things in nature, that is, wild 

 nature, but by the results which can actually be achieved with it. 

 To anticipate what will be brought out in the description of the 

 following experiments, cooked food is neither more nor less utilized 

 than the raw food, though possibly it has less growth-promoting 

 quality. For one thing it is not as palatable to the fish as the raw 

 food, and in my experience, the trout ate it much less willingly and 

 in smaller amounts. In only one respect does feeding of cooked 

 food present a decided advantage. On raw food the feces are 

 gelatinous and fairly massive, while those resulting from cooked 

 food are more or less dry and scanty. The feces therefore have no 

 tendency to adhere to the sides of the aquaria, being in well 

 formed compact masses. Contamination of the water was, there- 

 fore, never observed when cooked food was fed, and it remained 

 remarkably clear for a number of days. 



The food was put up as before, except that it was brought to a 

 quick boil with a small volume of water, the fluid completely 

 drawn off, and the meat packed in stock jars, refrigerated and 

 analyzed as usual. 



Experiment 00.2 was made on the same trout which served in 

 experiment 000.5. The result of these two experiments are, 

 therefore, well suited for comparison. The animal was fed on the 

 cooked beef heart for a considerable time to get it thoroughly 

 accustomed to this food before the actual metabolic study was 

 begun. The trout did not relish cooked food, and at best would 

 eat only small quantities. In the thirty-eight days which this 

 experiment lasted, the trout consumed only 23.9 grams of the 

 food; the feces for this period contained 51.9 mg. nitrogen and 

 34. mg. of fat. These two constituents of the diet were therefore 

 utilized to the extent of 95.7 and 96.1 per cent respectively, which 

 is very close to the values (96.1 and 94.2) which were found on 



