226 FISH HATCHERY MANAGEMENT 



The values above show that salmonids make more efficient use of energy 

 from fats than from proteins, and least efficient use of carbohydrates. There 

 is evidence that trout must use some protein for energy. In trout feeds, 

 between 55 and 65% of the total available dietary calories are from the pro- 

 tein. 



The available calories in 100 grams of a salmon or trout production feed 

 can be calculated as follows: 



Total = 295.5 kcal/100 grams or 1,341 kcal/pound 



An estimated conversion can be calculated for salmonids by using the 

 energy requirement to produce a pound of fish and the available calories in 

 the feed. 



kcal to rear a pound of trout (l,700) , 0-7 r i 



' -. r = 1.27 teed conversion 



Available kcal per pound of feed (1,341) 



ENERGY REQUIREMENTS FOR CATFISH 



Available kilocalories required to produce a pound of catfish vary from 881 

 to 1,075, depending on the feed and size of fish. Growth and feed conver- 

 sions demonstrate that larger catfish require lower levels of protein and 

 higher levels of energy than smaller catfish. Nutrient digestibility and en- 

 ergy values for catfish are: 



