NUTRITION AND FEEDING 245 



The proper use of this method helps assure optimum feeding levels. It 

 determines the feeding level regardless of the caloric content of the feed, 

 because this is considered in the feed conversion. 



When the water temperature, diet, and species remain constant, all 

 numerator factors in the feeding formula remain constant. Multiplication of 

 the numerator factors establishes a Hatchery Constant (HC): 



HC = 3x conversion x AI x 100. 



The percent of body weight to feed daily for any length of fish can be ob- 

 tained by dividing the Hatchery Constant by the length of fish {L) in 

 inches. 



FfC 

 Percent of body weight feed daily = 



The Hatchery Constant {HC) is used in the following example to calculate 

 feed requirements. We must calculate the amount of feed required on April 

 10th for 20,000 fish averaging 100 pounds per 1,000 fish or 6.3 inches on 

 April 1st. The expected growth during April is 0.60 inches and the feed 

 conversion is 1.2 pounds of feed per pound of growth. 



Length increase per day (AZ-) = 0.60 inches 



Length, April 1st = 6.30 inches (lOO pounds/1,000 fish) 



Growth, 10 days X 0.020 = 0.20 



Length, April 10th = 6.50 inches (llO pounds/1,000 fish) 



20,000 fish X 110 pounds/1,000 = 2,200 pounds offish April 10th 



//C= 3 X 1.2X0.020 X 100 =7.2 



HC 7 2 



Percent body weight to feed = = — ' — = 1.1% (O.Oll) 



L 6.50 



2,200 pounds fish x 0.011 = 24.2 pounds of feed required on 



April 10th for the 20,000 fish. 



The above method of calculating feed can be used to project the amount 

 of feed required for a raceway or pond for any period of time. Many sta- 

 tions use this method to set up feeding programs for the coming month. 



