FEEDING STANDARDS AND FEEDING 477 



nearly the same productive value as corn chops, it can replace 

 corn chops without materially altering the productive value of 

 the ration. If one pound average cottonseed meal containing 0.352 

 pounds digestible protein replace one pound corn chops contain- 

 ing 0.065 pounds digestible protein, the digestible protein increases 

 0.352-0.065 = 0.287 pounds, so that to increase the ration 1.14 

 pounds, we require 1.14 divided by 0.287 4.0 pounds cottonseed 

 meal in place of an equal quantity of corn chops. The ration 

 would then consist of 17.9 pounds cottonseed hulls, 7.1 pounds 

 corn chops, and 4 pounds cottonseed meal. The substitution of 

 i pound cottonseed meal for I pound corn chops decreases the 

 productive value 0.206-0.195 = o.oi, or 0.04 pounds for the 4 

 pounds substituted; and this can be adjusted by adding 0.25 

 pounds corn chops, making a total of 7.35 pounds corn chops in 

 the ration. This finally gives the ration desired. 



The method of calculation here given is as follows : 



(1) Assume the bulk desired is composed of the roughage to 

 be used and calculate its productive value. 



(2) Calculate the quantity of concentrate which would give 

 the desired productive value if it replaced a portion of the rough- 

 age. 



(3) Calculate the proteids in the mixture having the composi- 

 tion ascertained above, and then calculate the quantity of a con- 

 centrate, rich in proteids, which must replace a portion of the 

 other concentrate in order to give the desired quantity of pro- 

 teids. The calculation is easier if the two concentrates have 

 nearly the same productive value. 



(4) Adjust the ration by increasing or decreasing the quantity 

 of one of the concentrates slightly, so that the change in the 

 productive value caused by the second concentrate may be 

 allowed for. 



Improving a Ration. Suppose a horse weighing 1,000 pounds 

 at hard work, plowing for example, is receiving 7 pounds corn, 6 

 pounds wheat bran, and 12 pounds timothy hay. How does this 

 ration compare with the standard and how can it be improved? 



