38 PRINCIPLES OF FEEDING FARM ANIMALS 
mann standards become very simple and are as easily applied as any 
standard so far proposed for farm animals. 
The nutritive ratio of a feed (or a ration) is the proportion 
between the digestible protein and the sum of the digestible carbo- 
hydrates and fat contained therein. The fat is changed to its 
carbohydrate equivalent by multiplying with 2.25, because it has 
2.25 times as high heat value as similar amounts of carbohydrates. 
For example, the nutritive ratio is expressed as 1: 6.5, meaning that 
there are 6.5 pounds digestible carbohydrates and fat combined 
for every pound of digestible: protein. The nutritive ratio is cal- 
culated as follows, e.g., in the case of the first ratio given above: 
0.5 (digestible fat) 2.25 = 1.13; 
15.0 (digestible carbohydrates) +- 1. 13 (the carbohydrate equiv- 
alent of the digestible fat) = 16.13; 
16.13 + 2.5 (digestible protein) = = 6.5. 
The nutritive ratio of the ration for milch cows given is figured 
in the same way, as follows: 
5 XK 2.25 = 1.18; 
13.0 41.13 = 14.13; 
14.13 + 2.5 = 5.7; the nutritive ratio is, therefore, 1 : 5.". 
The Armsby Standards. —The estimated feed requirements for 
different classes of farm animals according to Armsby are given in 
the following table; the figures show the amounts of digestible true 
protein and energy values, expressed in therms, that should be sup- 
plied daily to growing cattle and sheep at different ages. These 
figures in all cases include the maintenance requirements for the 
various animals.® 
Estimated Feed sas per Day and per Head (including the Maintenance 
Requirements).—Armsby. 
Growing cattle Growing sheep 
gers Live Digestible Energy Live Digestible Energy 
weight, protein, values, weight, protein, values, 
- pounds pounds therms pounds pounds therms 
3 275 1.10 5.0 ine or 
6 425 1.30 6.0 70 30 1.30 
9 I ted gab pe 90 25 1.40 
12 650 1.65 7.0 110 23 1.40 
15 ae ae a 130 23 1.50 
18 850 1.70 7.5 145 22 1.60 
24 1000 1.75 8.0 isnt i 
30 1100 1.65 8.0 St 
5 Farmers’ Bulletin 346. 
