44 DOMESTICATED ANIMALS AND PLANTS 
commercial herds of the state, this difference is exceedingly sig- 
nificant. Rose was, of course, an exceptional cow, producing in 
another test over two and one-half times as much as her com- 
petitor, and making a twelve-year record of 7258 pounds of 
milk, and 360 pounds of butter fat on the average (384 pounds 
of fat for ten years), and never being beaten but once in all the 
dairy tests ever conducted at this station. Professor Mumford, 
also of the University of Illinois, has shown that substantially 
the same differences exist between beef animals in respect to 
the amount of gain for food consumed,! so that the principle 
involved seems general. 
Economic significance of differences in efficiency. The mean- 
ing of all this is not at once clear, and some little effort is 
needed to fully appreciate the economic significance of differ- 
ences such as are here brought out, and the consequent desira- 
bility of bringing our common animals to the highest possible 
degree of efficiency. When one cow can make two and one- 
half times as much as another on the same feed, the difference 
is not as two and one-half is to one, but many times greater. 
Under these conditions, when one cow makes 100 pounds of 
butter, the other will make 250 pounds on the same feed; but 
the question of relative profits depends also upon two other 
factors, —the cost of feed and the price of butter. For the sake 
of illustration let us suppose, first, that it costs the value of 
50 pounds of butter to pay for the food consumed, which is the 
same in both cases. The profit would then be, in the one case, 
the value of 100— 50 (or 50) pounds of butter; and in the 
other, 250 — 50 (or 200) pounds, which is wot two and one-half 
but four times as much. 
Suppose again that feed is higher or butter lower, so that it 
now costs the value not of 50 pounds but of 90 pounds to pay 
for the cost of feed. In this case the profit for the poorest cow 
is the value of 100 — 90 (or 10) pounds of butter, and for the 
other it is the value of 250—g0 (or 160) pounds of butter, 
1 See “Principles of Breeding,” p. 82. 
