56 BULLETIN 905, U. S. DEPARTMENT OF AGRICULTURE. 
RESULTS OF IOWA EXPERIMENT IN GRADING UP SCRUB DAIRY STOCK. 
The table indicates that a heifer which has developed ' under 
favorable conditions will produce more milk than one which did not 
have this advantage (increase of 27 per cent in milk, 24 per cent in 
butterfat). The most important thing brought out, however, is 
the great improvement made by one cross with purebred sires (38 
per cent in milk production, 32 per cent in butterfat). The data for 
three-quarter bloods are rather meager, but show such a very great 
increase that it can be hardly doubted that a substantial increase 
over the first cross will be shown when larger numbers are available. 
When each of the grade cows is compared with her scrub dam or 
granddam, the improvement appears even more striking, owing to 
the fact that some of the dams were in the group of scrubs which 
were mature when brought to the station. Considerable difference 
was found in the value of the different bulls used. One of them 
produced hardly any improvement in his daughters, while others 
were responsible for a big increase in production. 
It is important to understand the essential difference between a 
good and a poor producer. An investigation by C. H. Eckles, of 
the University of Missouri, brought out no important differences 
in the quantity of feed used by the cows merely in maintaining their 
weight when dry, nor in the amount of milk and butter produced 
by a given amount of additional feed. The good producer merely 
ate more feed in addition to the maintenance ration than the poor 
producer. This does not mean that a better appetite is the cause 
of higher production. The situation is probably the reverse. It 
shows, however, that the greater economy of high producers lies in 
the smaller percentage of their feed used for mere maintenance. 
The average cow, producing 160 pounds of butterfat a year, eats 
about 50 per cent more than if she were dry. H er milk scarcely pays 
for her keep. A cow which eats 100 per cent more than her main- 
tenance requirements should produce twice as much milk as the 
former cow, with only one- third more feed. If the average Ameri- 
can cow were of the latter kind, producing about 320 pounds of 
butterfat in a year, only half as many cows would be needed as at 
present and only two-thirds as much feed would be consumed in 
producing our present milk supply. With still more productive 
cows, milk can be produced still more cheaply, although it should 
be said that the rate of decline in feed cost decreases rapidly for 
production above 320 pounds. As a very considerable number of 
cows, including representatives of all the important breeds, have 
records of 900 pounds of butterfat in a year, the attainment of an 
average of 320 pounds is not a very ambitious undertaking. 
As for the breeds of dairy cows, each has its advantages. The 
Jerseys and Guernseys, for example, produce richer milk than the 
Holstein-Friesians, but en the average less of it. The average- 
