4 BULLETIN 858, U. S. DEPAKTMEXT OF AGRICULTURE. 
"net cost of production'* are used, these terms do not include the 
charge for managerial ability. If it is desired to include managerial 
ability as a cost of production, when determined by any method 
selected, this amount may be added to the cost of production. 
INFLUENCE OF SEASONS ON COST FACTORS. 
Since the winter and summer seasons have a marked influence on 
the principal factors entering into the cost of producing milk, the 
results have been computed separately for those periods. The 
months from November to April, inclusive, represent the winter 
season, and from May to October the summer season. This division 
Fig. 1.— Better breeding saved labor. The owner of this herd of cows, averaging 9.200 pounds of 
milk annually, had to feed and milk only 9 cows to obtain as much milk as 12 average association ~ 
cows produced. 
of time was based directly on the change hi methods of herd manage- 
ment made hi November and May. 
The various tables hi this bulletin are based upon figures ob- 
tained during the 2 years of the study, and all results are expressed 
hi weighted averages in which the weights represent the relative 
importance of the separate items averaged. 
DESCRIPTION OF HERDS. 
During the first year the 16 herds on which records were tabulated 
contained 334 grade and purebred cows, mostly of the Holstein 
breed, which produced on the average 6,877 pounds of milk testing 
3.8 per cent butterfat. In the 21 herds included hi the study the 
second year there were 404 cows of approximately the same breeding 
