A STUDY IN THE COST OF PRODUCING MILK. 13 
amount of capital so invested per cow at any one time is compara- 
tively small. Dairy equipment includes such items as separators, 
coolers, wagons, pails, cans, bottles, and other miscellaneous articles 
used in connection with the care of milk and the cows. The annual 
cost for these items includes depreciation, repairs, and interest on the 
average capital invested. The depreciation is the difference between 
the inventory value at the beginning of the year, plus the sum of all 
items purchased, and the inventory value at the end of the year. 
On these four farms this equipment charge, as shown in Table I, 
ranges from $1.28 to $3.22 per cow, which is from 1.3 to 2.5 per cent 
of the total cost of the cow per year. 
USE OF BULL. 
The net cost of keeping a bull is one of the expenses of producing 
milk. This cost includes feed, labor, interest, and depreciation. 
The last two items are in proportion to the value of the bull. Where 
heifers are raised to maintain the herd it has been proved to be poor 
economy to keep a scrub bull, however low the cost. The increased 
value at birth of the heifers sired by a bull of high quality will far 
more than offset the increased charge for use of the better bull. 
The size of the herd is also an important factor affecting the cost per 
cow. The charge for use of bull varies on each of the four farms, 
according to the number of cows and the value of the bull. This 
ranges from $1.47 to $3.52 per cow, the average being $2.44. This 
is from 1.3 to 2.7 per cent of the total cost of keeping a cow. The 
highest charge is in the smallest herd, and the smallest charge is in 
the herd where there is the largest number of cows per bull. 
INTEREST. 
There is a certain amount of money invested in the cows of the 
dairy herd upon which the owner is entitled to receive interest. 
In these records interest is charged at the rate of 5 per cent on the 
average value of the cows for the year. This item ranges from 2 to 4.4 
per cent of the total cost. The high interest charge on the North 
Carolina farm is due to the fact that several pure-bred Holstein heifers 
were purchased during the record period. 
DEPRECIATION. 
Some of the factors influencing depreciation charge are udder 
troubles, failure to breed, abortion, minor accidents, age, and death. 
Usually the loss from death is small compared with the shrinkage 
in value of cows sold at meat prices. The formula used in determin- 
ing depreciation on each of the four herds is: First inventory value 
plus the value of cows entering by purchase or otherwise, minus 
the second inventory value plus the receipts from sales of cows, 
equals the amount of depreciation for any given period. The de- 
