BULLETIN 1144, U. S. DEPARTMENT OE AGRICULTURE. 
It is evident that high-producing cows need more feed than low- 
producing cows. It is conceivable that production may be limited 
by lack of sufficient feeds of the proper kind. How far it is possible 
to increase production by supplying more feed is a question which 
can be answered only by trial, but it was acknowledged by some of 
the farmers reporting that their cows gave, in 1920, less milk than 
usual because of restricted grain feeding owing to relative prices of 
feeds and milk. The higher yields must usually be obtained by 
increased use of concentrates. Cows use digestible protein and net 
energy for two purposes ; first, to maintain their bodies, and, second, 
for producing milk or flesh. The protein and net energy devoted to 
the first purpose are called the maintenance requirements and the 
feed supplying them the " maintenance ration." Whatever digestible 
protein and net energy there may be in the ration above the main- 
tenance requirements are devoted to production. Milk production 
Fig. 1. — Computations of the net energy supplied to cows as reported by farmers com- 
pared with standard requirements show a very intimate relation between quantity 
of feed and quantity of milk produced, a relation which liberal feeders turn to their 
advantage. 
may be limited by the amount of digestible protein supplied, and as 
the annual yield increases more attention must be given to this factor 
(as feeders recognize by adding more grain), especially the high- 
protein concentrates for their best cows. Total amount of feed, even 
of a well-balanced ration, may be a limiting factor in "milk produc- 
tion. The amount of milk produced is the basis for feeding cows 
individually instead of giving the same amount to each. Some 
feeders still persist in the latter practice. 
The relation between the maintenance requirements, total require- 
ments, and milk production at rates up to 13,000 pounds per year is 
indicated in Figure 1. The upright bars show the production per 
cow in nine cases ; H represents the highest herd ; L, the lowest herd ; 
A, B, C, D, and E, the averages of the groups into which the farms 
are divided; K, a single cow reported by Professor Eckles; and P, 
120 cows taken from the Eegister of Production (Circ. 129 of the 
Wisconsin Agricultural Experiment Station). The full length of 
