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lai.I.KTIX 1144, U. S. DEPAETMKNT OF AC, UHTLTURE. 



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 Register of Production (Circ. 129 of the 

 Wisconsin Agricultural Experiment Station). The full length of 



