THE MAINTENANCE REQUIREMENT OF DRY COWS 1 
By Donald C. Cochrane, Associate in Animal Nutrition, J. August Fries, 
Assistant Director, and Winfred W. Braman, Associate in Animal Nutrition, 
Institute of Animal Nutrition, Pennsylvania State College 2 
INTRODUCTION 
The determination of the maintenance requirements of farm ani¬ 
mals is one of the most important of the basic problems of animal 
industry. The maintenance requirement is the nutriment necessary 
for sustenance alone, under the living conditions of production. It 
is therefore the basic requirement to which must be added the direct 
cost in nutriment of the material product or the labor sought. It 
Is a permanent “ overhead” the extent of which must be known 
before total requirements and costs of production can be satisfactorily 
determined. 
Several methods have been used in the determination of mainte¬ 
nance requirements. Two of these, at least, are of such nature as to 
yield data of scientific significance. 
With man and with carnivora the determination of the body 
losses during complete fast have yielded relatively accurate measures 
of the nutriment required to repair tissue waste and to supply the 
energy needed to keep the body machinery running. With herbiv- 
ora the problem becomes much more complex, because with these 
animals the capacity and the anatomy of the digestive tract are such 
as to render difficult and uncertain the attainment of complete and 
actual post-resorptive fast. 
Fortunately there is another angle of approach to this problem, 
namely, that proposed by Rubner in his work on isodynamic re¬ 
placement, and amplified by Armsby (#) 3 for the purpose of deter¬ 
mining maintenance requirements. This method compares the 
effects produced by different amounts of feed, such effects being 
considered as constituting a linear function of the amount of the 
feed. The essential correctness of this postulate, within certain 
limits, has been established by the classic experiments of both Rubner 
and Armsby. 
As an illustration of the method the writers quote from Armsby 
(#, V • 34) : 
The addition of 2.1 kilograms of timothy hay, equivalent to 3.575 therms of 
metabolizable energy, to the basal ration reduced the loss of energy from the 
1 Received for publication Apr. 30, 1925; issued January, 1926. 
2 The experiments on which this paper is based were planned by H. P. Armsby. Responsibility for 
execution of the details rested largely with J. A. Fries. The computations were made, in large part, by 
W. W. Braman. The writers wish to express their appreciation of the assistance of E. B. Forbes, director 
of the institute, in the preparation of the data. They are especially indebted to Max Kriss for his assistance 
in making the intricate computations and handling the animals during the experiments. They also ac¬ 
knowledge the efficient work of C. D. Jeffries, W. J. Sweeney, R. M. Meredith, Raymond Peterson, and 
others, who at various times gave their services for the success of the involved and exacting experiments. 
3 Reference is made by number (italic) to “ Literature cited,” p. 1081. 
Journal of Agricultural Research, 
Washington, D. C. 
( 1055 ) 
Vol. XXXI, No. 11 
Dec. 1, 1925 
Key No. Pa.-17 
