fj.Sr^ REPORT OF OFFICE OF EXPERIMENT STATIONS. 



I'XjH'riniciits wcri' ciiriiiHl on with :i slvvv to study tlic :i\ ;iil:il)li' ciHTi^y 

 of timothy hay." On the basis of thcorclical coiisicUM-iitions the 

 iiuthors cjiiiic to tlu> coMclusioii that for call If a iiiaintciiaiK-c ration 

 is a (|uostioii of tissue icplactMnciit rath(M' than of hctit production, and, 

 thcroforo, that the value of a *^iven fcedinjr stuff for maintenance 

 depends upon the a\ aihihility of its energy. For instance, it is at least 

 very probahh' that the work of dij»-estion and assimihition in the case 

 of a material like corn meal would he matei-ially less than in the case 

 of hay; or. in other words, that a larger pcrcentaj^e of the enerj^y of 

 the ^Viun would he available for the maintenance of tissue. It would 

 follow from this that in (iase of a ration consisting largely of grain, a 

 less amount of material or of metal)()lizable energy would be required 

 for maintenance than in the case of a ration consisting exclusively of 

 coarse fodder. In other words, the niaintenance ration is a variable 

 rathei' than a constant, depending upon the kind of food used. In the 

 experiments reported the maintenance requirement of the steer, as com- 

 puted, was 10,710 calories, the average weight of the animal during 

 the experiment ))eing approximately 410 kilograms. On the assump- 

 tion that the maintenance re(]uirement is proportional to the two-thirds 

 power of the live weight, this equals 12,197 calories per 500 kilogiams 

 live weight. 



An important feature of the experiments is the information they 

 afford regarding the substituting value of nutrients. This and other 

 theoretical questions connected with the metabolism of matter and 

 energy are discussed at length. 



aU. S. Dept. Agr., Bureau of Animal Industry Bui. 51. 



