MAINTENANCE RATIONS OF CATTLE. 



41 



Omitting the results of the year 1904, which are obviously too high both as 

 regards the maintenance requirement and the percentage availability, we ob- 

 tain the following averages in round numbers : 





Available 



Metaboliz- 

 able 





energy. 



energy. 





Therms. 



Therms. 



Per 500 kilograms live weight 



6. 52 



11.63 



Per 1,000 pounds live weight 



G.ll 



10.90 



The variations from these averages which occur in individual cases illus- 

 trate the fact, already pointed out, that the economic as distinguished from 

 the physiological requirement may vary considerably with different animals 

 and under different conditions. 



The experiments just cited are the only ones thus far reported in 

 which this precise method of determining the maintenance require- 

 ment in terms of available energy has been followed. In the major- 

 ity of investigations the effort has been to feed as nearly an exact 

 maintenance ration as possible, making a correction for the small 

 gains or losses by the animals, and the results of these experiments 

 have usually been expressed in terms of metabolizable energy. 



By far the most exact and satisfactory experiments of this sort, as well as 

 the earliest, are those reported by Kellner from the Moeckern Experiment 

 Station 1 in 1894 and 1896, in which the gain or loss of protein and fat (nitro- 

 gen and carbon balances) was determined by means of a Pettenkofer respira- 

 tion apparatus. In these experiments the feed consisted exclusively of coarse 

 fodder, viz, meadow hay, or, in two instances, a mixture of clover hay and 

 oat straw. In six cases out of the eight the respiration experiments showed a 

 small gain of protein and fat by the animal ; that is, the ration was somewhat 

 above the maintenance requirement. For example, the gains by ox A on meadow 

 hay and the computed equivalent amounts of energy were : 





Material 

 gained. 



Equivalent 

 energy. 



Protein 



Grams. 

 37.2 

 140.8 



Therms. 

 0. 211 

 1.338 



1.549 



Fat 



Total 







In later investigations by Kellner, out of 100 units of metabolizable energy 

 of meadow hay supplied in excess of the maintenance requirement, only 43 

 were recovered in the protein and fat gained by the body. To produce the gain 

 observed in this experiment, therefore, may be computed to have required 

 1.549-K).43 =3.602 therms of metabolizable energy and the ration must have con- 

 tained this amount in excess of the maintenance ration. The following calcu- 



1 Die Landwirtschaftlichen Versuchs-Stationen, vol. 44, p. 370; vol. 47, p. 310; vol. 53, 

 pp. 6-16. 



