306 NUTRITION OF FARM ANIMALS 



merits on dogs by Kleinert 1 and by Schlossmann and Mursch- 

 hauser 2 seem to point in the same direction. 



Observations made by Zuntz and Hagemann 3 on the horse 

 appear suggestive in this connection. In a series of respiration 

 experiments they have confirmed the common observation that 

 a surplus of feed above the maintenance requirement stimu- 

 lates the muscular activity and restlessness of this animal, so 

 that a ration may be considerably more than sufficient to main- 

 tain the animal when standing quietly in the stall and yet 

 give rise to no increase in weight under ordinary conditions. 

 A similar stimulating effect of the feed upon the minor muscular 

 movements of cattle, expecially while standing, seems to be in- 

 dicated by the experiments of Armsby and Fries (367 e). It 

 seems possible that part, at least, of the diminution of the main- 

 tenance requirement observed by Waters may have been due 

 to a voluntary restriction of motion on the part of the animals 

 on the low nutritive plane. 



In attempting to determine experimentally the minimum 

 maintenance requirement it is evidently the safer method of 

 procedure, especially with the horse, to approach the main- 

 tenance point by gradually increasing a sub-maintenance ration, 

 as in Miintz's experiments on the horse (386 c) and those of 

 Armsby and Fries on cattle (374) rather than by the gradual 

 reduction of a supermaintenance ration. 



393. Fattening. That fat animals have a relatively greater 

 maintenance requirement than thin ones seems to be fairly 

 well established for cattle by the experiments of Kellner and 

 of Evvard, the results of which are recorded in Table 48 (381). 



One obvious reason why the maintenance requirement per 

 head should be greater for a fattened animal than for the same 

 animal before fattening is the greater muscular effort expended 

 in standing, due to the greater weight to be supported. Zuntz 

 and Hagemann, in experiments upon the horse carrying weight 

 on its back, found that this increase was proportional to the 

 amount of weight added (665). If this be true generally, then 

 that portion of the metabolism due to standing will increase 

 more rapidly than the body surface. In Armsby and Fries' 

 experiments on unfatted cattle, however, the energy expendi- 



1 Ztschr. Biol., 61 (1913), 346. s Biochem. Ztschr., 53 (1913), 265. 



3 Landw. Jahrb. 27 (1898), Ergzbd. Ill, 211, 236. 



