630 3. Die höheren Lebenseinheiten. 



differing: The respiration calorimeter experiments, of course, included deter- 

 minations of the digestibility of the rations and of the nitrogen balances of 

 the animals." 



The chief results of the investigations are (in the author's words) as follows : 



„The respiration calorimeter experiments failed to show that either the 

 type or age of the steers exerted any material infiuence lipon the percentage 

 digestibility of the feeding stuffs or upon the proportion of their energy which 

 was metabolized. As regards the portion of their energy which was available 

 either for maintenance or for production, slight differences were observed in 

 favor of the purebred steer and, in case of the grain, of the older as com- 

 pared with the younger animal, but it is questionable whether they were large 

 enough to be of practical significance." 



„On the limited grain ration of the periods outside the respiration calori- 

 meter experiments, the scrub steer consumed relatively more hay than did the 

 purebred animal, made an equal gain in live weight per head, and a materially 

 greater one per unit of weight, and consumed somewhat less total air-dry feed 

 per unit of grain." 



„This apparent discrepancy between the results of the respiration calori- 

 meter experiments and those of the remainder of the investigation appears to 

 have been due chiefly to a difference in the composition of the increase in 

 live weight in the two animals. The nitrogen balances show a notably 

 greater tendency toward a storage of protein by the scrub than by the pure- 

 bred steer, while the respiration-calorimeter experiments, on the other Land, 

 show a materially greater gain of fat by the latter than by the former. In 

 other words, the gain in weight by the scrub as compared with that by the 

 purebred steer consisted more largely of protein with its accompanying water 

 and to a smaller extent of fat, and therefore represented a materially smaller 

 storage of feed energy. A similar conclusion was indicated by the results of 

 the block test. From the data obtained for the available energy of the ra- 

 tions it is estimated that a kilogram of gain in live weight by the purebred 

 steer was equivalent on the average to the storage of 40 percent more energy 

 than in the case of the scrub." 



„The energy requirement of the scrub steer for maintenance, computed 

 to the same live weight, averaged 18,7 per cent higher than that of the pure- 

 bred steer. Accordingly, the latter was able to use a relatively larger pro- 

 portion of the total energy of his ration for the production of gain. A distinct 

 infiuence of age upon the maintenance requirement was observed between the 

 ages of 14 and 39 months, the requirement decreasing relatively as the ani- 

 mals matured." 



„In those of the respiration calorimeter experiments in which a heavy 

 grain ration was fed, it was found that the purebred steer had a notably 

 greater feeding capacity than the scrub steer — that is, he could be fed 

 larger rations of grain, which he utilized to the same degree as did the scrub." 



While, tlien, our results fail to show any material differences between 

 the physiological processes of food utilization in the two animals, they also 

 show clearly an economic superiority of the purebred over the scrub steer, 

 due, first, to his relatively smaller maintenance requirement, and, second, to 

 his ability to consume a larger surplus of feed above that requirement. Both 

 these factors tend to make the actual production of human food in the form 

 of meat and fat per unit of total feed consumed by the animal notably greater 

 by the purebred animal. In these experiments this difference was masked by 

 the inferior quality of the increase made by the scrub steer, so that on the 

 basis of live weight alone the latter appears superior to the purebred animal." 



