ANIMAL PRODUCTION. 469 



protein, and the availability of the total energy, in both hay and grain, there 

 was no evidence of the possession of any higher digestive power by the pure- 

 bred animal over that of the scrub. 



In a comparison made in 1905 of 2 periods in which different amounts of 

 timothy hay were given 60.51 per cent in the case of the pure-bred steer and 

 55.21 per cent in the case of the scrub steer of the additional metabolizable 

 energy supplied in the larger ration was substituted for the energy previously 

 derived from the katabolism of the body substance, the remainder being dis- 

 posed of by an inci'ease in the heat production of the steer. The results of 

 1906 and 1907 as a whole also seemed to indicate a small but a distinct supe- 

 riority of the pure bred over the scrub steer as regards the availability of the 

 metabolizable energy of the feed. Tlie difference appeared to be more marlied 

 in the earlier years, as the scrub nearly or quite overtook the pure-bred steer 

 in this respect as they reached maturity. 



The growth of the pure-bred steer was more largely in body girth, while the 

 scrub steer increased relatively more rapidly in length and height, or, in other 

 words, the pure-bred steer showed a tendency to fatten, while the scrub inclined 

 to gain relatively more nitrogenous material. " The difference in availability 

 may conceivably be related to the apparent difference in the nature of the gains 

 or losses. 



" As regards any influence of age upon the percentage availability of the feed, 

 the results appear indecisive. In the case of the hay (aside from the question- 

 able results of 1906), the differences are very small and in opposite directions 

 with the two animals. In the case of the mixed grain of 1906 and 1907. there 

 is apparently a tendency to a somewhat greater availability by the older ani- 

 mals. On the whole, the results as regards the influence of age afford little 

 support to the belief in a greater ability of young animals to utilize the metabo- 

 lizable energy of their feed." 



" The experiments of 1907, the results of which were the most satisfactory, 

 show a marked difference between the two animals as regards the maintenance 

 requirement, that of the scrub steer being 33.7 per cent higher than that of the 

 pure-bred steer. The results obtained in 1905 and 1906 ha^e less weight, but 

 nevertheless they show a difference in the same general direction. On the 

 average of the 3 years' experiments the available energy required for main- 

 tenance per 500 kg. live weight was: Pure-bred steer 5,971 calories, scrub steer 

 7,090 calories." 



It is thought that the difference in temperament explained in large part the 

 economic superiority of the beef type. From October 1, 1904, to December 4, 

 1906, the pure-bred steer made an average daily gain of 0.426 kg. and required 

 13.68 kg. of air-dry matter for each kilogram of gain. During the same period 

 the scrub steer made an average daily gain of 0.422 kg. and required 13.37 kg. 

 of air-dry matter in the feed eaten to produce a kilogram of gain, so that the 

 scrub steer produced a unit of gain in live weight upon somewhat less total 

 feed than did the pure-bred steer. The pure-bred steer was superior to the 

 scrub, however, as regards the energy content of the unit of gain. 



" That a unit of gain by the pure-bred steer represented the storage of more 

 energj' than an equal gain by the scrub steer appears to be due largely to the 

 greater proportion of protein with its large amount of accompanying water 

 which seems to have characterized the gain made by the latter. Both the 

 composition of the gain observed in the respiration calorimeter experiments 

 and the results of the nitrogen balance trials show that the scrub steer had a 

 notably greater tendency than the pure-bred steer to gain protein, while the 

 pure bred, on the other hand, was Inclined to store up more fat. This result 



