440 NUTRITION OF FARM ANIMALS 



of the gain during the later stages of feeding as had been generally 

 found by other experimenters. 



There is no sufficient evidence on record to show whether or 

 not the actual percentage utilization of the excess feed dimin- 

 ishes with the advance of fattening. 



Breed and Individuality 



That both those inherited qualities which characterize the 

 recognized meat breeds and the individual differences between 

 single animals are important factors in the economy of meat 

 production is generally recognized. It is a fact of common 

 observation that marked differences exist between individual 

 animals as regards the return which they yield for the feed con- 

 sumed, but the reasons for these differences have not always been 

 clearly seen, and in particular there has been a tendency to 

 assign them to physiological causes, such as difference in di- 

 gestive or assimilative power, and some unwarranted con- 

 clusions on these points have gained currency. 



615. Digestive power. The superiority of one breed or 

 animal over another as regards feeding capacity is often as- 

 cribed to a difference in the extent to which the feed is digested, 

 although those who make this assertion often understand by 

 digestion what is more properly termed " utilization." Un- 

 doubtedly there are differences in digestive power between 

 different animals, but except in the case of manifestly ab- 

 normal animals they have been found to be comparatively 

 slight and 'quite insufficient to account for the marked differ- 

 ences in production (718, 719). Neither is there any evidence 

 that the improved breeds of meat-producing animals possess 

 any superiority in this respect over the ordinary unimproved 

 animals. 



An illustration of the latter fact is afforded in experiments by 

 Armsby and Fries, 1 in which no material difference was observed in 

 the digestive powers of a pure-bred beef animal and a " scrub" at 

 the approximate ages of one, two and three years. The same experi- 

 ments also failed to show any material differences in the losses of 

 energy in urine and methane, so that the percentage of the feed 

 energy which was metabolizable, especially when computed on the 



1 U. S. Dept. of Agr., Bur. Anim. Indus., Bui. 128 (1911). 



