GROWTH 



415 



on calves, those of Weiske J on lambs, and those of Forbes 2 

 and of Weiser 3 on pigs. 



Arranging the available results upon the retention of cal- 

 cium and phosphorus per 1000 live weight in order of the age of 

 the animals, irrespective of the species, gives the following 

 showing of the effect of age upon the rate of gain of these two 

 elements. It appears that in suckling animals, the rate of 

 gain of the ash ingredients, like that of protein and energy 

 (463, 464), is relatively high, while there is a distinct falling 

 off in the rate as the animal grows older, although not to the 

 same extent as in the case of the organic nutrients. 



TABLE 103. DAILY RETENTION PER 1000 LIVE WEIGHT 



The data of the foregoing experiments hardly afford an 

 adequate basis for estimating the ash requirements at different 

 ages. As compared with the amounts of mineral elements con- 

 sumed in or assimilated from the feed, the body, of even a very 

 young animal contains a large stock of these substances which 

 can be drawn upon to a certain extent to meet any temporary 

 deficiency in the feed. It is possible, therefore, that the amounts 

 retained in the relatively short periods of the foregoing experi- 

 ments may be less than are necessary or desirable for continuous 

 normal growth. On the other hand it would appear from 

 Forbes' results 4 that, under favorable conditions, ash may be 

 stored in the bones in excess of the actual maintenance needs 

 and constitute a reserve of mineral matter in the body. The 



1 Landw. Jahrb., 9 (1880), 205. 

 3 Biochem. Ztschr., 44 (1912), 279. 



2 Ohio Expt. Sta., Technical Bui. 5, p. 378. 

 4 Loc. cit., p. 371. 



