302 FOODS AND FEEDING. XIII. 



In such cases a portion, and sometimes a considerable portion, 

 of the nitrogen, phosphoric acid, and potash is employed in 

 forming the increase, and only the residue remains in the 

 excreta for use as manure. 



The proportion of the total nitrogen of the food retained by 

 an animal varies greatly, not only with the individual, but also 

 with the composition of the food. 



A young calf fed on milk will retain as much as 69 or 70 % 

 of the nitrogen in its food, while a horse will, if full grown, 

 excrete the whole. 



According to Lawes and Gilbert,"- the proportion of the total 

 nitrogen of the food retained in the fattening increase of oxen 

 and sheep varies from about 3 % with decorticated cotton cake 

 (containing 6'6% of total nitrogen) to as high as 14% with oat 

 straw (containing only 0'5% of total nitrogen). With many 

 foods it averages about 5 or 6 % of the total nitrogen in the 

 food. With phosphoric acid the same investigators found that 

 from 3 or 4% (with bran, malt coombs, Ac.) to 19 or 20% (with 

 maize, rice meal, barley straw, oat straw, &c.) of the total 

 present in the food was retained by fattening oxen and sheep. 

 With potash the corresponding figures were 0'3 or 0'4% (with 

 roots) to 3 or 4% (with malt, maize, &c.). 



The Eothamsted experiments, as summarised by Waring- 

 tonf, yielded the following results : 



Percentage of nitrogen obtained as increase or 



voided in manure. 



% in carcass 0/ . . % in total 



or milk. excrements. 



Horse working ... O'O 70*6 100-0 



Fattening ox ... 3'9 73-5 96-1 



sheep ... 4-3 79-0 95-7 



pig ... 14-7 60-3 85-3 



Milch cow ... 24-5 57-4 75-5 



Calf fed on milk . 69'3 25'6 30-7 



With the ash constituents the following were the results : 



For 100 consumed as food. 

 In live-weight increase Voided a,s manure 



or milk. or in perspiration. 



Horse ... 0-0 100-0 

 Fattening ox ... 2-3 97'7 



* J.R.A.S. 1885, 600. t Chemistry of the Farm, 162. 



