308 FEEDING VALUES MANUKIAL VALUES 



as the values of digestible carbohydrates, fats and protein, the latter 

 including both albuminoids and amides, the error introduced by in- 

 cluding the latter as protein being counterbalanced by the fact that the 

 manurial value of the undigested nitrogenous matter has been ignored. 



He further estimates the value of digestible carbohydrates at 1-24 

 shilling "per unit" per ton, or say, practically, Is. 3d. " per unit" 

 per ton. 



The values of the three chief ingredients of feeding stuffs thus 

 become 



By adding the percentages of digestible fat and digestible protein 

 together, multiplying their sum by 2*5, and adding the percentage of 

 digestible carbohydrates, the number of "food units" in the food is 

 obtained. 



To calculate the value per ton, it is then only necessary to multiply 

 the food units by Is. 3d. 



It will be found, in practice, that if it be assumed that the total 

 carbohydrates be worth Is. per unit and the total fat and albuminoids 

 2s. 6d. per unit, the value, calculated per ton on this basis, will be 

 roughly correct. 



It is obvious that accuracy is not possible in such calculations and 

 that the values are liable to great fluctuations. 



. The Manurial Value of Foods. When food is supplied to an 

 adult animal which is not increasing in weight nor producing milk or 

 wool, the whole of the manurial constituents of the food will be re- 

 covered in the excreta, and, if subsequent loss by fermentation or drain- 

 age be prevented, may be restored to the land. 



It is otherwise with growing, fattening, or milk-producing animals. 

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

 nitrogen, phosphoric acid and potash is employed in forming the in- 

 crease, 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 per cent 

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

 the whole. 



According to Lawes and Gilbert, 1 the proportion of the total 

 nitrogen of the food, retained in the fattening increase of oxen and 

 sheep, varies from about 3 per cent with decorticated cotton cake (con- 

 taining 6-6 per cent of total nitrogen) to as high as 14 per cent with 



1 Jour. Eoy. Agric. Soc., 1885, 600. 



