Purchased Food, and of its Residue as Manure. 
217 
whether, in addition to a liberal supply of their ordinary bulky 
food, such as straw and turnips, a ton of linseed-cake, or a ton 
of decorticated, or of undecorticated, cotton-cake, or a ton of 
corn, be given to fattening oxen or sheep ; but the value of the 
manure resulting from the consumption of a ton of each of these 
foods will show great differences. 
■The manurial value of food depends mainly on the amount 
of, 1st, nitrogenous matter, 2nd, potash, and 3rd, phosphoric 
acid which passes through the body into the dung of the animals. 
Practically speaking, the whole of the potash and phosphoric 
acid contained in the purchased food pass into the dung of 
fattening-stock. The loss in nitrogen which the food sustains 
passing through the animal has been variously stated by different 
experimenters. By some it is estimated at one-tenth, by others 
at one-sixteenth part of the total amount of the nitrogen in the 
food ; the former estimate probably is the more accurate. On 
the whole, no great mistake will be made if it be assumed 
that 90 per cent, of the total amount of nitrogen of such con- 
centrated food as oilcake, when given to fattening-stock, is re- 
covered in the solid and liquid excrements, presuming that these 
can be collected without loss. 
In the case of young stock or milking-cows not over well 
supplied with concentrated purchased foods, the dung will not 
be quite so valuable as that of fattening-stock, inasmuch as a 
small proportion of the nitrogenous and phosphatic food-con- 
stituents will be stored up during the increase in the live-weight 
of the young animal, or will be expended in the production of 
milk ; still, even in the case of growing store-cattle or milking- 
cows, by far the larger proportion of the nitrogen and the 
phosphates of the food will be rejected in the solid and liquid 
excrements. 
It is well to bear in mind that the estimated -manure-value of 
purchased foods has nothing to do with mere speculation, but 
rests upon well-ascertained facts, brought to light by numerous 
feeding experiments in this and other countries. The rate of 
valuation that may be adopted by different persons may vary ; 
but the statements that the food of fattening-stock, in passing 
through the animal, loses little (if any) of its nitrogen by exhala- 
tion, and none of its mineral constituents, and that, practically 
speaking, the whole of the mineral matter and about nine-tenths 
of the nitrogen of the food are recovered in the dung and urine 
of the animal, are based on carefully ascertained facts. In this 
country, a long series of most carefully conducted and intelligently 
conceived feeding experiments have been made by Mr. Lawes, 
of Rothamsted. These experiments extended over several years, 
