THE COMPOSITION OF FEEDS 193 



ysis is only a rough measure of value. It shows what is in a 

 given feed, but feeds having the same analysis are not necessarily 

 of equal value because the animal body makes better use of the 

 nutrients of some feeds than of others. The big difference lies 

 in the extent to which a feed is digested. Finally, in comparing 

 the general usefulness of feeds we should consider their manurial 

 value. 



322. The manurial value of feeds. — It has been stated that 

 the part of the feed which is excreted in the feces represents the 

 indigestible portion from which the animal gets no value. How- 

 ever, this portion is very useful as fertilizer as we all know. This 

 is such an important item, if the manure is properly handled so that 

 its fertilizing value is not lost, that it should be taken account of 

 in considering the value of feed. 



323. Manure the cheapest fertilizer. — Every crop which is 

 grown takes nutrients out of the soil and the land becomes poorer 

 and less productive each year unless these nutrients are returned 

 either as manure or commercial fertilizer. Of course the use of 

 manure Is much the cheaper method. Here the dairyman has a 

 great advantage over the hay and grain farmer because he has a 

 lot of manure to use, coming from both feeds he raises and feeds 

 he purchases. In order to make the most of this advantage he 

 must know the feeds from which he can get the most fertility. 



324. Conserve the urine. — The fertilizing constituents we are 

 interested in are nitrogen, phosphoric acid and potash. Of course, 

 we must include the urine as well as the solid excreta under the 

 term manure. The urine contains on the average 40 per cent of the 

 nitrogen and 60 per cent of the potash of the total fertilizing con- 

 stituents excreted. This shows how important it is to see that the 

 urine is not lost. Of the total fertilizing constituents in a given 

 feed the amount of each actually excreted in the manure will 

 depend on the animal. Unless an animal is growing or storing fat 

 or making some product such as milk, nearly all of these consti- 

 tuents eventually appear in the feces and urine. A horse which is 

 not gaining in weight, developing a foetus, or nursing a colt must 

 thus return as manure nearly all of the fertilizing constituents of 



