THE COMPOSITION OF FEEDS 191 



The process of fattening consists of building up this reserve by- 

 continuous feeding of energy-forming material in excess of the 

 animal's requirements for it. Since fat is one of the principal 

 constituents of milk, the production of the latter requires a liberal 

 amount of fat-forming material in the feed. 



318. Protein important. — Of the nutrients mentioned, pro- 

 tein is the dominant one, because no other nutrient can serve as a 

 substitute for it, either for growth or milk production. The case is 

 different as regards carbohydrates and fats in that, although the 

 body must have energy to carry on its processes, either of these 

 two nutrients can supply it. If both are insufficient, protein itself 

 can be used as energy. Similarly, carbohydrates and fats can be 

 used interchangeably for the manufacture of these nutrients in 

 milk and for the production of fatty tissue, or even protein may be 

 employed for these purposes by means of certain chemical changes 

 in the body. Thus we have become accustomed to state that the 

 body requires a certain amount of protein plus sufficient total 

 nutrients to supply the needed energy, with the understanding 

 that fats, carbohydrates and proteins may all serve to furnish this 

 energy. 



319. Mineral elements.— This group of nutrients, collectively 

 referred to as ash, comprise two to four per cent of the animal body. 

 There are many different mineral elements but only two, aside 

 from common salt, require consideration in putting together 

 rations. 



320. Phosphorus and lime. — The phosphorus of plants 

 occurs principally in the seeds where it is located in the germ or 

 branny coating. It does not occur in any considerable amount in 

 hulls or stems. The leaves have more than the stems but less than 

 the seeds. 



Lime, on the other hand, occurs in largest amounts in the 

 leaves, to a lesser extent in the stems, and only in small amounts 

 in the seeds. Thus, the chief source of this mineral is the roughage, 

 and leafy roughage is far superior to the other kind. The farmer 

 who feeds plenty of alfalfa or clover and a grain mixture made up 

 of high grade feeds has the ration which is best from the standpoint 



