76 ILLINOIS STATE DAIRYMEN'S ASSOCIATION 



ant injury to the animal. For instance, magnesium and cal- 

 cium seem antagonistic in their action, and in voiding the 

 excess of magnesium the body loses calcium. Given in ex- 

 cessive amount for long periods, feeds which contain much 

 magnesium in proportion to calcium, such as wheat bran 

 and middlings, are said to cause a weakening of the bones, 

 leading to such troubles as "bran disease" or "miller's 

 horse rickets. ,, This does not mean that bran or middlings 

 are not among our most valuable and healthful feeds when 

 properly fed in combination with other feeds. 



Mineral Requirements for Maintenance. 



The common feeding stuffs contain all the necessary 

 mineral salts, at least in small amounts. As a rule, the 

 roughages, except some of the straws, are much richer than 

 the grains in mineral matter. Moreover, the body is prob- 

 ably able to use many of the mineral compounds over and 

 over, taking them back again into the circulation after hav- 

 ing been used. Therefore, for animals which have finished 

 their growth, rations containing plenty of good-quality 

 roughage will usually furnish sufficient mineral matter, ex- 

 cept common salt. It is in general always advisable to sup- 

 ply farm animals common salt in addition to that in their 

 feed. 



Since over 90 per cent of the mineral matter of the 

 skeleton consists of calcium (lime) and phosphorus, these 

 mineral constituents may also fall short in some rations, 

 especially in those for young, growing animals, which need 

 an abundance for building their skeletons, and for dairy 

 cows, which need an abundance of calcium and phosphorus 

 for their milk. As is shown later, under certain conditions 

 . there may be a lack of iodine in the feed, which may cause 

 serious results. The special requirements for these mineral 

 constituents are discussed in the following paragraphs. 



Calcium and Phosphorus. 



When the supply of either calcium or phosphorus is 

 too low in the feed, the skeleton acts as a reserve store- 



