66 FEEDS AND FEEDING 



animals which have finished their growth, rations containing plenty of 

 good-quality roughage will usually furnish sufficient mineral matter, 

 except common salt. As shown later, it is in general always advisable 

 to supply farm animals common salt in addition to that in their feed. 

 Since over 90 per ct. 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. As is 

 advised later (916), it is usually wise to keep a supply of a suitable 

 mineral mixture before pigs, at least when confined to pens. 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. 



98. Calcium and phosphorus. When the supply of either calcium or 

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

 house, doling out these minerals so that the life processes of the body 

 may continue normally for a time. Under such conditions the calcium 

 and phosphorus in the muscular tissues and other vital tissues of the 

 body remain practically as high as in animals liberally supplied with 

 these minerals. In a trial at the Wisconsin Station 12 by Hart, McCol- 

 lurn, and Humphrey a cow fed a ration deficient in calcium during 110 

 days gave off 5.5 Ibs. more calcium in milk and excrement than was in 

 the feed. This was about one-fourth of all the calcium in her body, 

 including the skeleton, at the beginning of the trial. 



Such withdrawal of mineral matter from the skeleton produces porosity 

 and brittleness of bone. In certain localities where the hay and other 

 roughages are especially low in calcium and phosphorus, farm animals 

 are so affected by the lack of these mineral substances that their bones 

 are broken easily and in seemingly inexplicable ways. Often this brittle- 

 ness of bone is noticeable only in years when the normal absorption of 

 calcium and phosphorus by the roots of plants is hindered by drought. 

 Of grown animals, those carrying their young are most apt to suffer 

 from the lack of these substances, since considerable amounts are de- 

 posited in the fetus. Growing animals whose bones are rapidly increas- 

 ing in size suffer from a lack of calcium or phosphorus sooner than 

 grown animals. 



Fortunately, roughage from the legumes, such as clover and alfalfa 

 hay, is especially rich in -calcium and is also quite high in phosphorus. 

 Previously the high value of these roughages in stock feeding has been 

 attributed primarily to their richness in protein. Experiments carried 

 on continuously since 1908 at the Wisconsin Station 13 by Hart, Steen- 

 bock, and Humphrey have shown clearly that the beneficial effects of 

 leguminous roughages are also due to their richness in lime. Dry cows 

 fed oat or wheat straw, with grain and grain by-products added to 



"Research Bui. 5; Am. Jour. Physiol., 1909. 



13 Wis. Res. Buls. 17 and 49; Buls. 287 and 323, pp. 15-17. 



