SCIENTTFK^ SWINE FEEDING 235 



tenance. The animal body uses material not only while it is 

 tioing actual work- — putting on gains in live weight or doing 

 labor of various kinds, but for maintenance at all times. 



This being true, it emphasizes the fact that the quicker a 

 pig can be brought up to a desirable market weight, other 

 things being equal, the less feed will be used for maintenance 

 and the more economical will be the gains made. Further- 

 more, as an animal gets older it gradually loses its power to 

 eat and digest large quantities of feed, consequently the factor 

 of maintenance becomes a gradually more important factor as 

 the animal grows. 



MINERAL MATTER 



A pig must have a certain amount of mineral matter, wood 

 ashes, for example. In an animal this material is used for two 

 purposes, for bone construction and for the general metabolism 

 or working of the machine, as for instance, digestion, absorp- 

 tion, circulation, etc. 



Those mineral substances that are gritty, or those that have 

 very sharp edges and corners, assist in destroying worms in the 

 digestive tract. Since mineral matter is used very largely in 

 bone construction, it is clear that a pig during the growing 

 period should have more of this material than after maturity. 

 During the latter time only enough is necessary for mainte- 

 nance or that which is used in the general metabolism or work 

 of the animal machine. 



Sources of Mineral Matter. — Practically all feeds contain 

 some mineral matter but the amount present in different feeds 

 varies greatly. Other sources of mineral matter for swine are 

 the soil itself and the materials pigs are able to get when they 

 roam about on pastures. Pigs may eat some of the soil which 

 supplies various mineral substances. They may eat pebbles, 

 stones, insects, weeds, herbs, etc., all of which may supply an 

 abundance and a great variety of mineral matter. This being 

 true, it is much more important to look after the mineral 

 supply of pigs in winter than it is in summer. If pigs are kept 

 in close confinement the mineral ingredients must be very 

 carefully supplied. 



