156 THE FEEDING OF ANIMALS 



animal is given food free from the compounds of the 

 mineral elements, the animal suffers physical deteriora- 

 tion and finally dies. In considering the matter of a 

 sufficient supply of mineral element, the feeder should 

 consult tables showing the ash composition of the various 

 feeding-stuffs. 



227. Supply of mineral elements (see Pars. 48-54). 

 The supply of the mineral elements in the food of the 

 various classes of animals has not until a comparatively 

 recent time received extensive consideration. It has been 

 practically held that nature has made a generous provision 

 for supplying the animal's needs for mineral substances 

 in our home-raised feeding-stuffs and that mixed rations 

 as usually fed contain in variety and quantity all that is 

 needful of these nutrients for the various kinds of pro- 

 duction. It was clearly proved .sometime since that an 

 extra supply of mineral compounds is needed for laying 

 hens, especially calcium compounds for the formation 

 of egg shell, and it was also shown that the proper devel- 

 opment of the bony structure of swine is not secured 

 through feeding cereal products alone, particularly exclu- 

 sive corn-feeding, but the mixed rations for bovine pro- 

 duction have not been questioned in this direction. 



It has remained for Forbes in a recent extensive and 

 exceedingly important investigation as to the mineral 

 supply of liberally producing cows to show that during 

 full milk production, even when the animals were fed 

 on rations that are regarded in practice as highly satis- 

 factory, there were important losses of calcium, mag- 

 nesium, and phosphorus from the cow's skeleton. It is 

 suggested that the decreasing milk-supply during a 

 given period of lactation and the sometimes observed 

 failure of a highly producing cow to carry her high pro- 



