VARIATIONS IN COMPOSITION 137 



Of all the ash constituents lime and soda are prob- 

 ably the most generally deficient. Maize is of all 

 ordinary foods (rice excepted) the poorest in lime ; it 

 certainly contains too small an amount for a rapidly 

 growing animal. In the United States it has been 

 found advantageous to give wood ashes or ground 

 bones when maize is used alone as a pig food. Growing- 

 pigs required 517 lbs. of maize meal to produce 100 lbs. 

 of increase, but 466 lbs. sufficed when wood ashes were 

 added ; the breaking strength of the thigh bones was 

 also more than doubled by this addition to the food. 

 Animals will frequently receive no inconsiderable 

 amounts of lime in their drinking water. Soda is 

 easily supplied, when needed, in the form of common 

 salt (see p. 154). 



Circumstances producing Variation in Composition. 



— The composition of all vegetable foods is liable to 

 variation, depending on the variety of plant grown, its 

 state of maturity, and the character of the soil, manure, 

 and season. The influence of the variety grown is well 

 illustrated in the case of oats, the different varieties of 

 which will differ much in composition. The perfectly 

 matured produce of any plant, the ripe seed for 

 instance, will not generally vary much in composition 

 under the ordinary conditions of climate and manuring, 

 and an average composition, such as is given in the 

 table, will be found in most cases pretty correct. 

 Great variations in climate may, however, determine 

 considerable changes in composition. South Russian 

 wheat is, for instance, far more nitrogenous than 

 English wheat. When, however, we turn to immature 

 produce, such as meadow grass, turnips, or mangels, 



