380 Tlie Feeding of Animals 



bined rather than a few, and it seems to be a fact 

 that some variety is essential. While in practice a 

 combination must be employed for best results which 

 are partly due to the usually greater palatability and 

 other indirect effects on the general health, it is not 

 because of a greater nutritive value of the constitu- 

 ents from different sources that the different foods are 

 needed. The important consideration seems to be the 

 proportion of constituents. In experiments made at 

 the New York Agricultural Experiment Station, the 

 better results from rations containing animal food 

 were found to be largely due to the greater amount of 

 mineral matter, chiefly phosphate of lime, in the ani- 

 mal food used. When rations of grains naturally- 

 lacking in ash content were supplemented by bone ash, 

 their efficiencj' was increased without addition of other 

 food. For chicks during the periods of most rapid 

 growth the rations of vegetable origin supplemented 

 by material rich in phosphate of lime w^ere equal or 

 even superior to rations supplying large quantities of 

 animal protein and fat. For laying hens the time 

 during which such rations were equally efficient was 

 limited to a few months. Rations containing animal 

 food were much superior for ducklings, although the 

 addition of bone ash to rations of grain and other 

 vegetable food notably increased their efficiency. 



Although it is possible, for some purposes, to com- 

 pound effective rations from grain alone when the 

 deficiency of ash is made good, it is l^etter in practice 

 to use some animal food. A variety of grain food 

 supplying enough nitrogenous matter is not always to 



