400 THE FEEDING OF ANIMALS 



number of birds as omnivorous. While seed-eaters like 

 the common fowl are able to subsist for long periods on 

 grain alone, as can also the goose by grazing, the natiu-al 

 food of most young birds is largely animal. Many wild 

 birds which feed abnost entirely on seeds supply their 

 rapidly-growing young with an abundance of animal food. 

 491. Kinds of foods for potiltry. — ^It is a common 

 experience that better success follows the use of several 

 foods combined 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 constituents 

 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 animal food used. When rations 

 of grains naturally lacking in ash-content were supple- 

 mented by bone ash, their efficiency was increased with- 

 out addition of other food. For chicks, during the periods 

 of most rapid growth, the rations of vegetable origin sup- 

 plemented by material rich in phosphate of lime were 

 equal or even superior to rations supplying large quan- 

 tities 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. 



