506 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



physiolog-ical development of animals. It has been sho'WTi, how- 

 ever, that the milk proteins are efficient," that is, they will in 

 the presence of a .sufficienc}^ of non-protein and inororanic nutri- 

 ents, support life, promote growth, and foster all normal phys- 

 iological functions. 



The ash is another food constituent which, though present in 

 sufficient quantities, may not be qualitatively suited to the re- 

 quirements of the animal, but it has also been proved that the 

 ash of milk satisfactorily meets the demands of the young, grow- 

 ing- animal.* In other words, the ash of milk provides in the 

 proper proportions all of the inorganic constituents needed for 

 the proper functioning- of the animal body. 



Still another factor has been recognized as limiting the nutri- 

 tive value of feeds and that is the presence or absence of sub- 

 stances known as "food-accessories," "vitamines, " or "fat-solu- 

 ble A and water-soluble B." These are complex .compounds of an 

 unkno\\ai nature which are antineuritic in action and both are 

 absolutely essential to life. They are found only in minute 

 quantities and many foodstuffs are lacking in one or both of 

 them. It has now been proved beyond doubt that whole milk 

 . contains sufficient of these unknowns to give complete physiolog- 

 ical functioning.' 



Milk, consequently, fulfills both quantitatively and qualita- 

 tively all the chemical requirements of a good ration for mam- 

 malia, but in spite of this fact it can not be successfully used 

 as the sole feed of ruminants at all times. Ruminants are espe- 

 cially adapted to the handling of bulky feeds such as hay, silage, 

 roots and other roughages and begin to use these at a very early 

 age; in the case of calves usually when about three weeksi old 

 and in practice they are generally provided with such roughages 

 as soon as they can consume them. 



In only a few instances have records been obtained of rumi- 

 nants being fed for any considerable time on rations lacking 

 roughage, but Sanborn'' reports that in the case of both sheep aaia 

 cattle fed on grain alone the stomachs weighed less than normal 

 9nd this was most noticeable in the case of the rumen — the 

 stomacli .compartment specially adapted for the handling of 

 bulky material. Davenport^ found that calves could not be raised 

 on a diet consisting of milk alone or grain alone and also noticed 

 that as a rule no digestive disturbances accompanied sueli a 

 ration. 



