FEEDING GROWING ANIMALS 347 



fifth or more of the total dry substance of the ration for 

 a very young animal. 



445. Food freely appropriated by growing animal. 

 More definite information is furnished by the somewhat 

 limited studies which have been made of the metabolism 

 of the calf. As long ago as 1878 Soxhlet studied the 

 income and outgo of three young calves fed on whole 

 milk. One pound of milk solids, practically all digesti- 

 ble, produced one pound increase of live weight, which 

 was equivalent to a storage of at least one-third pound 

 of body dry substance, a food efficiency for growth prac- 

 tically ten times that exhibited with animals somewhat 

 mature. Nearly 70 per cent of the protein of the food 

 was fixed in the bodies of these calves and only a small 

 proportion was broken down, conditions quite the reverse 

 of those which pertain to the use of food by well-grown 

 steers. Seventy-two per cent of the phosphoric acid and 

 97 per cent of the lime were retained for the purposes of 

 growth. Later experiments with calves fed on rations in 

 whole or in part composed of skim-milk, show a deposit 

 of from 26 to 43 per cent of the protein. These results 

 illustrate the vigor with which a young animal assimi- 

 lates food for growth. The facts show the necessity of 

 feeding young animals on liberal quantities of constructive 

 materials, viz., the proteins and ash ingredients. 



446. Influence of kind of food on the kind of growth. 

 During recent years there has been much discussion 

 and many experiments touching the influence of food 

 upon the development of the animal body. Several 

 experimenters, notably Sanborn and Henry, in this 

 country, have compared the growth of swine on rations 

 presenting extreme differences, as, for instance, mid- 

 dlings and blood against corn meal alone, or shorts and 



