Food Requirements of Animals. 263 



richness in sulphur, which we have seen constitutes a considerable 

 proportion of the pure wool fiber. 



Requirements for milk production. Milk ultimately comes 

 from the food and its direct purpose is for the nutrition of the 

 young. For this reason its production, so far as possible, is made 

 independent of the immediate food supply. If the surplus food 

 given a fattening ox is withdrawn to a maintenance requirement, 

 the laying on of increase will immediately cease ; but the food of 

 a milking cow may be reduced to maintenance, without stopping 

 the production of milk. The animal will continue to produce 

 milk, drawing for its source from her own body. The quantity 

 produced will decrease and the animal will steadily grow thinner. 

 A minimum food supply will not entirely stop milk production, 

 neither will an over-abundant supply raise the milk production 

 beyond certain limits. Each cow has an inherent milk producing 

 capacity, determined by breed and individuality. Above this it 

 is rarely possible to go, but whether this capacity is reached will 

 depend upon food and treatment. Excess of food will simply 

 tend to fatten. Generous feeding will not make a good milch cow 

 out of a poor one, but it will sustain a full flow of milk and extend 

 the period of profitable production. 



There is only one way to determine whether a cow is profitable, 

 and that is by determining her yield of milk and the amount of 

 marketable constituents it contains. To-day, this is entirely done 

 on the basis of the quantity of fat the milk contains, which gives 

 the animal's capacity for butter production. To measure the 

 capacity of her milk for cheese production, both fat and casein 

 must be determined. From the standpoint of economy in trans- 

 forming feed stuffs into human food, the total milk solids, and 

 not the milk volume, should be the basis for estimation. 



The quantity of nutrients necessary to make 100 pounds of 

 Jersey milk, other things being equal, is greater than that re- 

 quired to produce the same weight of Holstein milk. From the 

 standpoint of the farmer the most profitable cow is the one pro- 



