Food Requirements of Animals. 265 



necessary for economical milk production at from 15.5 to 16.5 

 pounds per day for a good cow of average size. The quantity re- 

 quired may va,ry somewhat according to size, a small cow re- 

 quiring proportionately somewhat more than a larger one for the 

 same yield of milk, but capacity for production is the more im- 

 portant factor in determining the quantity of feed required. 

 With that amount of digestible nutrients, the nutritive ratio 

 would be about 1 :9.5. Careful experiments, however, show that 

 a nutritive ratio of 1 :5.5 to 1 :6.5 is more efficient than the wider 

 one, and that a cow of average size and good capacity should re- 

 ceive at least 2.25 pounds of digestible protein daily, with a nu- 

 tritive ratio not wider than 1 :6.5. Young pasture grass, well 

 known to be an efficient milk producer, is even narrower than this. 

 The function of this additional protein is not known, but the ac- 

 cepted axiom that proteins stimulate the metabolic activities of 

 the cells is borne out here, with an intensified milk secretion as 

 the result. On the other hand, excessive protein feeding may 

 be injurious and certainly is not necessary. 



It has been taught that the fats of milk originate from the 

 protein and food fats. If true, this would increase the demand 

 for protein, but experiments have clearly demonstrated that they 

 are not a necessary source of milk fat. In a carefully conducted 

 experiment at the New York Experiment Station, Jordan con- 

 clusively showed that the carbohydrates of the food could serve 

 as milk-fat formers. 



The food consumed by the dairy cow during the first half of 

 the lactation period is largely used in milk production, but during 

 the latter portion of lactation it is partly consumed in building 

 the calf, and the return in milk is reduced. A newly-born calf 

 weighing 80 pounds, may contain 20 pounds of protein, 3 pounds 

 of fat, and the rest will be water and ash. 



From what has been said on the necessity of a proper protein 

 supply for the milch cow, it is apparent that where the home 

 grown crops are the hays made from true grasses and where the 

 corn crop is the chief one raised, then home-grown rations for 



