MILK PRODUCTION 415 



moisture which they contain, or to some other difference. 

 Nor should it be overlooked that heifers immature require 

 more protein relatively than mature cows to aid in complet- 

 ing growth, and large milk producers more than those 

 which produce less freely, since with the former more is 

 required for the larger yield of milk furnished. 



Much depends on the relative digestibility of the food. 

 Concentrated foods as grain and the by-products of grain 

 are not only richer in the per cent of nutrients which they 

 contain, but the per cent of these digestible is also larger. 

 This explains in part, why it is advantageous and even 

 necessary to feed more or less grain or meal along with dry 

 fodders. The cow is unable to consume enough bulky 

 fodder to produce maximum milk yields, and with increase 

 in the relative proportion thereof fed to cows, comes in- 

 crease in the energy expended in digesting the ration. For 

 instance, a ration that produces a given return on the basis 

 of nutrients when 60 per cent of the nutrients are digestible, 

 will not produce the same return if but 55 per cent are 

 digestible. Nor should the same return be expected if the 

 nutrients in the less digestible ration were increased so as 

 to make the total digestible nutrients in the two equal. In 

 the latter instance, there would be a diversion of energy 

 in digestion from milk production to the mastication of the 

 extra digestible matter in it, and in carrying the same 

 through the various digestive organs. But, on the other 

 hand, as a matter of economy and to maintain sufficient 

 distension in the digestive organs, a certain proportion of 

 roughage is necessary. 



The necessity for feeding cows freely in milk produc- 

 tion will be apparent when it is remembered that more 

 than half the food fed in many instances is required as 

 the food of maintenance before any return can be obtained 

 for the same. Production can only begin from the food fed 

 after this requirement has been satisfied, and is only limited 

 by the amount consumed and the capacity of the cow to 

 produce milk from it. The only limit to be observed in 



