i8o THE CHEMISTRY OF CATTLE FEEDING 



Cost of Production. The influence of the food on milk 

 production, when regarded from a commercial standpoint, 

 requires careful consideration. The question is a difficult 

 one to investigate theoretically, owing to the fluctuation in the 

 prices of the feeding stuifs and of the milk produced. The 

 case of a farmer who grows hay, roots, corn, and beans, and 

 sells the milk at 6d. or &/. per gallon, is very different from 

 that of a town dairyman who has to purchase everything, but 

 who realises from is. to is. $d. per gallon for his produce. 

 The following calculations are to be regarded merely as illus- 

 trating the method of investigation. 



The more important points to be considered are : (i) Each 

 cow requires a certain ration simply for maintenance, whether 

 she produces milk or not; (2) additional food is required for 

 milk production ; (3) the larger the yield, the greater is the 

 amount of additional food required, both absolutely and rela- 

 tively. 



If the amount of additional food required for milk pro- 

 duction were directly proportional to the yield or even 

 approximately so it is obvious that a yield of two gallons 

 would afford a much larger profit than a yield of one gallon, 

 and so on, because the cost of the maintenance ration must 

 be added to that of the additional food in both cases. But 

 this is not so. The second gallon costs more to produce it 

 than the first, and the cost of production of each successive 

 gallon increases progressively. A point must ultimately be 

 reached, therefore, beyond which any further increase in the 

 yield would cease to be profitable. An example will make 

 this clear. 



For simplicity, the maintenance ration may be supposed 

 to consist entirely of hay, of which 19 Ibs. would be required 

 for a cow of 1000 Ibs. live weight. If this fodder can be 

 bought or produced for 65^. per ton, the cost of the main- 

 tenance ration would be 6\d. per head per day. 



Let it be further supposed that the additional food for 

 milk production consists of a mixture of decorticated cotton 

 cake and maize, and that each of these substances costs 8 

 per ton. Two parts of cake to one of maize would give about 



