BREEDS OF BEEF CATTLE 311 



This ration corresponds with the average requirement of the 

 whole herd, since it is based on its average performance. It hardly 

 need be said that it should be modified to suit the requirements and 

 capacities of the individual cows, the heavy milkers getting more 

 and the lighter ones less. 



By proceeding in this manner, with a little patience there can 

 usually be obtained a ration corresponding as closely as it is neces- 

 sary to the requirement, provided the feeds available admit of it. 

 With a little experience one very soon learns to guess pretty closely, 

 and with some practice finds the computations very easy. An exact 

 agreement with the requirement need not be sought for, since in 

 practice the composition of the feeds will probably vary more or less 

 from the average of the tables. 



The Choice of Feeding Stuffs. When, as in the last example, 

 feeding stuffs must be purchased in order to get the desired relation 

 between the protein and the energy of the ration, it is evident that 

 often a wide range of choice may be offered. In such a case the 

 question at once arises which of the various feeds available is it most 

 economical to purchase, it being evident, of course, that this is not 

 necessarily the one offered at the lowest price. 



No simple method of determining this point is possible, be- 

 cause, as seen, the food serves two entirely distinct purposes in the 

 body. Sometimes the supply of protein is the specially important 

 point, and in other cases what is needed is a supply of energy with- 

 out special reference to whether its source be protein or non-nitrog- 

 enous material. Consequently, the relative values of two feeding 

 stuffs may vary under different circumstances. Some writers have 

 based their comparisons of the values of by-product feeds solely 

 upon their content of protein, for the reason that such feeds are 

 often bought especially to supply this ingredient, while the fats 

 and especially the carbohydrates are usually produced in abundance 

 upon the farm. They regard that purchased feeding stuff as the 

 most economical which furnishes a pound of digestible protein at 

 the lowest cost, ignoring any value in the other ingredients. It is 

 obvious, however, that this is a one-sided view. The other ingredi- 

 ents have a value, and this is especially true in the case of a feeder 

 who buys a considerable part of his grain supply and depends upon 

 it as a source of energy, as well as of protein. The method of com- 

 parison illustrated in the following pages is based primarily upon 

 the cost per unit of energy because this is on the whole the most im- 

 portant function of the feed, but the method takes account also of 

 the amount of protein present. 



Suppose the following feeding stuffs are available to a dairy- 

 man at the prices named : 



Prices of Feeds Per Ton. 



Oats (40 cents per bushel) $25 



Corn meal 25 



Wheat bran 21 



Wheat middlings 24 



Dried brewers' grains 23 



