THE FEEDING OF DAIRY COWS. 11 



the production of body tissues, heating the body,, performing bodily 

 functions, such as digesting feed, moving from place to place, and for 

 milk production. For the purposes of the present discussion, it is 

 sufficient to say that the constituents or compounds and the relative 

 quantities necessary for these operations have been determined; that 

 is, we know that milk contains protein and energy or heat-producing 

 constituents, the protein being represented by the casein and albumin 

 and the energy and heat-producing constituents by the fat and sugar. 

 In addition to the constituents or compounds necessary for the pro- 

 duction of milk, she also must have the constituents necessary for 

 performing the other functions mentioned. These, for convenience, 

 have been classified into proteins, carbohydrates, and fats. Fats per- 

 form much the same functions as carbohydrates and are worth for 

 production practically two and one-fourth times as much per pound 

 as carbohydrates, and in the balancing of a ration are usually classed 

 with them. This brings us to a definition of a " balanced ration," 

 which is a ration containing these various nutrients in the proportion 

 the cow needs them. 



The economical importance of a balanced ration is evident. The 

 cow can use only certain elements or compounds in certain propor- 

 tions ; consequently, if the ration supplies an excessive amount of any 

 one, the excess is liable to be wasted. Not only is this true, but as 

 the cow has to assimilate it even though she can not use it, her capacity 

 for production is reduced. 



COST. 



In making a ration, cost is one of the important factors. The 

 best practice is to compound a grain mixture so that it will balance 

 with the home-grown roughage. With this in mind, the separate 

 grains should be selected to supply the necessary nutrients at the 

 lowest possible cost. For this, not only the price per hundred pounds 

 but also the relative cost of each constituent, especially protein, must 

 be considered. For example, to determine the cost of a pound of 

 digestible protein in a given feed divide the price of 100 pounds by 

 the per cent of digestible protein in the feed. If this calculation is 

 made for several feeds, the relative cost of protein in each will be 

 apparent. Then the feeds that furnish protein at the least cost can 

 be selected. The same can be done to determine the cost of the carbo- 

 hydrates and fat, which are the heat-making or energy-producing 

 part of the feed. 



BULK. 



A certain bulk is necessary in the grain mixture to obtain the best 

 results. When heavy feeds are used, some bulky ones should be in- 

 cluded to lighten the mixture, since it is probable that a certain degree 



