THE COMPUTATION OF RATIONS 695 



That the requirements there tabulated resemble more or less 

 the earlier feeding standards and share to some degree their 

 limitations is undeniable and likewise unavoidable. No finite 

 number of formulas, however accurate, can cover specifically 

 all the various conditions of practice, and in particular it is 

 scarcely possible for them to include any consideration of the 

 financial aspects of the matter. The most that seems possible 

 is, first, to formulate the average requirements under ordinary 

 circumstances and then to indicate as definitely as present 

 knowledge permits, as has been attempted in Chapters VII- 

 XIV, the influence of various conditions in modifying these 

 requirements. The difference between the older and newer 

 formulas lies far more in the point of view than in the com- 

 pleteness or exact numerical accuracy of the figures and neither 

 can be utilized as infallible recipes which shall spare the user 

 the trouble of observing and thinking. 



798. Defects of the tables. That not a few of the estimates 

 of feed requirements contained in the Tables of the Appendix 

 rest on quite meager data is apparent from the discussions in 

 Part III. This is particularly true of the requirements for 

 growth, as will be evident from a study of Chapter XI. To a 

 somewhat less degree the same is true of those for milk pro- 

 duction, the energy requirements in particular being based on 

 an hypothesis regarding the cause of the higher net energy 

 values for milk production (593, 605) which has not yet been 

 submitted to experimental test. 



The estimates of the protein requirements are particularly 

 unsatisfactory for two reasons. 



In the first place, they virtually assume all proteins to be of 

 equal value. That such is not the case has been repeatedly 

 stated in previous pages, but it has also been shown that 

 present knowledge of the constitution of the vegetable proteins 

 and of the amino acid requirements of the body is insuffi- 

 cient to serve as the basis of a more satisfactory system. 



In the second place, there has been very little systematic 

 investigation of the minimum protein requirements of farm 

 animals for different purposes or of the percentage of different 

 proteins capable of utilization for the production of body pro- 

 tein or of milk protein. The requirements given in the 

 tables are, to a large extent, based on observations in practice, 



