298 DOMESTIC ANIMALS, DAIRYING, ETC. 



energy which the body can actually utilize requires the use of com- 

 plicated and costly apparatus (respiration apparatus or respiration 

 calorimeter) and the expenditure of much time and labor. While 

 much has been accomplished along this line, vastly more still re- 

 mains to be done before we can claim to have even a fairly com- 

 plete knowledge of the energy values of feeding stuffs. At the same 

 time, enough has already been accomplished, chiefly through the 

 investigations of G. Kiihn and of Kellner at the Mockern Experi- 

 ment Station in Germany, since 1882, and in part also by experi- 

 ments carried on, in co-operation with this Department, by the 

 Institute of Animal Nutrition of The Pennsylvania State College, 

 to demonstrate that the method still generally current of comparing 

 feeding stuffs on the basis of the digestible matter which they con- 

 tain is seriously erroneous and to furnish the beginnings of a reform. 



The last column of the table on page 300 contains the energy 

 values of the feeding stuffs, whose composition is given herein, com- 

 puted on the basis of Kellner's investigations. They are what Kell- 

 ner call production values i. e., they show primarily the value of 

 the different feeding stuffs for the production of gain in mature 

 fattening cattle. Even for this purpose many of them are con- 

 fessedly approximate estimates, and still less can they be regarded 

 as strictly accurate for other kinds of animals and other purposes 

 of feeding. Nevertheless, there seems to be reason for believing 

 that they also represent fairly well the relative values of feeding 

 stuffs for sheep at least, and probably for horses, and for growth 

 and milk production as well as for fattening. At any rate, there can 

 be little doubt that they are decidedly more accurate than the figures 

 which have been commonly used, and we are quite justified in using 

 them tentatively and subject to correction by the results of later ex- 

 periments. 



As regards swine, the matter is far less certain, and it may per- 

 haps be questioned whether the values given in the table are any 

 more satisfactory for this animal than the older ones. 



Feed Requirements. Assuming that the big table on next page 

 represents, with a fair degree of accuracy, the amount of repair 

 material (protein), on the one hand, and of energy, on the other, 

 which the various feeding stuffs can supply, we still need to know 

 how much of each is required by the bodies of animals of different 

 kinds and kept for different purposes ; in other words, we need some 

 formulation of the feed requirements of farm animals. 



Since the animal machine can not be stopped when it is not in 

 active use, it requires, as shown herein, and as is a familiar fact of 

 experience, a continual supply of food. This amount of food, which 

 is required simply to support the animal, is commonly designated as 

 the maintenance requirement i. e., it is the amount required sim- 

 ply to maintain the animal when it is doing no work and producing 

 nothing. In other words, it is the least amount on which life can 

 be permanently maintained. 



The maintenance requirement is naturally greater for a large 

 than for a small animal. Experiment has shown, however, that this 



