90 A STUDY OF FARM ANIMALS 



and to the great profit of those adopting them. Probably 

 no class of people has studied the standard more carefully 

 than feeders of dairy cattle, and it is among herds of this kind 

 that we find Wolff -Lehmann standards most commonly used. 

 It must be understood that one may not be able to feed one's 

 stock so as to follow the standard perfectly, but there is no 

 trouble in using it in a practical way as a guide. One may 

 without difficulty feed within the limitations of the standard. 

 When the animal is fed about right, according to the stand- 

 ard, then a balanced ration is being used, or one which, 

 without waste, most perfectly meets the needs of the body. 

 Many experiments have shown that the balanced ration can 

 be relied upon for giving the best results. 



Energy value feeding standards have recently attracted 

 attention. Kellner, a German, and Dr. H. P. Armsby, a 

 noted American investigator of feeding animals, about 1908 

 proposed that the feeding value of foods be measured by 

 their energy contents, as shown by the therms of net energy 

 they supply. These men accounted for the loss of a part of 

 the food energy by the animal in the mastication of its food, 

 and in the operations of the internal organs, etc. The energy 

 left after digestion they called the net energy and this was 

 used by the animal for supplying special needs. Armsby has 

 published a set of figures showing the dry matter, digestible 

 protein, and net energy value in therms in some of the most 

 common feeding stuffs. He has also prepared a maintenance 

 ration standard, and one for growing cattle and sheep. The 

 following is made up from the latter, to show how this energy 

 standard is arranged. 



CATTLE 



Age Live weight Digestible protein Net energy value 



3mos. 275 Ibs. 1.10 Ib. 5.0 therms 



12mos. 650 Ibs. 1.65 Ib. 7.0 therms 



24 mos. 1000 Ibs. 1.75 Ib. 8.0 therms 



This table shows that a calf three months old and weigh- 

 ing about 275 pounds requires 1.1 pound of digestible pro- 



