THE FATTENING OF MATURE ANIMALS 365 



supplied to fattening animals may be approached much as was 

 the question of- the amount necessary for maintenance in Chap- 

 ter IX, i.e., by inquiring what is the least amount of digestible 

 protein which, along with sufficient non-nitrogenous nutrients, 

 has sufficed to support a satisfactory rate of fattening. If it 

 appears that of two similar animals or lots of animals receiving 

 equal amounts of feed, the one consuming the smaller amount 

 of protein gave equally satisfactory gains, both as judged by 

 the live weight and by the block test, it may be concluded that 

 the smaller amount of protein was at least sufficient, although 

 it cannot be determined whether it may not have been greater 

 than was actually necessary. 



Unquestionably, the protein requirements of mature fatten- 

 ing animals have been greatly overestimated in the past. Wolff's 

 original feeding standards (791), published in 1864, recommended 

 for fattening rations per thousand pounds live weight the follow- 

 ing amounts of digestible protein : 



Cattle 2.5-3.0 Ib. 



Sheep 3-0-3-5 lb- 



Swine 2.7-5.0 lb. 



Substantially these same figures have been repeated more 

 or less uncritically from publication to publication, with a few 

 exceptions, even up to the present time. It is clear, however, 

 from Wolff's writings that his standards were based upon the 

 then prevailing views of Voit and Pettenkofer (248) regarding 

 the importance of protein as a source of animal fat rather than 

 upon actual experimental results. Subsequent investigations, 

 notably the respiration experiments of Kellner upon cattle 

 (p. 367), have fully demonstrated that such large amounts of 

 protein are neither necessary nor especially advantageous for 

 fattening. 



Sheep. Indeed, Wolff himself has demonstrated that his protein 

 standard for sheep was unnecessarily high. In 1890, he published 1 

 the results of a comparison made in 1885-1886 of maize and beans as 

 feed for fattening sheep, using two lots of two mature sheep each. 

 After a preliminary feeding, the following results were obtained in 

 107 days' feeding : 



1 Landw. Jahrb., 19 (1890), 823. 



