326 NUTRITION OF FARM ANIMALS 



No similar comparisons of the protein requirement appear to 

 have been made. Since, however, the minimum protein re- 

 quirement does not represent a demand for energy but for 

 certain specific substances required for the normal functioning 

 of the body, it seems plausible to suppose that its amount will 

 depend rather upon the mass of active tissue than upon the body 

 surface. If such be the case, the protein requirement may, 

 with sufficient accuracy for practical purposes, be computed in 

 proportion to the live weight and that course is followed in 

 the succeeding paragraphs. 



415. Protein requirement of cattle. For obvious reasons 

 it is impracticable to ascertain the fasting katabolism of rumi- 

 nants as a basis for estimating their maintenance requirement 

 as regards protein, but by a comparison of the recorded experi- 

 ments in which the nitrogen balance upon small amounts of feed 

 has been determined it is possible to fix approximately the limit 

 of protein supply below which, even in the presence of an abun- 

 dant supply of non-nitrogenous nutrients, a loss of body protein 

 occurs^. 



Of the investigations upon the energy requirement for main- 

 tenance summarized in Chapter VIII (381) only those of Kellner 

 and the live weight experiments of the writer, together with 

 the early results of Henneberg and Stohmann, afford data 

 regarding the minimum protein requirement. While protein 

 maintenance was probably secured in the remaining instances 

 there is no sufficient evidence to show that a surplus of protein 

 was not being consumed (402, 411). In addition to the foregoing, 

 the investigations by the Laboratory for Agricultural Research 

 in Copenhagen l upon the protein requirements for milk pro- 

 duction (586) also afford approximate data as to the main- 

 tenance requirement, and Fingerling, 2 in experiments upon the 

 protein requirements of growing calves (471), obtained inter- 

 esting indications regarding the quantity required for main- 

 tenance. 



The lowest recorded amounts per 1000 pounds live weight 

 upon which nitrogen equilibrium was reached were 0.21 pound 



1 Denmark-Beretning fra den Kgl. Veterinaer of Landbohojskoles Laboratorium 

 for landokonomiske Forsog. 6ode, 1906, and 63de, 1907, Kobenhavn. Translated 

 by Mallevre, Societe de 1' Alimentation Rationelle du Betail. Compte Rendu de 

 neme et i2eme Congres. 



2 Landw. Vers. Stat., 76 (1911), i. 



