MANUAL 0¥ CATTLE-FEEDING. 235 



quantity and quality of tlie erude fibre lias an influence on 

 its digest! bilit}^ 



Formulae for DigestilDility of Protein. — ^As we have 

 seen, the digestibility of the non-nitrogenous matters of a 

 coarse fodder, with the exception of the small quantity of 

 fat which it contains, can be estimated from the results of 

 analysis with sufficient accuracy for practical purpose^ al- 

 though not with scientific exactness. 



Unfortunately, we have no such simple means of esti- 

 mating the digestibility of the crude protein, although the 

 attempt has more than once been made to supply one in 

 the shape of a fornmla which should enable us to deter- 

 mme the digestibility of the crude protein of a fodder or 

 of a ration by calculations based on its composition. These 

 formulae arJ, of course, all enipiricaJ, being founded on the 

 results of as many feeding experiments as possible. 



In view of the importance of protein in nutrition, and 

 the great variability which experiment has shown to exist 

 in its digestibility, the advantages to be derived from a 

 correct formula of this sort are manifest. Nevertheless, 

 none of the various formulae which have been proposed 

 have met with much favor, and it seems to be the opinion 

 of the best authorities that it is yet too soon to attempt 

 their formation. 



All these formulse aim to express the influence of the 

 ehsinieal eomposlUon of the fodder or ration on the diges- 

 tibility of its protein — an influence which, though an im- 

 portant one, is by no means the only factor involved. As 

 regards coarse fodder alone, they offer little advantage 

 over the intelligent use of " digestion coefficients," and the 

 less since the results obtained by their aid sometimes vary 

 widely from the truth. In the case of a ration ineludiug 

 considerable concentrated fodder, they seem to yield more 



