DEFINITIONS AND TECHNICAL CONSIDERATIONS. 349 



by the addition of fat to a fodder. It is important to use fatty substances in 

 moderation, otherwise ruminating animals soon lose their appetites; this is 

 more particularly the case when oil is added to a fodder, and is not true to the 

 same extent when the crude fat of a by-fodder is considered. Some German 

 experiments prove that 100 grams per diem may be fed without influencing 

 the weight of an animal one way or the other. 



The best proportion between fats and protein is claimed by some to be 



Fats 1 1 



Protein ~ 2. 2 r 3 



Experiments appear to show that beyond 1-2.2 the fats simply pass into the 

 excrements without being utilized. 



CruLius's experiments appear to show almost conclusively that the increase 

 in weight of a sucking calf does not depend upon the protein or milk sugar, 

 but upon the butter contained in the milk of the mother. This should be 

 about 5 per cent, of total milk drunk. 



Henneberg and Stohmann's experiments also show that the crude fatty sub- 

 stances contained in a coarse fodder are not equally digestible in all fodders, 

 and that it is not well to assume that more than 1-3 is assimilated; the amount 

 to be added consequently increases with the quantity of concentrated fodders 

 used in a ration. 



Investigations relating to the digestibility of fats are not as accurate as those 

 upon albuminoids. Several sources of error constantly occur, due to the fat 

 found in excrements that comes from the bile, which, if not deducted, would 

 lead to the supposition that the fat was less digestible than it actually is. 

 This source of error is slight when the fodder contains considerable fat, but is 

 great when the original percentage was low. 



Digestibility of fibre. To estimate the amount of cellulose digested is more 

 difficult than one might suppose. If the percentage of crude fibre found in 

 the fodder fed and excrement obtained be reduced to pure cellulose and lignin, 

 based upon their percentage of carbon, and one result subtracted from the 

 other, the amount obtained representing digestibility would be much higher 

 than the reality. However, from a practical point of view this method 

 answers every purpose. The most important investigations relating to digesti- 

 bility of cellulose are those of Henneberg and Stohmann. It has been con- 

 cluded that 30 to 70 per cent, of crude fibre is digestible, depending upon the 

 animal and manner of feeding. Pure cellulose contains about 44 per cent, of 

 carbon or about the same as starch, and it is mainly in this state that it is 

 assimilated. Owing to the excessive length of their intestinal canal ruminants 

 have a special facility for digesting crude cellulose. In the experiments men- 

 tioned in the foregoing, in which it was found that oat straw had a coeflicient 

 of digestibility of 0.44, wheat straw 0.39, clover hay 0.67, etc., the protein 

 had an important influence. Weiske's experiments upon sheep appear to 

 show that the cellulose dissolved during the last stages of digestion had very 

 little effect towards economizing albumin during the process of assimilation. 



