THE DIGESTIBILITY OF DRIED YEAST. 



By CHARLES CROWTHER and HERBERT ERNEST WOODMAN. 



{Institute for Research in Animal Nutrition, 

 The University, Leeds.) 



At the close of the digestion experiments described in the foregoing 

 communication a quantity of the "seeds" hay of known composition 

 and digestibihty remained which was sufficient for one further experi- 

 mental period. The opportunity was therefore taken of determining 

 the digestibility of dried yeast, a by-product of the fermentation in- 

 dustries which is being produced in increasing quantities and which 

 has attracted notice since the outbreak of war. 



Material which was being given to stock on the farm (Manor Farm, 

 Garforth) was used for the purpose, and only when the test was well 

 under way was it discovered that this consignment, although apparently 

 of normal character, was considerably poorer in protein (32-5 %) than 

 the general average of dried yeast on the market (45 %). It is unfor- 

 tunate that for this reason there may be some doubt as to the general 

 apphcability of the results, but as will be indicated later there is good 

 reason to think that they may be so apphed. 



The general arrangements for the test were identical with those 

 previously described and the same two sheep were employed for the 

 purpose. 



Each sheep consumed exactly the same quantities of hay and yeast, 

 the average daily ration being 446 gms. hay and 300 gms. yeast, this 

 representing a supply of 476 gms. " starch equivalent," including 142 gms. 

 protein, or a nutritive ratio of 1 : 3-2. 



The dried yeast used contained 11-70 % moisture, 32-45 % crude 

 protein (including 27-54 % true protein), 0-41 % ether extract, 45-43 % 

 nitrogen-free extractives, 1-94 % crude fibre and 8-07 % ash. 



Considerable difficulty was experienced in inducing the sheep to 

 eat the desired amount of yeast at the outset, and for this reason the 

 actual periods for the two sheep were not concurrent, the experimental 

 period (12 days) of Sheep 2 being from June 27 to July 8, 1916, whilst 

 that for Sheep 1 was not secured until July 18th to 29th. 



