514 



Journal of Agriculture, Victoria. [11 Sept., 1916. 



percentage of crude fibre increases, tlius rendering digestion both more 

 costly and slower. The more slowly digestion proceeds the greater 

 will be the loss from fermentation. 



The cost of digestion must not be confused with the digestibility of 

 a food. 



Digestibility regulates the proportion digested, which is the difference 

 between the amount consumed and the solid manure. The cost of 

 digestion is a charge made against the food in changing it from the 

 undigested to the digested condition. 



The above table must not be used to compare the relative values of 

 the foods included. It serves only to compare the amounts of food 

 substances — reduced to a starch equivalent — in the original food with 

 that which is available for use of the animal. 



Using as an illustration the two extremes — oats and oaten straw — it 

 will be noticed that from 99 starch equivalents in oats, 64, or 64 per 

 cent., represent net gain; 82 starch equivalents in oaten straw, 16, or 

 19 per cent., represent net gain. 



In the case of the former, 34 per cent is not available, due partly to 

 a portion being indigestible, and partly to the energy consumed in 

 digestion, whilst the latter shows a loss of 71 per cent, from the same 

 causes, but largely owing to the heavy expenditure in digestion. 



A striking example is afforded in the following, which demonstrates 

 the value of silage, and provides a reason for what has frequently been 

 proved in practice : — 



Original Foodstuffs. 



ISTet Amount Available for Nutrition. 



Oaten hay 

 Oaten silage 



Digestible — Cost of Digestion. 

 Protein. Carbohydrate. 



2.5 26 



1.6 17 



Fat. 

 2.0 



Starch equivalents. 

 30 

 20 



