ANIMAL FOODS AND FEEDING 297 



were too high. His conclusions and average results are as 

 follows : 



Carbohydrates,'^ chiefly starch and crude fiber, are subject to 

 losses in metabolizable energy due to bacterial fermentation 

 with the formation of methane which is excreted with the faeces. 

 With crude fiber this loss approximates 13.7 per cent of the fuel 

 value of the digested nutrient, even amounting to as much as 

 20 per cent in the case of wheat straw. With 4.184 Cal. per 

 gram as the total fuel value of starch and crude fiber, the above 

 loss reduces this to about 3.6 Cal. per gram. The presence of 

 other carbohydrates (pentosans and some sugars) gives a result 

 from experimental data of 3.761 Cal. per gram as the metaboliz- 

 able or available fuel value for the digestible carbohydrates (em- 

 bracing nitrogen-free extract, crude fiber and pentosans) in 

 ordinary cattle foods. 



Fats 2 do not suffer loss by bacterial fermentation and their 

 metabolizable energy is the same as their fuel value. In 

 analysis, however, the fats are determined as ether extract and 

 this ether extract contains other substances than pure fats, e.g. 

 waxes, chlorophyll, etc., which have a different fuel value and 

 are not metabolized as fats. This results in the metabolizable 

 value of the ether extract being considerably less than the fuel 

 value. The ether extract of meadow hay and cereals has a fuel 

 value of 9.194 Cal. per gram, while the metabolizable energy of 

 the digestible nutrient equals only 8.322 Cal. per gram. 



Proteins ^ with a fuel value of 5.778 Cal. per gram corrected 

 for loss of energy in the urine constituents, as previously ex- 

 plained, have a metabolizable value of digestible nutrient equal 

 to 4.697 Cal. per gram. 



Putting these results together in a table with the equivalents 

 in Calories per pound we have as the best data for the metabo- 

 lizable or available energy of the digestible nutrients in ordinary 

 cattle foods the following : 



1 " Die Ernahrung der landw. Nutztiere," 191 2, pp. 88-gs. 

 2 ;.c., pp. 87-88. 8 /.c, pp. 80-85. 



