56 FORAGE PLANTS AND THEIR CULTURE 



other animals, for which separate feeding trials would 

 need to be conducted. 



48. Chemical analyses. Chemical analyses of feeds 

 usually consider the dry matter as made up of crude 

 protein, that is, the nitrogen multiplied by 6.25 ; ether 

 extract, sometimes called fat, the materials soluble in ether 

 and consisting of fats, resins, chlorophyll and other 

 substances; ash, the mineral matters that remain after 

 incineration of a sample; crude fiber, the portion that 

 remains undissolved after boiling successively in a weak 

 acid and a weak alkali under standard conditions; and 

 nitrogen-free extract, the remaining matter after the above 

 are subtracted, and consisting mainly of starches and 

 sugars. In recent years part of the nitrogen-free extract 

 has been determined as pentosans, while the remainder 

 has been called undetermined. 



Chemical analyses of the same plant species may vary 

 greatly, depending on the soil in which the plant grew, 

 the stage when cut, the amount of irrigation water applied 

 or the presence of fungous disease. Indeed, any factor 

 which affects the growth of the plant also affects its 

 composition. 



In different American analyses of timothy hay the 

 protein content varies from 3.75 to 9.69 per cent, and in 

 European analyses from 4.7 to 10.8 per cent; the ether 

 extract from .97 to 3.98 per cent in American and 1.1 to 

 3.8 per cent in European analyses. 



Chemical analyses can in no sense replace feeding ex- 

 periments in determining feeding values. With a new 

 forage plant a chemical analysis can throw no light on 

 palat ability, digestibility or physiological effect. 



49. Chemical composition as affected by soil fertility 

 and by fertilizers. Extensive experiments on the effect 



