NITROGEN FREE EXTRACTS 13 



The nitrogen-free extracts include : 



(a) The carbohydrates, not including crude fiber but only the readily 

 digestible carbohydrates. They are by far the most important nitrogen- 

 free extractives. The other groups may in this respect be practically 

 ignored. Among the carbohydrates should be mentioned starch, non- 

 woody cellulose and pentosanes, dextrin, grape sugar, fruit sugar, cane 

 sugar, milk sugar, malt sugar, etc. 



(b) Several organic acids, 



(c) Nitrogen-free glycosids. 



(d) Bitter principles. 



Nitrogen-free extracts play a most important role in the nutrition of 

 domestic animals. They are the chief nutrient in vegetable feeding stuffs. 

 They constitute the principal and the cheapest source of animal heat, 

 mechanical energy and fat formation. 



a. Carbohydrates 



Starch [(C6Hio05)x] is present in practically all vegetables feeding 

 stuffs. The various grains are especially rich in this nutrient (55 to 75 

 per cent), many Leguminous seeds (45 to 50 per cent) and potatoes (12 

 to 25 per cent; dry, 75 per cent). The starch grains themselves have 

 different forms and structures according to their origin. They take a blue 

 stain with iodin. 



The structure of the starch grains consists of easily digestible granulose 

 (starch proper) and starch cellulose. Starch is characterized by its easy 

 and perfect digestibility. It is used as the standard of feed value in feed- 

 ing stuffs. 



Cellulose (C6Hio05)x is in part very easily digested; thus, the cellu- 

 lose of paper and lint, 70 to 80 per cent ; of hay, 60 to 70 per cent ; of 

 straw and poplar wood, 40 to 50 per cent ; pine wood, 30 to 40 per cent. 

 The ability to digest cellulose varies with the species, being greatest in 

 the ox (30-70 per cent), followed by the sheep (50 per cent), horse (30- 

 40 per cent), and pig (20-50 per cent). In man and in the dog it is prac- 

 tically nil. The more nutritious any particular feed happens to be, the less 

 cellulose is digested of that particular feeding stuff. 



Dextrins iCj^tii2oOio)3> are found in the juices of all young plants, in 

 many seeds, in distillery slops and in feedstuff s rich in starch (potatoes, 

 grains). The dextrins are primary starches and reappear in the digestion 

 of starch as inversion products. Iodin does not stain them a blue color 

 like the starches. Erythrodextrin is stained red with iodin. Fehling's 

 solution (metallic copper salts in alkaline solution) is not reduced by their 

 addition (colored red). 



Grape sugar (CeHigOe) is only rarely foimd in feeding stuffs. Fruit 

 sugar (iCeHigOe) is more widely prevalent, found in sweet plant juices, 

 green rye, etc. Grape sugar (dextrose, glucose) occurs in feeding stuffs 

 as primary cane sugar and primary starch, and during the digestion of the 



