10 The BuLLETiisr. 



The following classification will give a clearer understanding of 

 the facts presented above : 



Protein (Nx 6.25) I T^^\^P^'^^^^^'- , 

 ^ ^ t Ami do compounds. 



f J_ nip TJits 

 Fats (Ether Extract) -^ ttj * • • -j i,i i, i 4. 



^ ^ { Waxes, resins, organic acids, chlorophjl, etc. 



/ AT-x J- . . i Sugars, 



n„,.i.^u,,.i,.„f„ JN itrogen-±ree extract. ' o^ 1 



(Jarbohydrates i r^ t^ m "\ Starch, 



Crude fiber. I ry ^ 4. 



' Jrentosans, etc. 



MICROSCOPIC ANALYSIS OF FEEDS. 



In addition to the regular chemical analysis, all the feed samples 

 are examined microscopically. This is the final test of their purity. 



The chemical analysis shows the percentage amounts of the 

 nutritive constituents of the feed, but it gives no idea of the source 

 from which they are derived, and as the protein and fat are more 

 digestible and hence more valuable in some classes of feeds than in 

 others, it is very important to know just what substances go to make 

 up the feed. The microscopic examination is the only way this can 

 be done with any degree of accuracy. 



The chief use of the microscope in feed analysis is in the detection 

 -of adulterants and in the detection of the use of spoiled or low-grade 

 seeds. Many feeds are now put on the market in finely ground con- 

 dition, and as this destroys the characteristic appearance of the 

 ingredients, it is very easy to adulterate them with finely ground 

 rice chaff, corncobs or peanut hulls. All of these substances have 

 characteristic elements which are readily distinguished under the 

 microscope. 



Eor example, if a mixed feed contains 15 per cent of fiber it would 

 not be considered low grade, provided it is made from good materials ; 

 but if the microscopic examination shows that part of this fiber is 

 furnished by rice chaff or corncobs it would be considered a very 

 low-grade feed. 



DESCRIPTIOX AND COMPOSITION OF THE BY-PRODUCTS USED 



FOR FEED. 



The materials used for commercial feeds are usually the by- 

 products of other industries, such as the by-products from flour mills, 

 oil mills, etc. The composition of these materials varies somewhat 

 with the season in which they are grown, the method of milling, 

 etc.; but within reasonable limits the standard grades of these by- 

 products have a very similar composition. The following general 

 descriptions of these products, with the average analyses, compiled 

 from a large number of analyses', will show what the compositions 

 of each one of these products should be. 



•The analyses used In these descriptions marked (t) are taken from Bulletin No. 11, Office of 

 Experiment Stations, U. S. Department of Agriculture. Those not so marked are compiled from 

 analyses made In this laboratory. 



