The Bulletin. 13 



The following classification will give a clearer understanding of tlie 

 facts presented above : 



-r^ • /Tv-r ^ r.^-. ( True proteins. 

 Protein (N x 6.25) < , ., , 



{ Amido compounds, 



_, .^ , _ ^ . f True fats. 



lats (Jirtner iiiXtract) \ ^^ • • -i ii i i . 



( w a^es, resins, organic acids, cnloropiiyl, etc. 



N'itrogen-free extract. ( Sugars, 



' btarcn, 



Pentosans, etc. 



^ , , , { N'itrogen-free extract. \ g^gars, 



Carbonydrates -^ ^ , %, { btarcn, 



i Crude fiber. j p^^^^^^ 



MICROSCOPIC ANALYSIS OF FEEDS. 



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

 examined miscroscopically. 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 condition, and 

 as this destroys the characteristic appearance of the ingredients, it is 

 very easy to aduterate them with finely ground rice chaff, corncobs or 

 peanut hulls. All of these substances have characteristic elements which 

 are readily distinguished under the microscope. 



For 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 fur- 

 nished by rice chaff or corncobs it would be considered a very low-grade 

 feed. 



DESCRIPTION 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 reason- 

 able limits the standard grades of these by-products have a very sim- 

 ilar 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. 



WHEAT PRODUCTS. 



i?ran.— This consists of the outer portion or covering of the wheat 

 grain. It contains the greater portion of the fibrous material of the 

 grain, but is also rich in protein and fat. Average analyses (104 sam- 



*The analyses used in these descriptions marked (f) 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. 



