582 



NUTRITION OF FARM ANIMALS 



By-products 



692. Nature. The by-product feeding stuffs are the resi- 

 dues of technical processes by which the products of the soil 

 are prepared for man's use, either as food or for other purposes. 

 The more important of these technical processes are : the mill- 

 ing of grains ; the manufacture of cereal foods ; the manufac- 

 ture of alcoholic liquors ; the manufacture of starch and glu- 

 cose ; the manufacture of sugar ; and the extraction of oils. 



693. By-products of milling. Milling residues, particularly 

 of wheat, are among the most familiar of the by-product feed- 

 ing stuffs. They include the screenings secured in cleaning the 

 grain for milling and the bran and middlings secured in the 

 grinding proper. The screenings are an exceedingly variable 

 mixture according to the quality of the grain, containing, be- 

 sides light and broken grains, a great variety of weed seeds, 

 fragments of straw, sand and earth, as well as spores of numer- 

 ous fungi, and dirt of all sorts. While some of these have un- 

 doubted feeding value, the possible danger to the health of the 

 animals, and of the infestation of the fields with weed seed 

 through the manure, demand great caution in the use of 



screenings as feed. Its ad- 

 dition to bran or middlings 

 is to be regarded as an 

 adulteration. 



Bran. The bran of wheat 

 or rye consists essentially of 

 the seed-coats of the grain, 

 the layer of so-called gluten 

 cells immediately beneath 

 them, and a proportion of 

 the inner, floury part of the 

 grain varying with the per- 

 fection of the milling. The 

 seed-coats of the grain con- 

 tain most of its crude fiber, 

 while the gluten cells are 

 richer in proteins than the inner part of the kernel. In pro- 

 portion, therefore, as the bran is more perfectly separated from 

 the flour, does it become at once richer in protein and in crude 



FIG. 43. Partial section of wheat grain. 

 (Bailey's Cyclopedia of American Agricul- 

 ture.) 



i, Seed pod. 2, Outer seed coat. 3, Inner seed 

 coat. 4, Gluten cells. 5, Starch cells. (Jordan.) 



