The substances that have nitrogen in them are called protein.  They are very complex and difficult to analyze.  In digestion these proteins are all torn to pieces and built up into other kinds of protein.  Just as in tearing down an old house, only a portion of the material can be used in a new house, so it is with protein and laboratory analysis cannot tell us how much of the old house can be utilized in building the new one.

In practice the whole subject simmers down to the proposition of finding out by direct experiment whether the hen will do the work best on this or that food, irregardless of its nitrogen content as determined in the laboratory.

The results of many experiments and much experience has shown that lean meat protein will make egg protein and chicken flesh protein and that vegetable protein pound for pound is not its equal.  I know of no results that have proven that the high priced vegetable foods such as linseed meal, gluten feed, etc., have proven a more valuable chicken food than the cheapest grains.

With cows and pigeons this is not the case, but the hen is not a vegetarian by nature and high priced vegetable protein doesn’t seem to be in her line.  Of the three standard grains there is some indication of the value of the proteids for chickens and of the following ranks, 1st oats, 2d corn, 3d wheat.

The false conceptions of the value of wheat proteids has been specially the cause of much waste of money.  Digestive trials and direct experiments both show that, as chicken foods, wheat is worth less, pound for pound, than corn and yet, though much higher in price, it is still used not only as a variety grain, but by many poultrymen as the chief article of diet.  Wheat contains only 3 per cent. more proteid than corn.  The man who substitutes wheat at one and one-half cents a pound for corn worth one cent a pound pays 17 cents a pound for his added protein.  In beef scrap he could get the protein for 5 cents a pound and have a very superior article besides.

Milk as a source of protein ranks between the vegetable proteids and those of meat.  It is preferably fed clabbered.  The dried casein recently put on the market is a valuable food but is not worth as much as meat food and will not be extensively utilized until the demand for meat scrap forces up the price to a point where the casein can be sold more cheaply.  Meat scrap, to be relished by the chickens, must not be a fine meal, but should consist of particles the size of wheat kernels or larger.  The fine scrap gives the manufacturer a chance to utilize dried blood and tankage which is cheaper in quality and price than particles of real meat.

The last and least understood of the groups of food substances is mineral substance or ash.  Now, the chemist determines mineral substance by burning the food and analyzing the residue.  In the intense heat numerous chemical changes take place and the substances that come out of the furnace are entirely different from those contained in the fresh food.