116 POULTRY-CRAFT. 
155. Use of Feeding Standards.— The practical value of a scientific 
knowledge of feeding is that it enables a feeder to make up his ration ‘‘in the 
rough” with absolute certainty that he has made no radical error —none that 
will not in the natural course of things soon be adjusted. A ration based on 
(not necessarily adhering rigidly to) a correct standard is, in the hands of 
a skillful feeder, practically self-adjusting. The calculations of values in 
approved rations show that for ordinary purposes variations from the standard, 
if made at all, need be but very slight; for the differences between supply and 
demand are not usually greater than will be controlled by the involuntary 
adjustments of the natural checks and balances, viz.:— the limited capacity of 
the digestive organs; the sense of taste, the instincts of hunger, the natural 
cravings of a healthy appetite for the food articles best suited to meet present 
requirements of the system; the convertibility of the principal food elements ; 
the ¢endency of the fowl’s system to make the most of the food taken, expend- 
ing some in egg production, using some for growth, storing some as fat, 
squandering some as exuberant energy — these are all constantly working to 
bring about a proper balance of means and results, and the feeder’s part must 
be very badly done, indeed, if they fail. 
156. Extent of Actual Variations, from the Standards, in Complete 
Rations.— The system’s demands for material for growth, or maintenance, 
and strength, are, on the whole, very nearly constant for mature fowls, and 
uniformly increasing for chicks. Fluctuations in food requirements are due 
principally to variations in the amount of heat required to keep the body warm. 
The standards of ratio and energy ascertained are for average conditions, such 
as obtain generally in moderate weather, and in warm houses in cold weather. 
Under such conditions the values of the grain ration are the values of the 
whole ration, the small quantities of vegetables and meat eaten affecting it but 
little. In summer the food actually consumed by a properly fed fowl would 
have a narrower nutritive ratio than 1:6, and potential energy !ower than 100. 
The reduction would follow reduction in the quantity of the grain ration, and 
large increase in the quantity of vegetables eaten, and would be governed 
solely by the appetites of the fowls. In winter the heat of the body is 
maintained partly by feeding more heating foods, but mostly by warm housing 
and by giving the food and drink warm. The actual variation of a ration from 
narrow nutritive ratios are bulky foods, diluted either with water or with fiber. Jow 
potential energies are for hot-house conditions. Narrow nutritive ratios are extravagant. 
Protein is the rarest and most costly food element. If one feeder uses a ration with a 
nutritive ratio of 1: 4, and another a ration with a nutritive ratio of 1: 6, the general con- 
ditions and the results in both cases being alike, the inevitable conclusion is that the wider 
ratio furnished, at least, as much protein as the system needed, and that one-third of the 
protein of the narrower ration was used for fuel. It would be no easy matter to find a 
ration compounded with a view to cheapness and the best all round results, and proved 
by long practical tests, which would, when computed, show a nutritive ratio anything 
like as narrow as 1:4, or a potential energy lower than go, except, possibly, in 
extremely hot weather. 
