POULTRY-CRAFT. It 
It is said that an excess of carbohydrates pours through the system undigested. 
That supposition is contrary to the known effects of feeding heavily of carbon- 
aceous matter. The immediate consequence of feeding fat to excess is scour- 
ing. Some authorities on feeding say all the protein taken into the system is 
used: 7, e. —an excess of protein is impossible. But this is not in accordance 
with practical experience in feeding ‘‘ narrow” or highly nitrogenous rations. 
Experience teaches that such rations cause digestive troubles as surely, if not 
as quickly, as an excess of fats. 
152. Food Values.— There are two standards of measurements of food 
values: 
(1). The measurement of quality, of proportionate value of principal ele- 
ments :— NuTRITIVE Ratio. 
(2). The measure of bulk, of content, of degree of concentration, of total 
heating capacity : — PoTENTIAL ENERGY. 
The Nutritive Ratio of a food (single article or mixture) is the ratio of 
its proteids to its carbohydrates and fats, reduced to terms of carbohydrates ; — 
one part of fat by weight having a fuel value two and one-half times as great 
as an equal weight of carbohydrates. The chemical analysis of a food being 
known, the nutritive ratio is determined thus, taking corn as the example: 
Corn (see table, 4153) contains 10.4 parts protein, 70.3 parts carbohydrates, 
5 parts fat: its nutritive ratio is: z 
10.4: 70.3+(5%2.5) = 1: 7.9. 
The PorentiaL EneErGy of a food is the gross fuel value of its digestible 
matter. It is expressed in calorées per ounce. A calory is the amount of 
heat required to raise one gram of water one degree centigrade. One ounce 
of carbohydrates or protein has a potential energy of one hundred and sixteen - 
calories. One ounce of fat has a potential energy of two hundred and sixty- 
four calories. The potential energy of any food substance of which the 
chemical composition is known is calculated thus, taking corn again as the 
example, and using the figures in the table as percentages of an ounce: 
(264 X .05)+(.703+.104) 116 = 106. 
The nutritive ratio and potential energy of each single article may, when 
computing values of compound foods, or of rations, be regarded as constant 
quantities. Asa matter of fact, they vary greatly in different samples of the 
same article, but calculations from the figures in the table, which are averages 
of a large number of analyses, may properly be assumed to give the average 
and usual values of the different foods. 
The values of a ration vary with its ingredients, and are calculated from 
averages of the values of the ingredients. (See 158). 
