. 
af 
; 
; 
FOOD VALUE AND USES OF POULTRY. 23 
is made up of water, protein, and fat, with a very small amount of 
carbohydrates in the form of glycogen, and a small amount of min- 
eral matter, or ash. The nature of these nutrients and the uses to 
which they are put in the body have been discussed in another 
publication.* p 
The differences in composition between different kinds of poultry 
are not very marked. (See fig..1.) There are fully as great differ- 
ences between specimens of the same kind of birds at different ages 
as between different kinds of birds. In general, the younger birds 
contain larger amounts of refuse and water than the older ones and 
have a correspondingly low proportion of actual nutrients. Indi- 
vidual birds of any kind or age may vary greatly in the amount of 
water or fat included in their flesh, and this fact, of course, affects 
their food value as well as their tenderness and flavor. In spite of 
all these differences the following figures may be taken as roughly 
representing the general composition of dressed poultry: The refuse, 
which includes the head, feet, bones, and inedible entrails, makes 
up from 15 to 20 per cent, and the edible portion, including the skin, 
80 to 85 per cent of the weight of the dressed bird. The edible por- 
tion itself consists of 55 to 65 per cent of water, 20 per cent of pro- 
tein, from 10 to 35 per cent of fat, and 1 to 2 per cent of mineral 
matter. 
In spite of their general similarity there are some characteristic 
differences in the composition of different kinds of poultry. The 
light-fleshed birds are richer in protein and poorer in fat than the 
others. In chickens, and probably in all the light-fleshed varieties, 
the young birds yield a larger proportion of protein and a smaller 
proportion of fat than the older ones of the same kind, while in the 
dark-fleshed varieties, such as duck and goose, the young are richer 
- in fat and poorer in protein. 
Some of these differences in composition in the various kinds of 
poultry are great enough to be carefully considered in planning 
dietaries. - If chicken, with its 8 per cent of fat, were substituted 
-m a menu for green goose, with its 36 per cent, or turkey, with 22 
per cent protem, for duckling, with 14 per cent, the proportion of 
building material and fuel furnished to the body might be noticeably 
changed. But too much importance should not be put on the dif- 
ferences between closely related birds, such as chicken, capon, and 
turkey, for they are too slight to affect seriously the nutritive value 
of the diet under ordinary circumstances. Moreover, the greater 
nutritive value which one kind seems to possess may be counter- 
balanced by greater losses in cooking, by leanness or fatness of the 
individual specimen, or by higher price. The consideration of price 
is so important that it will be discussed at length in a later section. 
1U.8. Dept. Agr., Farmers’ Bul. 142 (1910). 
