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. 1 



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 

 in a menu for green goose, with its 36 per cent, or turkey, with 22 

 per cent protein, 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. 



iU. S. Dept. Agr., Farmers' Bui. 142 (1910). 



