6 BULLETIN" 507, U. S. DEPARTMENT OF AGRICULTURE. 
Summary of digestion experiments with chicken fat in a simple mixed diet. 
Experi- 
ment No. 
Subject. 
Protein. 
Fat. 
Carbohy- 
drates. 
Ash. 
274 
275 
H. F. B 
D. G. G 
Per cent. 
61.7 
65.9 
75.3 
65.3 
62.7 
76^0 
69.4 
Per cent. 
92.9 
93.8 
94.6 
92.0 
92.3 
93.9 
95.3 
92.2 
Per cent. 
96.1 
96.4 
98.0 
97.0 
96.0 
97.0 
97.5 
97.4 
Per cent. 
62.3 
276 
277 
290 
291 
292 
293 
R.L. S 
O.E.S 
H. F. B 
D. G. G 
R. L. S 
O.E.S 
76.1 
64.1 
57.9 
57.3 
71.7 
67.3 
68.3 
93.4 96.9 
65.7 
The average coefficient of digestibility of the total fat eaten during 
these tests was 93.4 per cent. As the ether extract of the feces, how- 
ever, is known to contain metabolic product and undigested fat from 
the basal ration, which though nearly so was not absolutely fat free, 
a correction has been applied in the case of this fat and the others 
studied to determine the average digestibility of total fat consumed. 
Digestion experiments with the basal ration as the only source of fat 
have been reported in connection with the earlier animal fat experi- 
ments, from which it was concluded that 9.89 per cent of the total 
weight of water-free feces is made up of metabolic products and undi- 
gested fat from the food, 1 which latter must have been an insignifi- 
cant quantity, since the total amount in the diet was so small. 
Subtracting the quantity represented by this percentage from the 
total ether extract of the feces, a value is obtained more nearly repre- 
senting the weight of unutilized fat. The corrected value for the 
digestibility of fat then becomes 96.7 per cent. 
GOOSE FAT. 
In the United States goose fat is used as such only to a very limited 
extent and chiefly among those of foreign birth or parentage who 
adhere to special food customs. 
Owing to the impossibility of obtaining goose fat in quantity from 
local dealers, an unusually fat or " stall-fed" goose was purchased. 
It weighed 27.5 pounds, 13 pounds of fat being obtained when the fat 
was cut away from the flesh and rendered in the usual way. The 
goose fat, which at room temperature (about 20° C.) is a soft, pale- 
yellow, granular solid, tended to separate into two layers on stand- 
ing — an upper, oily layer, and a lower, more or less solid layer. By 
using freshly rendered fat, rancidity was avoided, which is likely to 
occur on keeping, perhaps owing to the 0.7 to 3.5 per cent of soluble 
fatty acid which the fat contains. 
As regards previous work with this fat, Arnschink 2 conducted an 
experiment of four days' duration with a dog weighing 8 kilograms, 
in which an average of 50 grams, containing 70 per cent of oleic 
i U. S. Dept. Agr. Bui. 310 (1915), p. 20. 
" Ztschr. Biol., 8 (1890), pp. 443, 444. 
