
‘172 Report oF THE Director oF THE 
| There was during these three periods an average increase of 
161 pounds, or a total of 3134 pounds in the live weight of the 
animals under experiment, and if we assume the estimate of 8.7 
per cent as the amount of fat represented in this gain, it will 
amount to 272.7 pounds, which, added to the fat of the milk, will a 
give 13718.1 pounds as the fat produced by these animals. 
If now we allow the crude fat of the food to contain 17.4 per cent — 
of impurities, there would remain 82.6 per cent, or 16173.2 
pounds of pure fat in the food eaten by these animals, or 
eighteen per cent more fat than was produced by them in their 
milk or increase in weight. This will present a loss of 15.3 per 
cent of the pure fat through lack of digestibility, a loss greater. 
than appears to exist in many experiments made, though H. J. 
Patterson, in a series of digestion experiments with steers, 
reported in Agricultural Science for January, 1892, gives the 
following as the percentage of fat digested in several trials with 
different rations : 

EXPERIMENTS. Food fed in experiments. Per cent fat 
digested. 
TS Aaa ee Stover, corn meal, cotton-seed meal.| 79.12 82 89 
eCOnd y..0./.... 3 Silage, corn meal, cotton-seed meal.| 78.17 84.84 
LNG a ae Silage, corn meals. ei oes. sua ok 14.11" 
PATON soe 0 0'2 Silage, gluten meal, germ feed....| 87.25 84.76 
SUT ean Mane ag RRR SN ta gS hihi IF 81.16 81.72 
BIKE ieee ga oe 
5 Palas ate Metiep ye tate ash abe be Pte thewter she veo ict ay 87.27 USTs 


The average digestibility of fat in the eleven trials was 82.58 
per cent, a result according very closely to those secured in our 
experiments. 
In connection with the very close agreement between the 
amount of fat present in the food and digested by the animal 
and that actually recorded as fat in the milk, which agreement 
would suggest strongly the probable source of the latter, and on 
the other hand the lack of any similiar relation as to quantity 
between the fat produced and the amount of other constituents 
of the food, and especially in view of our present knowledge of 
the physiology of food digestion, it would seem that until strong 
proof shall be submitted that the fat of milk is derived from 


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