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IOWA ACADEMY OP SCIENCE 
decrease from the 300th to the 355th day being plain. To eat 
the certain minimum amount of protein, which may be assumed 
as absolutely necessary and to be as shown in Plate XLII, the 
pigs must narrow the ration toward the finish (after the 255th 
day) in order to get protein sufficient. The quality of the ration 
must be changed so as to have more protein in a hundred pounds 
of feed, inasmuch as less units of feed are being eaten because of 
an evident lack of consumptive ability. 
Just what would lessen the capacity of the animals after the 
193d day is not definitely known but this may be attributed to : 
1. A lack of alimentary volume due to the greatly increased 
stores of internal fat. 
2. An actual lessening in the demands for feed nutrients 
because the most rapid period of growth has been passed. The 
milch cow when giving a large quantity of milk daily will eat 
more feed than if not lactating; the same is true of the sow 
suckling pigs. The working man eats more heartily, naturally, 
than the sedentary one ; the growing child eats to the limit oft- 
times compared to the mature and aged. It is thus seen that the 
pig which is rapidly growing has great demands upon its di- 
gestive apparatus to eat and digest feed to furnish the neces- 
sary nutrients for assimilation. The greater the outlet for the 
assimilable nutrients the greater, ordinarily, the consumptive 
ability of the animal in question. 
One dominant reason for the sometimes ineffective results 
secured in feeding according to ordinary standards is the diffi- 
culty of knowing the resultant of the many, specific units, as 
many as a hundred, which in all probability are comprised in 
an ordinary feeding-stuff such as maize grain, or meat meal, or 
oats, or oil-extracted fiax grain residue. The suitability of dif- 
ferent individual feeds for the animals in question has been de- 
termined largely from a careful observation of results secured in 
practical Animal Husbandry. This general knowledge of practi- 
cal feeding-stuffs and their effects is of great advantage in 
supplementing the best feeding standards. At best the ‘‘best” 
standard available today is but a crude approximation of actual 
requirements. When the appetite is given full control of what 
shall be eaten it is surprising to note how the pigs naturally 
select the specific feeds which swine herdsmen have long since 
approved as of the best, and what is equally surprising the pigs 
show marked avoidance of those feeds usually considered as ill- 
adapted to swine. 
