390 
IOWA ACADEMY OF SCIENCE 
same in the diet with any large degree . of satisfaction. It 
wonld seem that it is well to allow common salt to pigs just 
^s average humans like to take it, namely, — ad libitum accord- 
ing to appetite. 
THE FREE-CHOICE SYSTEM OF SWINE FEEDING. 
To determine whether or not pigs have the ability to balance 
their own rations preliminary investigations have been made 
in the laboratories of the Animal Husbandry Section, Iowa 
Experiment Station. 
Three groups of five pigs each were fed in dry lot practically 
from weaning time, July 7, 1914, until they were more than 
eight months of age. One of these groups (II) was continued 
until almost a year old, or until April 14, 1915. Lot I was fed 
from separate self-feeders these specific feeds : whole corn grain, 
meat meal (containing 60 per cent of protein), whole oats, char- 
coal (made from maple wood), limestone (finely ground and 
running very high in calcium carbonate), salt (common rock) 
and water (from the ordinary College wells). Lot II was fed 
practically the same, the only difference being that linseed oil 
meal was added to the list of feeds. Lot III was fed differently 
from Lot I in that both oil meal and wheat middlings were 
idded in separate compartments. All lots had free-choice, there- 
fore, as to what they should eat and as to how much they should 
drink. Every pig was a ‘‘law unto itself” and progress was 
made in the experiment on the basis of “free and equal oppor- 
tunity” for each individual in every lot concerned. 
One lot only, namely. Lot II, which is entirely representative, 
is presented in so far as the feeding record is concerned (the 
charcoal, limestone, salt, and water figures are not included in 
this paper) . Plate XLI shows the corn, meat meal, oats, and oil 
meal eaten daily, on the basis of ten day periods, throughout the 
experimental life of that group, or from the time they were 83 
days of age until they were almost a year or exactly 350 days. 
Evidently the palatability of the various feeds changed con- 
siderably (consult Plate XLI) as the feeding period progressed; 
*in the beginning these pigs ate a ration composed practically of 
less than 80 per cent corn. The percentage of the different feeds 
eaten is given for the representative 3d, 10th, 18th, and 25th 
periods, or when the animals were respectively 108, 178, 258 
and 328 days of age respectively. 
