There were significant differences in the hardness of the varieties of the dent corns fed in these experiments.
Hardness of the corn was determined by a machine designed to find out the crushing resistance of the kernels. In the second and third trials, when three tests were made to determine actual crushing resistance, the means ranged from 24.16 pounds on the Special Reid Yellow Dent or soft corn to 41.46 pounds on the Krug. Average for these two trials showed that it required 27.8 pounds to crush the soft type, 30.3 pounds for the medium, Reid Yellow Dent, and 37.1 pounds to crush the hard type, Krug. The hard type corn was 25 percent harder than the soft type corn and 18 percent harder than the medium.
Culbertson, C. C.; Anderson, Arthur L.; Robinson, Joe L.; and Hammond, W. E.
"Corn of different degrees of hardness for pigs,"
Bulletin: Vol. 33
, Article 1.
Available at: https://lib.dr.iastate.edu/bulletin/vol33/iss375/1