Hogs are usually sold in the United States on a liveweight basis. Official federal grade standards for hogs were not established until 1952.
The purpose of this study was to attempt to develop objective carcass grade specifications for slaughter barrows and gilts. These grade specifications should have economic significance and at the same time should be practical and acceptable to the hog industry.
Detailed carcass measurements were made of 600 hog carcasses at the Iowa Packing Company, Des Moines, Iowa. Each carcass then was subjected to a detailed cutout test to determine the weight and quality g:t:ade of the various component wholesale cuts and trimmings. The ratio of the weights of the four high-value lean cuts (hams, loins, picnics and boston butts) to the total carcass weight was computed for each carcass. This ratio (called the index of lean) is a measure of the relative values of the hog carcasses. The higher the index of lean, the higher the value of the carcass, until the point is reached where the carcasses are discounted for lack of quality. Thus, for any schedule of prices for the various wholesale cuts and trimmings there is an optimum index of lean which will yield the highest carcass value.
Brough, Owen L. and Shepherd, Geoffrey
"Objective grade specifications for slaughter barrow and gilt carcasses,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 32
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol32/iss421/1