BACKFAT THICKNESS AND CARCASS WEIGHT AS PREDICTORS OF THE YIELD OF HAMS AND LOINS OF PIG CARCASSES

Detailed cut-out data were obtained from 930 hog carcasses comprising a two-way sampling structure of nine fat categories and 11 weight categories. Fat categories covered a range of 38 to 127 mm in total backfat (sum of maximum shoulder and maximum loin fat) and weight categories covered the range of 57 to 82 kg in warm carcass weight. Carcass weight had virtually no effect on percent yield of ham and/or loin, whereas total backfat had a large and linear effect. The linear effect of fat was consistent for each weight class and for each level of trim. Yield, based on weight of boned-defatted loin and ham expressed as a percent of warm carcass weight, increased by 0.02% for each kg increase in carcass weight and decreased by 0.96% for each 1-cm increase in total backfat.Approximately 97% of the commercial hogs graded in Canada are likely to have a total backfat thickness within the range of 56 to 109 mm. The relationships between total backfat and percent yield documented in this cut-out study indicate that this variation in backfat would be associated with a range of approximately 5% in yield of boned-defatted ham and loin. This is approximately four times the yield differential observed between the averages of grades A and B. Implications in respect of commercial grade standards are discussed.