THE EFFECT OF SLAUGHTER WEIGHT ON THE CARCASS CHARACTERISTICS OF YORKSHIRE BARROWS AND GILTS

Thirty-two Yorkshire pigs, 16 barrows and 16 gilts, were slaughtered at four weights (85, 92, 103 and 112 kg) to determine the effect of slaughter weight on selected carcass characteristics. The left side was divided into shoulder, loin, ham and belly for which untrimmed and trimmed weights were recorded. The effect of the new Canadian grading regulations (1978) on the index values of carcasses was determined. Fat at the shoulder (point of maximum thickness) and at the loin (point of maximum thickness) increased (P < 0.01) with slaughter weight. The response of fat thickness to the increase in slaughter weight was linear (P < 0.01) at the shoulder but non-linear at the loin. Carcasses of the 103-kg slaughter weight group had higher index value under the new regulations while in the other slaughter groups, only minor changes in the index value were observed. Dressing percentage was not affected by slaughter weight or by sex. Heavier carcasses yielded heavier trimmed and untrimmed cuts (P < 0.01). The response was linear. No influence of sex was observed. The quantity of trimmings required to meet the specifications of the retail trade also increased in a linear fashion with slaughter weight (P < 0.01) but was not influenced by sex. The weights of the four untrimmed cuts as a percent of chilled left side remained unchanged throughout the period studied. Similarly, percentages of trimmed ham, loin and shoulder were constant: 18.34, 21.00 and 21.93% of the chilled left side, respectively. Fat thickness at the loin was a relatively good predictor of percent trimmed cuts while the fat measurement at the shoulder was found to be an unreliable predictor.