Effect of long-term selection for increased leanness on meat and eating quality traits in Duroc swine

A study was conducted to evaluate differences in meat and eating quality traits between purebred Duroc pigs sired by boars currently available and pigs sired by boars from the mid 1980s. Two lines were developed by randomly allocating littermate and half-sib pairs of females to matings by current time period (CTP) or old time period (OTP) boars. Matings by CTP boars were made using fresh semen, and matings by OTP boars were via frozen semen. All available barrows and randomly selected gilts were sent to a commercial abattoir and used for meat and eating quality evaluation. A total of 178 pigs from 23 CTP sires and 99 pigs from 15 OTP sires, across 2 replications and at a mean live weight of 109 kg, were slaughtered and analyzed. Chemical intramuscular fat percentage was determined by lab analysis of a slice from the LM at the 10th rib. Additional meat and eating quality traits measured on the LM were Minolta reflectance and Hunter L color (24 h); pH (24 h and 7 d); water-holding capacity; subjective visual scores for color, marbling, and firmness (48 h); Instron tenderness; cooking loss; and trained sensory panel evaluations (7 d). Time period differences were assessed by use of a mixed model that included fixed effects of sire time period, replication, sex, contemporary group, and the interaction of sex x time period. The random effect of dam and the random effect of sire nested within time period were also included. Loins from pigs sired by OTP boars had greater intramuscular fat (3.48 vs. 3.09%) and visual marbling scores (3.54 vs. 3.07), required less Instron force (5.31 vs. 5.98 kg) to compress, and had darker visual color scores (4.09 vs. 3.87) compared with loins from pigs sired by CTP boars (P < 0.05). No differences were observed between time periods for Minolta reflectance, Hunter L (24 h), water-holding capacity, pH (24 h and 7 d), or subjective firmness scores. Trained sensory evaluations revealed more pork flavor and less off-flavor (P < 0.05) for OTP-sired pigs; however, no differences in tenderness score, juiciness score, chewiness score, or cooking loss were found between lines. Long-term selection response in carcass composition has been at the expense of meat and eating quality traits.