The Effects of Long Term Selection for Reduced Backfat and Increased Loin Muscle Area on Meat and Eating Quality Traits in Duroc Swine

A study was conducted to evaluate differences in performance, carcass composition, and eating quality characteristics of pigs sired by purebred Duroc boars currently available and pigs sired by purebred Duroc boars from the mid 1980’s. Two lines were developed by splitting and randomly allocating littermate and 1⁄2 sib pairs of females to matings by current (CTP) or old (OTP) time period boars. Subsequent boar, barrow, and gilt progeny from two replications were weighed on test at a group mean live weight of 140 lbs. Off-test ultrasonic LMA, BF10, and IMF measurements were collected on 789 pigs at a mean live weight of 240 lb. Records on pigs sired by CTP boars, from both replications (n=556), represented 23 sires while pigs sired by OTP boars (n=231) consisted of 15 sire groups. All available barrows and randomly selected gilts (n=277) were sent to a commercial abattoir and measurements of tenth-rib backfat (CBF10), last rib backfat (CLRBF), last lumbar backfat (CLLBF), and loin muscle area (CLMA) were collected. Chemical intramuscular fat percentage was determined by lab analysis of a loin sample from the 10th rib face of the longissimus muscle. Additional meat and eating quality traits measured were: Minolta reflectance and Hunter L (24 and 48 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). Six serial ultrasonic measurements of 10th rib loin muscle area (LMA), off-midline backfat (BF10), and intramuscular fat percentage (IMF) from the first replication were collected every two weeks and used to assess deposition rate and growth pattern differences. There was no significant difference in average daily gain of pigs sired by boars from the two time periods. Pigs sired by CTP boars had larger (P < 0.05) LMA measurements and less BF10, while pigs sired by OTP had significantly more IMF. Carcass evaluation revealed larger CLMA measurements, and significantly less CBF10, CLRBF, and CLLBF measurements for pigs sired by CTP boars. Pigs sired by OTP boars had a higher intramuscular fat percentage, lower Instron tenderness values, and higher subjective marbling and color scores than pigs sired by CTP boars (P < 0.05). There were no significant differences between time periods for Minolta reflectance, Hunter L (24 and 48 h), water holding capacity, pH (24 h and 7 d), and subjective firmness scores. Trained sensory evaluations revealed higher (P < 0.05) flavor scores and lower off-flavor scores for OTP sired pigs; however, no significant differences in tenderness score, juiciness score, chewiness score, and cooking loss were found between lines. Progeny of OTP boars began the test period at heavier weights and begin to decrease in daily body weight gain toward the conclusion of the test period, finishing with no advantage in body weight when compared to progeny of CTP boars. The analysis of serial backfat measurements revealed a linear pattern of backfat deposition between 150 and 270 lbs. Pigs sired by OTP boars deposited more backfat (P Disciplines Animal Sciences | Genetics | Meat Science Comments This is a proceeding published as Schwab, C. R., T. J. Baas, D. W. Newcom, and K. J. Stalder. The effects of long term selection for reduced backfat and increased loin muscle area on meat and eating quality traits in Duroc This conference proceeding is available at Iowa State University Digital Repository: https://lib.dr.iastate.edu/ans_conf/15 swine. 29th Proc. National Swine Imprv. Fed. Conf. Ann. Mtg. Ames, IA. Dec. 9-10. 2004, pp. 37-46. Posted with permission. This conference proceeding is available at Iowa State University Digital Repository: https://lib.dr.iastate.edu/ans_conf/15 The Effects of Long Term Selection for Reduced Backfat and Increased Loin Muscle Area on Meat and Eating Quality Traits in Duroc Swine C. R. Schwab, T. J. Baas, D. W. Newcom, and K. J. Stalder Department of Animal Science, Iowa State University, Ames, 50010