Differences in lean growth performance of pigs sampled from 1980 and 2005 commercial swine fed 1980 and 2005 representative feeding programs

The objective of this study was to assess how changes in genetics and feeding programs over 25 years in the U.S. commercial swine industry have impacted lean growth performance. Genetic samples (GS) of pigs (n = 162) from the commercial industries in 1980 and 2005 were randomly assigned to 1 of 2 feeding programs (FP) representative of 1980 or 2005. Pigs were placed 3 per pen (n = 54) at approximately 4 weeks of age and were harvested when average BW of the pen exceeded 116 kg. Real-time ultrasound measures for backfat depth and longissimus muscle area at the 10th rib were collected every 4 weeks, beginning at week 8 (group 1) or week 10 (group 2) until harvest. Average daily gain, ADFI, and G:F were calculated for the nursery period (7.0 ± 0.4 to 26.9 ± 0.7 kg BW), finishing period (26.9 ± 0.7 to 119 ± 0.7 kg BW), and overall (7.0 ± 0.4 to 116 ± 0.7 kg BW). Lean ADG and lean G:F were calculated for the period of first real-time ultrasound to harvest (42.7 ± 1.0 kg to 116 kg BW). Pigs from 2005 vs. 1980 GS and pigs fed 2005 vs. 1980 FP reached final BW of 116 kg sooner; 11 and 12 d, respectively. For ADG during finishing and overall, GS × FP interactions were observed, where 1980 GS pigs fed 1980 vs. 2005 FP showed increases of 7.0 and 6.3%, respectively; however, 2005 GS pigs fed 1980 vs. 2005 FP had increases of 12.6 and 12.3%, respectively. Pigs from the 2005 GS had greater ADG during finishing and overall, increased lean ADG, with no difference in ADFI during finishing, overall, and lean gain period or reduced ADFI during nursery which led to greater G:F and lean G:F. Pigs fed 2005 FP had increased ADG during all periods, with reduced ADFI during finishing, overall, and the lean gain test period which led to greater lean G:F and G:F during all portions of the trial. Although via different methods, changes over the past 25 years in the U.S. swine industry with respect to both genetics and feeding programs have resulted in a 15% reduction in days to harvest and a 45% improvement in lean efficiency.