Effect of standardized ileal digestible lysine and added copper on growth performance, carcass characteristics, and fat quality of finishing pigs.

Two, 120-d, experiments were conducted to determine the effects of standardized ileal digestible (SID) lysine (Lys), added Cu (tribasic copper chloride, Intellibond C; Micronutrients, Inc., Indianapolis, IN), and duration of Cu supplementation on growth performance, carcass characteristics, and fat quality in finishing pigs. In Exp. 1, 1,248 pigs (PIC 337 × 1050; initially 29.0 kg) were allotted to one of six dietary treatments, balanced on average pen weight in a randomized complete-block design with 26 pigs per pen and eight replications per treatment. Treatments were arranged in a 3 × 2 factorial with main effects of SID Lys (85, 92.5, and 100% of the estimated requirement) and added Cu (0 or 150 mg/kg). There were no Cu × SID Lys interactions observed for growth performance or liver Cu concentrations. Increasing SID Lys increased (linear, P < 0.05) ADG, feed efficiency (G:F), final weight, and HCW. Pigs fed 150 mg/kg added Cu had marginally increased (P < 0.10) ADG, G:F, and final weight. Liver Cu concentrations were greater (P = 0.001) in pigs fed added Cu. A marginal Cu × Lys interaction (P = 0.052) was observed for jowl fat iodine value (IV) as increasing SID Lys in pigs fed added Cu increased IV, but decreased IV in pigs not fed added Cu. For Exp. 2, 1,267 pigs (PIC 337 × 1,050; initially 26.4 kg) were allotted to one of eight dietary treatments arranged in a split-plot design. Whole-plot treatments included SID Lys (92.5 or 100% of the estimated requirement) and within each Lys level, there was a 2 × 2 factorial arrangement of treatments with either 0 or 150 mg/kg added Cu and two feeding durations (60 or 120 d). Added Cu did not affect growth performance. Pigs fed 100% of the SID Lys requirement had increased (P < 0.05) ADG, G:F, and final weight compared with those fed 92.5%. A Cu × SID Lys interaction (P < 0.05) was observed for carcass yield and backfat depth. Pigs fed 92.5% SID Lys had increased carcass yield and decreased backfat depth with added Cu; however, pigs fed 100% SID Lys had decreased carcass yield and increased backfat depth with added Cu. Hot carcass weight was increased (P < 0.05) by feeding 100% SID Lys and was marginally (P < 0.10) increased by adding Cu to the diets. In summary, the growth response to added Cu was inconsistent between experiments; however, increasing SID Lys improved growth performance and carcass characteristics.