Evaluation of different doses and durations of ractopamine (Paylean) on growth performance and carcass characteristics of late finishing market pigs

The objective was to evaluate varying doses and durations of ractopamine hydrochloride (RAC; Paylean, Elanco Animal Health, Greenfield, IN) on growth performance and carcass characteristics. Finishing pigs were allotted to 12 treatments 35 d before market. Treatments consisted of negative control [NEG; 13.13% CP, 0.64% standard ileal digestible (SID) Lys] and positive control (POS; 17.77% CP, 0.94% SID Lys); and 2 RAC diets (5 or 7.4 mg/kg) that were fed for the last 7, 14, 21, 28, or 35 d before market. No differences (P > 0.05) were observed between 5 and 7.4 mg/ kg of RAC; therefore, the 2 doses were pooled and compared with the NEG and POS diets. Feeding RAC (pooled average for the RAC groups) increased (P = 0.004) final BW by ~ 3 kg, overall ADG by 12% (P < 0.001), and overall G:F by 14%, but did not affect (P = 0.589) overall ADFI compared with the NEG control. Ractopamine increased (P < 0.05) carcass weight by ~ 2 kg, loin depth by 0.24 cm, and estimated percent lean by 0.64 units, while reducing BF depth by 1.22 mm compared with the NEG diet. Carcass weight, carcass yield, and loin depth increased linearly (P < 0.05) as RAC feeding duration increased, whereas BF depth and estimated carcass lean increased in a quadratic manner (P < 0.05) as RAC feeding duration increased. These data demonstrate that feeding RAC improves growth performance and carcass characteristics compared with the NEG diet. Additionally, the 35-d RAC data illustrate that growth responses observed with RAC feeding programs are not due solely to increased SID Lys levels.