Interactive Effects of Dietary Ractopamine HCl and L-carnitine on Finishing Pigs: I. Growth Performance

July 10, 2013 — 

A total of 2,152 pigs (C22 � 336 PIC) were used in 4 experiments to determine the interactive effects of dietary L-carnitine and ractopamine HCl (RAC) on finishing pig growth performance. All trials were arranged as factorial arrangements with main effects of L-carnitine (0, 25, or 50 mg/kg in Exp. 1 and 2 and 0 or 50 mg/kg in Exp. 3 and 4) and RAC (0, 5, or 10 mg/kg in Exp. 1 and 0 or 10 mg/kg in Exp. 2, 3, and 4). Dietary carnitine was fed from 38 to 109 kg (Exp. 1 and 3) or for the last 4 or 3 wk before slaughter (118 kg; Exp. 2 and 4, respectively). Ractopamine HCl was fed for 4 wk (Exp. 1, 2, and 3) or 3 wk (Exp. 4) before slaughter. Experiments 1 and 2 were conducted in university research facilities, and Exp. 3 and 4 were conducted in a commercial research facility. All diets were formulated to contain 1.00% total Lys during the last phase of each experiment. In all experiments, pigs fed RAC had increased (P < 0.05) ADG and G:F compared with pigs fed no RAC. Feeding L-carnitine before the RAC feeding period did not affect pig growth performance. In Exp. 1 and 2, L-carnitine did not affect ADG during the last 4 wk; however, in Exp. 2, G:F tended (quadratic; P = 0.07) to improve with increasing L-carnitine. In Exp. 3, L-carnitine � RAC interactions were observed (P < 0.04) for ADG and G:F. Both added L-carnitine and RAC improved performance, but the response was not additive. In Exp. 4, pigs fed L-carnitine had increased (P < 0.04) ADG (0.88 vs. 0.84 kg) and G:F (0.36 vs. 0.35) compared with pigs fed no L-carnitine, and the response was additive to that of RAC. Analysis of treatments common to all experiments showed that pigs fed RAC had increased (P < 0.01) ADG (1.03 vs. 0.93 kg) and G:F (0.40 vs. 0.35) compared with pigs fed no RAC. Pigs fed L-carnitine tended to have increased (P = 0.07) ADG (1.00 vs. 0.96 kg) and improved (P < 0.01) G:F (0.38 vs. 0.37) compared with pigs not fed L-carnitine. These results confirm that RAC improves growth performance of finishing pigs. Added L-carnitine improved growth performance of finishing pigs, and the greatest response was observed in Exp. 3 and 4, which were conducted in commercial research environments. These experiments imply that adding L-carnitine to a finishing diet does not enhance the growth effects of RAC and that effects of RAC and L-carnitine on ADG and G:F are independent.

B. W. James, M. D. Tokach, R. D. Goodband, J. L. Nelssen, S. S. Dritz, K. Q. Owen, J. C. Woodworth and R. C. Sulabo; Interactive Effects of Dietary Ractopamine HCl and L-carnitine on Finishing Pigs: I. Growth Performance; J ANIM SCI July 2013 vol. 91 no. 7 3265-3271 http://www.journalofanimalscience.org/content/91/7/3265.abstract