The dietary inclusion of feed additives to improve the carcass characteristics of the final product is of great importance for the
pork production chain. The aim of our study was to evaluate the effects of the association of ractopamine (RAC) and conjugated
linoleic acid (CLA) on the performance traits of finishing pigs during the last 26 days prior to slaughter. In total, 810 commercial
hybrid barrows were used. Animals were distributed among treatments according to a randomised block design in a 3 × 3
factorial arrangement, with three RAC levels (0, 5 or 10 ppm) and three CLA levels (0, 0.3 or 0.6%). Pigs fed the diet with 5 ppm
RAC had higher average daily feed intake (ADFI) (2.83 kg; P < 0.05) when compared with those fed 10 ppm RAC and the control
diet (2.75 and 2.74 kg, respectively). Lower ADFI values (P < 0.01) were observed with the diets containing CLA compared with
the control diet with no CLA (2.73 and 2.75 v. 2.85 kg/day, respectively). The average daily weight gain of pigs fed 5 and 10
ppm RAC was þ148 and þ173 g/dayhigher (P < 0.001), respectively, than those fed the control diet. Dietary RAC levels
influenced (P < 0.001) feed conversion ratio (FCR), which was reduced as RAC levels increased, with the pigs fed 10, 5 and 0
ppm RAC presenting FCR values of 2.57, 2.71 and 3.05, respectively. FCR also improved (P < 0.05) with the inclusion of 0.6%
CLA relative to the control diet (2.70 v. 2.84, respectively). There was a significant interaction between CLA × RAC levels
(P < 0.01) for final BW, loin eye area (LEA) (P < 0.05) and backfat thickness (BT) (P < 0.05). The treatments containing 10 ppm
RAC þ 0.6% or 0.3% CLA increased LEA and reduced BT. In conclusion, the level of 10 ppm inclusion of RAC increased the
overall performance parameters of pigs and therefore improved production efficiency. The combined use of RAC and CLA
promoted a lower feed conversion ratio as well as better quantitative carcass traits, as demonstrated by the higher LEA and
lower BT. The dietary inclusion of CLA at 0.3% improved feed efficiency, however, without affecting LEA or BT yields.
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