This study evaluatedthe effect of ractopamine (RAC) on the performance of finishing pigs and themeat quality of these animals. Seventy crossbred pigs (35 barrows and 35 females)selected for high gain of lean meat, with initial weight of 77.1±0.32kg were distributed in randomized blocks with five treatments (0, 5, 10, 15,and 20 ppm RAC in the diet) and seven replications during 28 days. The experimentalunit was represented by a male and a female pig. Regarding the performance variables,there was a linear increase in final weight with increasing levels of RAC, aswell as in average daily weight gain. An improvement in feed conversion wasobserved for animals fed RAC, and the optimal level - estimated by the LRP model- was ~ 5 ppm. For feed intake, no significant effect on intake of digestiblelysine and energy intake was observed. Carcass yield responses increased linearlywith the RAC dose. Ash content, color component b* and loss drip linearly decreasedwith increasing doses of RAC. There was also a significant difference in thepercentage of ether extract and crude protein in the loin, and treatment with20 ppm RAC showed a lower amount of protein and larger amounts of lipids. Moisturecontent, color component L*, weight loss by cooking and defrosting, shear forceand pH were not affected by the treatment. Concerning the lipid oxidation, therewas no effect of RAC on the concentration of TBARS (thiobarbituric acid reactivesubstances) under cooling and under freezing. Thus, all ractopamine levels improveperformance compared with control and do not negatively affect the quality offresh, chilled or frozen pig meat.
