A meta-analysis was carried to evaluate the relationship of ractopamine with nutritional variables and performance in pigs. The database included 29 articles published in national and international journals from 1990 to 2007, totaling 155 treatments and 3,786 pigs. The average inclusion of ractopamine was 15.3ppm (ranged from 0 to 30ppm) and the daily average intake of ractopamine was 24.9mg (ranging from 0 to 84mg). Inclusion of ractopamine in diets showed (P<0.05) a positive correlation with weight gain (0.214) and feed efficiency (0.231). Ractopamine did not change (P>0.05) the feed intake, but increased (P<0.05) in 12% the feed efficiency, in 10% the weight gain and in 3.7% the final body weight. The concentrations of protein, lysine and energy in diets affected the animal response feeding with ractopamine. Increasing a unit in dietary lysine concentration resulted in increase of 341g in weight gain (ADG=0.687+0.341LIS, R²=0.71) and 1.3% in feeding efficiency (EF=2.14+1.34LIS; R²=0.62). Ractopamine improves pig performance, however, the interaction between additive and nutritional components must be considered in diets formulation.
agonists; lysine; metabolism; ß-adrenergics
