Desempenho, características de carcaça e composição óssea de suínos alimentados com diferentes níveis de ractopamina e fitase

The experiment was carried out aiming at evaluate the effect of using ractopamine and phytase in diets for swines at the end of the finishing period on performance, carcass characteristics and mineral composition on the third metacarpus bone. It was used 240 barrows with initial weight 100.7 +/- 3.9 kg in a random block design, in a 2 x 3 factorial arrangement, with two levels of ractopamine (5 ppm and 10 ppm) and three levels of phytase (0, 500, and 750 FTU) totalizing six diets evaluated in five replications of eight animals per experimental unit. The experiment was conducted for three weeks and, at the end, the animals were slaughtered for carcass evaluation. There was no interaction among the levels of ractopamine and phytase for any of the variables. Body weight, ration daily intake, farm to slaughter shrink, percentage of fat-free lean and contents of ash, phosphorus and fluoride in the bone were not influenced by the diets. The level 10 ppm ractopamine promoted the best results of weight gain, feed conversion, hot carcass weight, total fat-free lean, payment index, and content of calcium in the bone. The evaluated levels of phytase did not influence neither the performance nor the characteristics of the carcass, except the yield, which was higher for the animals fed 500 FTU diet than those that did not receive phytase. Diets 10 ppm ractopamine provided better performance and carcass characteristics than 5-ppm diets. Replacement of inorganic source by phytase (500 or 750 FTU) in the diet does not affect performance, characteristics of carcass neither mineral composition in the bone of swines fed diets with ractopamine.