The study was conducted to evaluate the duration of the supplementation of ractopamine in the diet of finishing gilts maintained under high temperature environment. Forty eight females, with initial weight of 70.4±2.6kg were used. The pigs were distributed in randomized blocks design of six treatments (supplementation of ractopamine for 0, 7, 14, 21, 28 and 35 days pre-slaughter) and four replications, each experimental unit consisted of two animals. The final weight and daily feed intake were not affected (P>0.05) by treatments. The weight gain increased and the feed conversion decreased linearly (P<0.05) according to the increased length of supplementation of ractopamine in the diet. The quantitative characteristics of carcass (weight and hot carcass yield, backfat thickness, percentage of lean meat, depth of muscle and loin eye area) was not influenced (P>0.05) by duration of supplementation of ractopamine in the diet. The weights of the lungs, heart, liver, kidneys and spleen were not modified (P>0.05) by treatments. It was concluded that inclusion of 20ppm of ractopamine in the diet of finishing gilts maintained under high temperature environment during 28 days maximizes the response of daily gain and during 35 days maximizes the response to feed conversion. However, the inclusion of the additive does not alter the quantitative characteristics of carcass and does not affect the development of the viscera.
additives; carcass characteristics; distribution of energy; performance
