Energia líquida e ractopamina para leitoas em terminação sob altas temperaturas ambientais

The objective of this paper was to assess net energy (NE) levels and ractopamine in the diet of finishing gilts maintained under high temperature environment (29.5 +/- 2.3 degrees C). Forty gilts were used, with initial weight of 69.3 +/- 2.8kg, distributed in a randomized block design, in a factorial scheme 2x4 (0 and 20ppm of ractopamine; and 2,300; 2,424; 2,548 and 2,668kcal/kg NE kg(-1) of feed), and five replications and one animal each. There was interaction (P < 0.05) between NE levels and ractopamine, and the inclusion of 20ppm of ractopamine in the diets containing 2,548 and 2,668kcal reduced (P < 0.05) backfat thickness and increased (P < 0.05) the percentage of lean meat of carcasses. The use of ractopamine improved (P < 0.05) feed gain ratio and increased (P < 0.05) the amount of lean meat in carcasses. It was concluded that ractopamine at a dose of 20ppm provides benefits in performance and carcass traits of gilts under heat stress and this effect is more positive in diets containing higher energy levels (2,548 and 2,668kcal of NE kg(-1)).