Interactive Effects of Ractopamine and Dietary Fat Source on Performance and Carcass Traits of Finishing Swine

摘要

Crossbred pigs (n = 216) were used to test the interactive effect, if any, of ractopamine (RAC) and dietary fat source on the performance and carcass traits of finishing swine. Pigs were blocked by BW and allotted randomly to pens (six pigs/pen), and,after receiving a common diet devoid of RAC for 1 wk, pens within blocks were assigned randomly to one of four treatments arranged in a 2 x 2 factorial design with 5% fat (beef tallow or soy oil) and RAC (0 or 10 ppm). Individual pig weights and feed disappearance were recorded weekly to calculate ADG, ADFI, and feed-to-gain ratio (F:G). At the conclusion of the 35-d feeding period, pigs were slaughtered at a commercial pork packing plant, and carcass weight, 10th rib fat and longissimus muscle (LM) depths, and fat-free lean yield (FFLY) were recorded prior to chilling. Across the entire feeding trial, ADG was increased (P < 0.001), and F:G was decreased (P < 0.001), by feeding RAC; yet, dietary fat source did not affect (P > 0.10) pig performance. Carcass weight, LM depth, and FFLY were increased (P < 0.002), whereas fat depth was decreased (P < 0.06), in carcasses from RAC-fed pigs. Conversely, carcass composition measures were similar (P > 0.10) between pigs fed tallow or soy oil. Results indicate that feeding 10 ppm RAC will improve the rate and efficiency of gain and carcass leanness; however, dietary fat source had no impact on pig performance or carcass composition.