Effects of ractopamine step-up use programs on finishing pigs fed under commercial conditions

Abstract

Objectives: To provide live performance and carcass information on ractopamine (RAC) use programs in commercial field conditions and to compare a feeding regimen in which the dietary concentration of RAC was increased after 2 or 3 weeks with a regimen in which the dietary RAC concentration was constant for 35 days. Methods: A total of 1050 pigs were assigned to pens (n = 48) on the basis of weight and gender. Average body weight at trial initiation was 78.5 kg. Four dietary treatments were randomly assigned to pens and stratified across weight and gender. Dietary treatments included control (0 g/tonne RAC for 35 days); constant (5.0 g/tonne RAC for 35 days); Step 2 (5.0 g/tonne RAC for 14 days then 10.0 g/tonne for 21 days); Step 3 (5.0 g/tonne RAC for 21 days then 10.0 g/tonne for 14 days). Pen and feed weights were recorded weekly to determine live performance variables. All pigs were transported to market after the experimental period, and packer sheet data were collected for assessment of carcass response. Results: Average daily gain, feed efficiency, and carcass parameters were better in pigs fed diets supplemented with RAC. Live performance and carcass measures were better in pigs on Step 2 and Step 3 programs, and these pigs produced more carcass lean than pigs on the constant RAC program. Implications: Under commercial management conditions, live performance and carcass measures were better in pigs fed RAC for 35 days, and further benefits were obtained with RAC step-up programs.