RACTOPAMINE (PAYLEAN~(R)) FEEDING PROGRAM EFFECTS GROWTH PERFORMANCE, FEED COST AND CARCASS VALUE

摘要

It has been previously reported (1) that the response to ractopamine (RAC) is not constant but increases, plateaus and then decreases over the course of the feeding period. The reason for this response is not fully understood. Two potential reasons are receptor down regulation and a changing RAC dose (per unit of wt), as the treated pigs grow heavier while consuming the same amount of feed. If either of these reasons is true, then it may be possible to maintain the RAC response for a longer period of time by changing the RAC dose throughout the feeding period. Therefore, the objective of this study was to determine if changing the levels of RAC in the diet during different phases of feeding could enhance the RAC response.