EFFECTS OF RACTOPAMINE (PAYLEAN) DOSE AND FEEDING DURATION ON PIG PERFORMANCE IN A COMMERCIAL FINISHING FACILITY

A total of 1,035 gilts were used in a 28day trial conducted in a commercial research facility to determine the influence of ractopamine (Paylean) dose (4.5 or 9.0 g/ton) and feeding duration (7, 14, 21, or 28 days prior to slaughter) on pig performance and carcass composition. Ractopamine supplementation at 4.5 g/ton for 14 to 28 days, and 9 g/ton for 7 to 28 days, improved (P<0.05) ADG by 26 to 35% (0.35 0.46 lb/d) and F/G by 16 to 20% (0.64 to 0.79) during the 28-days prior to slaughter. Due to these improvements in growth, carcass weights increased 8 to 10 pounds over controls. Fat depth and lean percentage improved (linear, P<0.01) with increased feeding duration. Ractopamine dose did not affect carcass lean parameters. However, carcass yield improved (P< 005) when ractopamine was fed at 9.0 g/ton. Feed cost per pound of gain increased (P<0.01) with increasing feeding duration for Paylean and was greater (P<0.05) for pigs fed the 9.0 g/ton dose for 28 days as compared to the control. However, feeding ractopamine at 4.5 g/ton for 14 to 28 days and 9 g/ton for 7 to 28 days improved income over feed costs by $3.53 to $ 4.76 per head compared to pigs fed the control diet. Return over feed costs improved due to the increased carcass weights and improved feed efficiency with the greatest values achieved with a 14 to 21 day feeding duration. These data indicate feeding ractopamine at either 4.5 or 9.0 g/ton for 14 to 21 days prior to slaughter is a cost-effective strategy to optimize return while minimizing increases in feed cost per pound of gain.


Summary
A total of 1,035 gilts were used in a 28day trial conducted in a commercial research facility to determine the influence of ractopamine (Paylean TM ) dose (4.5 or 9.0 g/ton) and feeding duration (7, 14, 21, or 28 days prior to slaughter) on pig performance and carcass composition.Ractopamine supplementation at 4.5 g/ton for 14 to 28 days, and 9 g/ton for 7 to 28 days, improved (P<0.05) ADG by 26 to 35% (0.35 -0.46 lb/d) and F/G by 16 to 20% (0.64 to 0.79) during the 28-days prior to slaughter.Due to these improvements in growth, carcass weights increased 8 to 10 pounds over controls.Fat depth and lean percentage improved (linear, P<0.01) with increased feeding duration.Ractopamine dose did not affect carcass lean parameters.However, carcass yield improved (P< 005) when ractopamine was fed at 9.0 g/ton.Feed cost per pound of gain increased (P<0.01) with increasing feeding duration for Paylean and was greater (P<0.05) for pigs fed the 9.0 g/ton dose for 28 days as compared to the control.However, feeding ractopamine at 4.5 g/ton for 14 to 28 days and 9 g/ton for 7 to 28 days improved income over feed costs by $3.53 to $ 4.76 per head compared to pigs fed the control diet.Return over feed costs improved due to the increased carcass weights and improved feed efficiency with the greatest values achieved with a 14 to 21 day feeding duration.These data indicate feeding ractopamine at either 4.5 or 9.0 g/ton for 14 to 21 days prior to slaughter is a cost-effective strategy to optimize return while minimizing increases in feed cost per pound of gain.

Introduction
Ractopamine is a feed additive that improves growth rate, feed conversion, and lean deposition.Due to the dietary costs associated with feeding ractopamine, determining a dose and feeding duration that provides optimum return and minimizes increases in feed cost per pound of gain is essential.The objective of this evaluation was to determine the effects of ractopamine dose (4.5 or 9.0 g/ton) and feeding duration (7, 14, 21, or 28 days prior to slaughter) on pig performance and the associated economic implications.

Procedures
This experiment was completed in a commercial finishing research facility.Forty-five pens of gilts (PIC 337 × C22, 227.5 ±1.4 lb) were allotted to treatment 28 days prior to slaughter.Treatments included pigs fed 4.5 or 9.0 g/ton ractopamine for 7, 14, 21, or 28 days prior to slaughter, and a control treatment without ractopamine.Diets were corn-soybean meal-based, formulated to contain 0.75 and 1.00 % total dietary lysine for the control and ractopamine supplemented diets, respectively.Feed delivery was recorded daily, and feed remaining was determined weekly when pen weight gain was measured.Pens had totally slatted floors, were 10 × 18 ft, with 23 pigs per pen.Each pen was equipped with a 50inch dry feeder (Staco) and cup waterer.The facility was a double curtain sided finishing barn with a deep pit.At the conclusion of the feeding period, each pen was identified with a unique tattoo to obtain pen carcass composition and revenue information.At slaughter, fat and loin depth were measured with an optical probe and used to calculate lean percentage.Fat, loin depth, and lean percentage were adjusted to a common carcass weight for statistical evaluation.An economic evaluation was completed using actual feed costs and carcass revenue information attained from the pens in this evaluation.Data were analyzed using pair-wise orthogonal contrasts between each of the nine treatments, as well as for the main effects of ractopamine dose and duration.Pen was the experimental unit in all data analyses.
Income over marginal feed costs increased due to improved carcass weights and feed efficiency.Feed costs per pound of gain were only increased (P>0.05) over controls in pigs fed 9.0g/ton ractopamine for 28 days prior to slaughter.However, feed cost per pound of gain increased (linear, P<0.03) with feeding duration.These data indicate that feeding ractopamine at either 4.5 or 9.0 g/ton for 14 to 21 days prior to slaughter is a cost-effective strategy to optimize return while minimizing increases in feed cost per pound of gain.It should be understood that feeding ractopamine offers the most economic opportunity for producers who are limited in grow-finish space and are having difficulty in optimizing carcass weights.However, the shorter feeding durations fed in this study indicate feed cost per pound of gain is not affected by ractopamine supplementation due to the improvements in feed efficiency.Therefore, the shorter feeding durations are a more conservative economic approach for operations not constrained in finishing capacity.Operations with excess finishing capacity typically have a more conservative value for improvements in ADG, as finishing spaces are available to otherwise attain desired market weights.Understanding the biologic and economic dynamics of feeding ractopamine helps producers develop operationally dependant strategies concerning the cost-effective use of ractopamine.a A total of 45 pens ( 23 pigs/pen, 5 pens/treatment) of gilts were fed 4.5 or 9.0 g/ton ractopamine (Paylean TM ) for 7, 14, 21, or 28 days prior to slaughter, along with a control treatment without ractopamine.b,c,d,e Means in the same row without a common superscript differ (P<0.05).
f Yield was calculated using live carcass pen-weights attained at the slaughter plant.
g Backfat, loin depth, and percent lean were adjusted to a common carcass weight.