SUMMARY
Pigs were fed a control diet, or that diet supplemented with 5 ppm ractopamine for an average of 27 days. Ractopamine improved growth and feed conversion, decreased backfat and improved loin thickness. The economic benefit accruing from the use of ractopamine will depend on market prices, grading grids and the current farm’s carcass quality. Based on our experiment we estimate a “typical” return in the range of $2 to $3 per pig sold.

INTRODUCTION
Paylean® is a feed additive that was recently registered in Canada. The active ingredient of Paylean® is ractopamine, a beta-adrenergic agonist known to stimulate muscle growth and inhibit lipid growth. The final decision to use Paylean® will depend on the relative economics. Similar to other feed additives, there is a cost to using this product. Apart from the cost of the product there are costs associated with the additional nutrients and management required to exploit the performance expected with Paylean®.

MATERIALS AND METHODS
Approximately 530 animals were assigned to receive either a control or a diet supplemented with Paylean® to supply 5 mg/kg ractopamine (RAC). This was to provide an average of 28 days on Paylean® prior to slaughter.
All animals were fed a diet comparable to the barn’s normal gilt finisher, The experiment consisted of two treatments: control or 0.25% Paylean®, equivalent to 5 ppm ractopamine (RAC). Except for total lysine which was increased to 1.00 % and the 5 ppm ractopamine; the Paylean®-fed pigs were fed a diet formulated to the same specification as the controls.

All pigs were shipped to Mitchell’s Gourmet Foods in Saskatoon. Shipping occurred once per week. Pigs were shipped at 116 kg. Market weights were recorded on the morning prior to marketing. The room was completely emptied on week 14 of the growout period (week 6 of the experiment) as per normal barn procedure. Pigs not attaining 116 kg after 14 wk of growout are classified as tail-enders.

Carcass weight, backfat and loin thickness, estimated lean yield, carcass index and carcass loin premiums were recorded at the packing plant according to Mitchell’s standard grid.

Because the economic impact of using ractopamine is dependent on individual farm circumstances, the calculations used different scenarios. We assumed a market price of $1.40 kg and a net market value of $149.00. Other assumptions are described under the appropriate table.

RESULTS and DISCUSSION
Table 1 shows the performance and carcass parameters, which influence the economics of pork production. Additionally, the feed costs, associated with the use of ractopamine are described.

Based on our data, the use of RAC would permit the close-out of a room or barn approximately one week earlier. Assuming that pigs are available to refill that room one week earlier, the net return per pig place would increase by almost $5.00 per year (Table 2). Alternatively, the number of tail-end pigs could be reduced. Reducing the proportion of tail-end pigs from 7.5 % to 0.75 % would increase gross income by about $2.17 per pig sold in a $1.40 /kg market and assuming the tail-end pigs weigh an average of 81 kg, have an average index of 101.9 and receive a loin bonus of $1.86,

If producers are operating under a grading system that does not penalize heavier carcasses, the increase in growth rate could be converted directly into heavier pigs sold (rather than pigs of the same weight sold earlier). Using the growth data obtained from our experiment, and accounting for the additional feed required the return over feed cost would be an additional $3.94 per pig sold (Table 3).

RAC decreased back fat thickness by 1 mm and increased loin thickness by 2.5 mm. In gilts, where backfat was unchanged and loin thickness increased by 2.4 mm, carcass index actually declined by 0.3. In barrows, backfat was reduced by 1.8 mm and loin thickness increased by 2.6 mm, carcass index actually increased by 1.6. Based on the results of our experiment, this increase in carcass index would increase grow income per pig by only $0.80 in a $1.40/kg market.

The increase in loin thickness observed as a consequence of using RAC would increase loin premiums on most farms. However, in our experiment, the control pigs already had a loin thickness of 68.3 mm, and loin premiums dropped from $3.50 to 0.50 when loins exceeded 70 mm.. However, if average loin thickness is 62.8 mm (Mitchell’s Gourmet Foods, personal communication) and assuming a standard deviation of 6.8 mm (PSC Elstow Research Farm, unpublished) RAC would decrease loin premiums from $2.56 to $2.46 (Table 4). A change in loin premiums would dramatically alter this scenario.

CONCLUSION
The actual benefit accruing from the use of RAC will depend on individual farm circumstances. However, based on our data, the “typical” farm will see a return of $2 to $3 per pig sold. Transit losses must be controlled.

ACKNOWLEDGEMENTS
Strategic funding provided by Sask Pork, Alberta Pork, Manitoba Pork Council and Saskatchewan Agriculture and Food Development Fund. Specific funding for this project from Elanco Animal Health is gratefully acknowledged.