Evaluation of Different Ractopamine Feeding Programmes

According to a paper by W. Ying and colleagues1 presented at the 2011 Kansas Swine Day, Ractopamine HCl (RAC; Paylean; Elanco Animal Health, Greenfield, US) has been widely used to improve growth and carcass characteristics of late–finishing pigs in the US.

The maximal growth responses to feeding RAC occur during the initial feeding period but these responses decline over time. The cause of the reduced performance to RAC over time is thought to be down-regulation of beta receptors. Although different RAC feeding strategies have been studied, data are not consistent on the ideal approach between a constant or step-up feeding method. With the application of automatic feeding systems, pigs can be fed following a curve, slowly increasing the RAC dosage through time. For their experiment, the researchers hypothesised that gradually increasing RAC dosage on a daily basis may provide for an improved growth and economic return compared to constant or step-up feeding.

The researchers found that feeding RAC improved performance but that the feeding programme had few effects on carcass weights or measurements.

Ying and colleagues used a total of 934 barrows and gilts (PIC 337 × 1050, initially 240lb) were used in a 26-day experiment to evaluate the effect of different RAC feeding programmes on growth and carcass traits of finishing pigs.

Treatments included a basal diet with (1) no RAC for 26 days (control), (2) 7.5ppm RAC for 26 days (constant), (3) 5ppm RAC for days 0 to 14 and 10ppm for days 14 to 26 (step-up) and (4) RAC concentration increased daily from 5ppm on day 0 to 10ppm on day 26 using the FEEDPro (Feedlogic Corp., Willmar, MN) system (curve).

Each treatment had 10 pens with a similar number of barrows and gilts in each pen.

From days 0 to 14, pigs fed diets containing RAC had greater (P<0.001) average daily gain and better (P<0.001) feed to gain ratio than those fed the control diet. Pigs fed the constant or step-up RAC feeding methods had greater (P<0.04) average daily feed intake than those fed the control diet.

From days 14 to 26, all RAC–fed pigs had greater (P<0.001) average daily gain and better (P<0.001) feed to gain ratio than control pigs.

Overall, pigs fed diets containing RAC had improved (P<0.001) average daily gain and better feed to gain ratio than pigs fed the control diet. Pigs fed the step-up RAC programme had greater (P=0.01) average daily gain and better (P=0.02) feed to gain ratio than the constant RAC programme.

Pigs marketed on days 14 and 26 had heavier (P<0.001) hot carcass weights when fed diets containing RAC compared with control pigs. Pigs fed constant RAC had greater (P=0.002) carcass yield than control pigs. Pigs fed the constant RAC programme also had greater (P=0.03) loin depth on day 14 than control pigs. No differences were found in carcass traits among RAC treatments.

Ying and colleagues concluded that feeding RAC improved performance regardless of feeding method but few differences were observed between the RAC feeding programmes in carcass weights or measurements.

Effects of Diet Mix Time on Finishing Pigs Fed Ractopamine

A quite low inclusion rate of only 4.5 to 9g per ton of Ractopamine HCl (RAC; Paylean) for the last 45 to 90lb of gain is recommended by the manufacturer, Elanco Animal Health. For maximum performance in pigs consuming diets with RAC, much attention is given to dietary factors such as increasing the concentration of protein and amino acids but a factor that has not been addressed is the importance of mixing time for diets with RAC, according to C.B. Paulk and colleagues2 at Kansas State University in the introduction to their paper presented at the University’s 2011 Swine Day.

With the objective to determine the effects of dietary mix uniformity on the response to RAC in finishing pigs, they conducted two experiments to determine the effects of mix uniformity for diets with RAC when fed to finishing pigs.

From their results, the Kansas group concluded that increasing feed mixing time from 0 to 360 seconds had no significant effects on pig performance.

In Experiment 1, they used a total of 200 pigs (PIC TR4 × 1050; average bodyweight of 198.4lb) in a 33–day growth assay arranged in a randomised complete–block design with five pigs per pen and eight pens per treatment. Treatments were a corn-soybean meal-based control diet mixed for 360 seconds and the mixed control diet with 9g per ton of RAC added before additional mixing for 0, 30, 120 and 360 seconds. The experiment was designed to determine the effects of nutrient utilisation from a thoroughly mixed diet with a potential non–uniform distribution of RAC.

Pigs fed diets with RAC had improved (P<0.05) average daily gain, feed to gain ratio, final bodyweight, hot carcass weight, dressing percentage, backfat thickness, loin depth and percentage carcass lean compared with control pigs. Increasing mix time from 0 to 360 seconds decreased the coefficient of variation for chromium (Cr) from 67 to 12 per cent but had no effect on the response to RAC for any growth or carcass measurement.

In Experiment 2, a total of 160 pigs (PIC TR4 × 1050; average bodyweight of 205lb) were used in a 27–day growth assay arranged in a completely randomised design with two pigs per pen and 16 pens per treatment.

Treatments were a corn-soybean meal-based control mixed for 360 seconds and control diets with 9g per ton RAC mixed for 0, 30, 120 and 360 seconds. Thus, this experiment was designed to determine the combined effects of potentially non–uniform distribution of both nutrients and RAC.

The use of RAC increased (P<0.01) average daily gain, feed to gain ratio, final bodyweight, hot carcass weight, dressing percentage, percentage lean and loin depth.

Increasing mix times from 0 to 360 seconds decreased the coefficient of variation for salt from 51 to 12 per cent with no significant effect on average daily gain, feed to gain ratio, hot carcass weight, dressing percentage, backfat thickness, loin depth or percentage lean.

Paulk and colleagues concluded that increasing mix time of diets from 0 to 360 seconds did not significantly affect the response of finishing pigs to RAC, but in Experiment 2, a mixing time of 120 seconds for the complete diet and RAC (CV of 15 per cent) resulted in the numerically lowest (quadratic; P<0.15) feed to gain ratio.

Effects of Dietary Astaxanthin and Ractopamine on the Growth and Carcass Characteristics of Finishing Pigs and the Colour of Chops

In the introduction to their paper at Kansas Swine Day, J.R. Bergstrom and colleagues3 explain that astaxanthin is a carotenoid without potential for vitamin A activity in mammals that exists naturally in various plants, algae, and seafood. Although used primarily for the pigmentation of farm salmon and trout, its unique molecular structure makes it a potent antioxidant but there is little information on the effects of dietary astaxanthin on pig performance and fresh pork colour and quality.

Furthermore, they say, the effects of Ractopamine HCl (RAC) and gender on the colour shelf-life of fresh pork have not been clarified and so the Kansas group conducted an experiment to determine the effects of feeding various levels of astaxanthin (AX, from Xanthophyllomyces dendrorhous yeast), either with or without RAC, on growth and carcass characteristics of finishing pigs and colour shelf-life characteristics of longissimus muscle (LM) chops from barrows and gilts during simulated retail display.

The researchers found that, although there were no differences in the colour of fresh LM chops to indicate any consumer preferences initially, the colour shelf–life was improved during retail display for chops from pigs fed RAC for the last 26 days of finishing. Also, LM chops from gilts had improved colour shelf-life compared with chops from barrows. Color shelf-life was not significantly influenced by the addition of dietary astaxanthin in this study.

They used a total of 160 pigs (initially 198lb), which were weighed and randomly allotted to one of eight dietary treatments fed for approximately 26 days pre–harvest.

Dietary treatments consisted of a corn-soybean meal-based control diet, the control diet with 7.5, 15, 30, 60, or 120ppm AX, and a corn-soybean meal-based diet with 10ppm RAC and 7.5 or 20ppm AX. Each treatment had 10 pens, with two pigs (one barrow and one gilt) in each pen. A split-plot design with repeated measures was used to compare colour characteristics of LM chops from individual barrows and gilts.

Overall, pigs fed RAC had increased (P<0.01) average daily gain and final bodyweight and improved feed to gain ratio compared with pigs not fed RAC.

Among pigs not fed RAC, feed to gain ratio improved (quadratic; P<0.05) and a trend (quadratic; P<0.06) was observed for increased average daily gain with increasing AX to 60ppm.

For carcass characteristics, pigs fed RAC had greater (P<0.03) hot carcass weight, 10th–rib LM area, 24–hour LM pH and fat–free lean index (FFLI) than those not fed RAC treatments.

Among pigs not fed RAC, a trend (quadratic; P<0.07) occurred for increased yield with increasing AX.

During six days of retail display, the initial (day 0) NPPC colour score of LM chops from gilts was greater (P<0.03) than that of chops from barrows.

Subjective discoloration scores of LM chops did not differ initially, but increased (linear; P<0.01) daily and were greater (P<0.02) on day 6 for chops from barrows and pigs not fed RAC than chops from gilts and pigs fed RAC, respectively (gender × day and treatment × day interactions; P<0.04).

The CIE a* (redness) and CIE b* (yellowness) of LM chops decreased (linear; P<0.01) during retail display, and chops from gilts and pigs fed RAC had lower (P<0.04) CIE b* than chops from barrows and pigs not fed RAC, respectively, especially on day 0 (gender × day and treatment × day interaction; P"0.01).

Overall (days 0 to 6), concluded Bergstrom and colleagues, discoloration scores and changes in objective total colour were lower (P<0.02) for LM chops from gilts and pigs fed RAC. These observations suggest that colour shelf–life was extended for chops from gilts and pigs fed RAC.

References

1 Ying W., J.M. DeRouchey, M.D. Tokach, S.S. Dritz, R.D. Goodband and J.L. Nelssen 2011. Evaluation of Ractopamine HCl feeding programs on growth performance and carcass characteristics of finishing pigs. Proceedings of Kansas Swine Day 2011, p266-271.

2 Paulk C.B., L.J. McKinney, J.D. Hancock, S.M. Williams, S. Issa and T.L. Gugle. 2011. Effects of diet mix time on growth performance of finishing pigs fed Ractopamine HCl. Proceedings of Kansas Swine Day 2011, p272-277.

3 Bergstrom J.R., G.R. Skaar, J.L. Nelssen, T.A. Houser, M.D. Tokach, R.D. Goodband, J.M. DeRouchey and S.S. Dritz. 2011. Effects of dietary Astaxanthin and Ractopamine HCl on the growth and carcass characteristics of finishing pigs and the color shelf-life of longissimus chops from barrows and gilts. Proceedings of Kansas Swine Day 2011, p330-340.

Further Reading You can view the full papers in the proceedings of the 2011 Kansas Swine Day by clicking here.

June 2012