Three experiments investigating the use of the non-antibiotic growth promoter, ractopamine hydrochloride (trade name: Paylean), were reported at the Kansas Swine Day conference last year and are summarised here by senior editor, Jackie Linden.
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 bet ween 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 un iformity 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...
Source: Argentine Beef Packers S.A.
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