ARS | Publication request: The effects of R-salbutamol on growth, carcass measures and health of finishing pigs

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 18, 2012
Publication Date: November 1, 2012
Citation: Marchant Forde, J.N., Lay Jr, D.C., Marchant-Forde, R.M., Mcmunn, K.A., Richert, B.T. 2012. The effects of R-salbutamol on growth, carcass measures and health of finishing pigs. Journal of Animal Science. 90:1-9.

Interpretive Summary: In order to maximize production efficieny, swine in the U.S. are often fed a physiologically-active compound (the beta-agonist ractopamine) that alters the animal's metabolism over the 4 weeks immediately prior to slaughter. The compound results in decreased fat and increased lean muscle, increasing the farmer's profit. However, there are also concerns that ractopamine affects the animal's well-being, making them harder to handle, hyperactive and more aggressive. It may be that other beta-agonists can produce the same production results, without the negative side-effects. We tested one such product - salbutamol, which is often used to treat humans for asthma. We previously demonstrated that salbutamol did not have negative well-being effects when fed to finishing pigs. The aim of this study was to see whether it conferred similar positive production effects to those seen with ractopamine. When we fed pigs either 2, 4 or 8 parts per million of salbutamol, we did see that they gained more weight, yet ate less feed than pigs fed a control diet, thereby being more efficient at converting the feed to weight gain. Salbutamol-fed pigs also increased loin muscle size and decreased backfat depths compared to control pigs. Some measures of meat quality however, showed a trend in the opposite direction - that is, control-fed pigs had better color and intra-muscular fat marbling scores, although we did not carry out any detailed sensory measures of meat quality to determine if the consumer could detect a difference. The type and magnitude of all the treatment differences in our study were similar to those seen in many other studies with ractopamine. Therefore, we can conclude that salbutamol may be useful as an alternative beta-agonist compound to be fed to pigs, which will confer production benefits for the producer, although further research will be necessary.

Technical Abstract: A pure form of salbutamol has the potential to deliver positive production benefits to the swine industry. The aim of this experiment was to determine the effects of salbutamol on growth, carcass measures and health of finishing pigs. The study used 192 pigs (88.8 ± 0.9 kg BW) housed in groups of 6 in 32 pens and assigned to 1 of 4 treatments: 1) control (CTL) – 0 mg/kg salbutamol, 2) 2R – control diet with 2 mg/kg of the pure R-enantiomer of salbutamol, 3) 4R – control diet with 4 mg/kg of pure R-salbutamol, or 4) 8RS – control diet with 8 mg/kg of a 50:50 mixture of the R- and S- enantiomers. All diets were offered ad libitum for 4 wk. All pigs were weighed and pen feed intakes recorded weekly. At slaughter, individual hot carcass weights (HCW) and measurements of the 10th rib loin muscle area (LMA), color, marbling, firmness, and backfat, last lumbar and midline backfat depths were collected. Data were analyzed using Proc GLM of SAS, with pen as the experimental unit. Overall, 2R and 4R pigs had greater ADG than CTL pigs (P < 0.05) and at slaughter, were heavier than CTL pigs (P < 0.01). Overall, 8RS pigs had lower ADFI (P < 0.05) and CTL pigs had poorer G:F (P < 0.001) than the other three treatments respectively. All salbutamol fed pigs had 5-6 kg greater HCW (P < 0.001), 2-3% increased carcass yield (P < 0.001), 5.6 cm2 larger LMA (P < 0.01), 3-4 mm less 10th rib backfat (P < 0.01) and 2 mm less last lumbar backfat (P < 0.05) than CTL pigs. However, control pigs had higher loin muscle color scores (P < 0.05) and marbling scores (P < 0.001) than all salbutamol-treated pigs. Taken together, these data indicate that salbutamol altered protein metabolism, and as little as 2 mg/kg R-salbutamol has a positive effect on pig growth and carcass composition. However, the effects of salbutamol on meat quality require further research.