Meta-analysis of the relationship between ractopamine and dietary lysine levels on carcass characteristics in pigs

Carcass traits and cutting yields of entire and immunocastrated pigs fed increasing protein levels with and without ractopamine hydrochloride supplementation1–3

“…The data regarding feeding RAC to IC is currently very limited; however, Rikard-Bell et al (2009) found that HCW was increased by feeding RAC to IC and that HCW were greater for IC than both boars and gilts. Although this agrees with Apple et al (2007) and Andretta et al (2012) that feeding RAC can increase the HCW, it cannot be compared with the current study because a step-up in inclusion level of RAC (5 mg/kg for 14 d followed by 10 mg/kg for 17 d) was used by RikardBell et al (2009).…”

“…to 2007 by Andretta et al (2012) showed that feeding RAC increased HCW and an earlier meta-analysis by Apple et al (2007) showed that feeding 10 mg/kg RAC increased HCW by 3.1%. These contradictory results were highlighted by Apple et al (2007) regarding the effect of feeding 10 mg/kg RAC on HCW, with some researchers finding a significant increase (Stites et al, 1991;Herr et al, 2001;Marchant-Forde et al, 2003;Armstrong et al, 2004;Carr et al, 2005a;See et al, 2005), those who found no effect (Watkins et al, 1990;Crome et al, 1996;Stoller et al, 2003;Carr et al, 2005b), and those who found a negative effect (Aalhus et al, 1990;Stoller et al, 2003).…”

“…Backfat thickness is inversely correlated to the duration of RAC supply and level of inclusion as well as the estimated RAC intake (Andretta et al, 2012) and, therefore, it is expected for results to vary between those who found differences in backfat thickness (Watkins et al, 1990;Marchant-Forde et al, 2003;Apple et al, 2004b;Carr et al, 2005b;) and those who did not (Aalhus et al, 1990;Stites et al, 1991;Crome et al, 1996;Herr et al, 2001;Stoller et al, 2003;Carr et al, 2005a;See et al, 2005;Hinson et al, 2011). In light of these findings, the theory that RAC repartitions nutrients away from lipid synthesis to protein accretion does not always appear to hold true.…”

Ractopamine effect on lipid metabolism and GLUT4 amount of finishing pigs

“…This may be a likely explanation for the decrease in fat deposition in the carcass of pigs supplemented with the additive found by several authors (2,12). In fact, Peterla and Scanes (13) found in vitro that adipocytes from pigs treated with RAC showed an increased release of glycerol.…”

“…In addition to acting in important metabolic pathways, RAC is known to be related to lipid and protein metabolism; it has also been shown to have an effect on carbohydrate metabolism of supplemented animals, and thus integrated redirects the nutrients present in the diet favoring the synthesis of proteins at the expense of fat deposition in the carcass (12,21). As with catecholamines, the use of synthetic β-agonists may cause increased concentrations of glucose and nonesterified fatty acids in the plasma of supplemented animals; these changes have already been reported (14,22).…”