Effect of ractopamine-hydrochloride on the fiber type distribution and shelf-life of six muscles of steers

Abstract

The goal of this study was to evaluate the effects of ractopamine-hydrochloride (RAC) supplementation on the myosin heavy chain isoform distribution and shelf-life properties of muscles from beef top round, knuckle, and loin. Thirty-four steer carcasses were selected from 4 separate slaughter groups. Within each slaughter group (3 groups, n = 8; 1 group, n = 10), steers were separated into pens (n = 8) and fed 0 or 200 mg x animal(-1) x d(-1) of RAC for the final 28 d of feeding. Seventy-two hours postmortem, the longissimus lumborum, semimembranosus (SM), adductor, gracilis, vastus lateralis (VL), and rectus femoris were removed from each carcass. A subsample of each muscle was collected for immunohistochemical analysis. Whole muscles were vacuum packaged and wet aged at 1 +/- 2 degrees C for 13 d before processing into steaks for a 5-d simulated retail display study. Daily, steaks were analyzed for reduction of nitric oxide metmyoglobin, lean color, fat color, and surface discoloration. Objective measures of metmyoglobin, oxymyoglobin, L*, a*, and b* values were recorded daily. Ractopamine significantly (P < 0.05) changed the fiber type isoform distribution in all muscles except the SM. The VL and gracilis presented the greatest fiber type switch with approximately 21% of type I fibers switching to type IIA fibers. However, the fiber type shifts induced by RAC supplementation had little to no effect on subjective and objective color measurements during the 5-d retail display period. Metmyoglobin and oxymyoglobin accumulation, L*, a*, and b*-values were not affected (P > 0.05) by RAC supplementation. Percent nitric oxide metmyoglobin reduction data indicate that reducing ability of RAC-treated steaks from the adductor and longissimus lumborum were significantly affected (P < 0.05). Visual panel data suggest that RAC tended (P < 0.10) to have the most detrimental effect on the lean color and surface discoloration scores of steaks from the VL during the last 3 d of display. Ractopamine significantly (P < 0.05) increased the surface discoloration of the rectus femoris and SM on d 5. Although RAC supplementation had no effect on objective color measurements, subjective measurements indicate that it may have some effect on surface discoloration of some muscles.

Effects of Ractopamine Hydrochloride on Growth Performance and Carcass Characteristics in Wool and Hair Lambs

“…The mechanism by which RAC increases longissimus area in our experiment could be interconnected with its ability to alter the metabolic profile of the individual fibres (Gonzalez et al, 2009). In agreement with these researchers, in the current study, RAC supplementation did not affect the colour characteristics in the longissimus.…”

Effect of dietary beta-agonist treatment, vitamin D3 supplementation and electrical stimulation of carcasses on colour and drip loss of steaks from feedlot steers

“…Firstly higher driploss could increase surface moisture resulting in higher reflectance by the aqueous layer as reported by Geesink et al (1993). In addition, the shift towards whiter glycolytic fibre types and hypertrophy of these fibres caused by betaagonisttreatment (Gonzalez et al, 2009, Strydom et al, 2009 and Vestergaard, Henckel, Oksbjerg and Sejrsen, 1994 Wheeler & Koohmaraie, 1997) would have reduced the heme iron pigment concentration and hence result in paler meat (Geesink et al, 1993).…”

“…Firstly higher driploss could increase surface moisture resulting in higher reflectance by the aqueous layer as reported by Geesink et al (1993). In addition, the shift towards whiter glycolytic fibre types and hypertrophy of these fibres caused by betaagonisttreatment (Gonzalez et al, 2009, Strydom et al, 2009 and Vestergaard, Henckel, Oksbjerg and Sejrsen, 1994 Wheeler & Koohmaraie, 1997) would have reduced the heme iron pigment concentration and hence result in paler meat (Geesink et al, 1993).Certain vitaminD 3 treatments reduced the effect of the beta-agonist on lightness for both fresh and aged meat. In fresh samples, 6D7M7N, and to some extent 3D7M were closer to those of the control but still significantly higher (P < 0.05), but in aged meat the effects of both treatments were more pronounced.…”

Effects of ractopamine hydrochloride are not confined to mammalian tissue: Evidence for direct effects of ractopamine hydrochloride supplementation on fermentation by ruminal microorganisms1

“…Ractopamine hydrochloride has a direct effect on individual muscle fibers, causing type-I slowtwitch muscle fibers to transition to type-II fast twitch muscle fibers (Aalhus et al, 1992;Gonzalez et al, 2009). Gonzalez et al (2009) …”

“…The researchers found no other differences in carcass traits measured in experiment 2. Gonzalez et al (2009) evaluated the effect of RAC on shelf-life of steaks from the longissimus lumborum, semimembranosus, adductor, gracilis, vastus lateralis, and rectus femoris after being wet aged at 1 ± 2°C for 13 d. Steaks were evaluated subjectively by a trained panel over a 5-d simulated retail display study and objectively using a Hunter-Lab MiniScan XE. The researchers found that RAC had no effect on objective color measurements (P > 0.05); however, RAC tended to have a detrimental effect on subjective evaluations of lean color and surface discoloration scores of steaks from the vastus lateralis the last 3 d of the display (P < 0.10).…”