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

• Published in: Journal of animal science Vol. 87; no. 5; pp. 1764 - 1771
• Main Authors: Gonzalez, J.M, Johnson, S.E, Thrift, T.A, Savell, J.D, Ouellette, S.E, Johnson, D.D
• Format: Journal Article
• Language: English
• Published: Champaign, IL American Society of Animal Science 01.05.2009; Am Soc Animal Sci; Oxford University Press
• Subjects: Adrenergic beta-Agonists - pharmacology; Animal productions; Animals; beef cattle; beef quality; Biological and medical sciences; Cattle; Color; Dietary supplements; discoloration; dosage; feed additives; feed supplements; Feeds; finishing; food composition; Food Handling - standards; food retailing; Fundamental and applied biological sciences. Psychology; Humans; immunohistochemistry; Male; Meat - standards; meat aging; muscle fibers; Muscle Fibers, Skeletal - drug effects; Muscular system; myoglobin; myosin heavy chains; nitric oxide; Phenethylamines - pharmacology; protein isoforms; ractopamine-hydrochloride; shelf life; steers; Terrestrial animal productions; Time Factors; vacuum packaging; Vertebrates; Myosin heavy chain; shelf-life; Ractopamine; Bovine; muscle fiber; Fiber; Ox; Shelf life; Vertebrata; Meat animals; Mammalia; Food preservation; Muscle; Artiodactyla; skeletal muscle; Ungulata
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2008-1469

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·animal⁻¹·d⁻¹ of RAC for the final 28 d of feeding. Seventy-two hours postmortem, the long-issimus 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°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.