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ARS Home » Plains Area » Lubbock, Texas » Cropping Systems Research Laboratory » Livestock Issues Research » Research » Publications at this Location » Publication #339990
Title: Zilpaterol hydrochloride affects cellular muscle metabolism and lipid components of ten different muscles in feedlot heifers

Author
item HERGENREDER, JERILYN - Kemin Industries, Inc
item LEGAKO, JERRAD - Texas Tech University
item DINH, THU - Mississippi State University
item Broadway, Paul
item SPIVEY, KARI - Texas Tech University
item BAGGERMAN, JESSICA - Texas Tech University
item HUTCHESON, JOHN - Merck Animal Health
item JOHNSON, BRAD - Texas Tech University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Growth promotants such as beta-agonists are extremely valuable to beef producers and enhance the growth and performance of finishing cattle. These compounds fed before harvest have been reported to increase lean carcass tissue by stimulating protein accretion while simultaneously decreasing fat synthesis. While these products have been extensively researched and proven effective, much is still unknown about the effects of beta-agonists on muslce and fat metabolism. Therefore the purpose of this study was to examine muscle metabolism and fatty acid profiles of 10 muscles from the carcasses of heifers either supplemented with the beta-agonist zilpaterol hydrochloride (ZH). Supplementation altered myosin isoform RNA expression and also altered the proportions of myosin isoforms (muscle fiber types). Muscle fiber cross-sectional area was increased by ZH. Lipid saturation was effected by treatment and muscle type; however, ZH did not effect triglyceride content. Overall, this study demonstrates that ZH supplementation can alter the muscle biology and metabolism of muscle cells in at least 10 different muscles in a beef carcass that contribute to lean tissue deposition and protein accretion in the carcass. This information is valuable to producers, feedlot operators, and others who feed cattle for harvest and further solidifies previous research reporting the positive benefits of ZH on growth, performance, and profitability.

Technical Abstract: This study determined if zilpaterol hydrochloride (ZH) altered muscle metabolism and lipid components of ten muscles. Crossbred heifers were either supplemented with ZH (n = 9) or not (Control; n = 10). Muscle tissue was collected (adductor femoris, biceps femoris, gluteus medius, infraspinatus, latissimus dorsi, longissimus dorsi, pectoralis profundi, semitendinosus, subscapularis, trapezius) at harvest. The mRNA abundance of AMPka, IGF-I, MHC-I, IIA and IIX, ß1-adrenergic receptor (ßAR) and ß2AR was determined. As well as, cross-sectional area and proportion of myosin isoforms, ß1AR, ß2AR, ß3AR, nuclei, and satellite cell density. Furthermore, neutral and polar lipid (NL and PL) fatty acids (FA) were quantified (mg/g). Zilpaterol hydrochloride decreased MHC-IIA mRNA (P = 0.007). In addition, ZH decreased total nuclei and ß1AR and increased MHC-IIX cross-sectional area (P = 0.021). Muscle affected AMPka, IGF-I, MHC-I, IIA, IIX, and ß1AR mRNA concentration (P = 0.037). Furthermore, muscle affected fiber type proportion, fiber cross-sectional area, and the densities of nuclei, ß1AR, ß2AR, ß3AR, and satellite cells (P = 0.030). Quantity of NL FA were not affected by ZH (P = 0.173). However, among PL FA the ratio of PUFA:SFA was greater with ZH (P = 0.048). Total NL FA were affected by muscle (P = 0.046). Meanwhile, total PL FA did not differ due to muscle (P = 0.242). However, prominent PL FA,18:0, 18:1 trans, and 18:2 n-6 were each greater (P < 0.05) among the oxidative subscapularis compared with glycolytic semitendinosus and adductor femoris. Overall, these data reveal that ZH impacts muscle metabolism and myogenic activity that establishes protein deposition. Meanwhile, ZH did not alter triglyceride content (NL), but cell membrane saturation (PL) was influenced, in accordance with alterations to muscle fiber type. Muscle also influenced muscle fiber type and lipid components. Therefore, muscle biology is greatly influenced by muscle but also through dietary inclusion of ZH.