Abstract
Simple SummaryBeta agonists are commonly used in the United States beef industry, offering improved performance in the days leading up to harvest by influencing energy metabolism. Copper has been shown to regulate the biological pathway leading to increased lipid mobilization. However, this connection has not been evaluated in cattle. Therefore, the objective of this study was to determine how Cu influences beta agonist-induced performance, energy metabolism and inflammation in feedlot cattle. Supplementation of Cu resulted in increased liver Cu concentrations, while cattle performance, lipolysis, and some markers of inflammation responded to Cu supplementation differently, depending on whether or not cattle were fed a beta agonist. Therefore, strategic supplementation of Cu may help optimize growth of cattle receiving a beta agonist.Ninety-three Angus-crossbred steers (470 ± 35 kg) were assigned to a 3 × 2 factorial to determine the effects of Cu status and beta agonist (BA) on performance, carcass characteristics, lipolytic rate, and muscle inflammation. Factors included Cu supplementation (mg Cu/kg dry matter (DM)) at: 0 (LO), 10 (MED), or 20 (HI) from Cu amino acid complex (Availa Cu; Zinpro) with no BA (NoRAC) or 300 mg·steer−1·day−1 of ractopamine hydrochloride (RAC; Optaflexx; Elanco) for final 28 days of 88-day trial. Linear and quadratic effects of Cu status within BA treatment were tested. Pre-BA gain was not affected by Cu supplementation (p ≥ 0.57), although day 53 liver Cu quadratically increased (p = 0.01). Average daily gain and muscle IL-8 gene expression quadratically increased (p ≤ 0.01), with MED having greatest gain and gene expression. Ribeye area tended to quadratically increase with Cu supplementation within RAC (p = 0.08). In vitro basal lipolytic rate tended to quadratically increase with Cu supplementation within RAC (p = 0.11), while stimulated lipolytic rate tended to linearly increase within NoRAC (p = 0.10). These data suggest lipolysis and the BA response of steers are influenced by dietary and liver Cu concentrations.
Highlights
Cattle have historically been considered a Cu-tolerant species capable of homeostatic control through hepatic Cu storage and biliary Cu excretion [1]
The objective of this study was to determine if performance, carcass characteristics, and lipolytic rate of beef steers were differentially affected by three distinct liver Cu concentrations achieved through dietary
The body of literature linking trace minerals and growth promoting technologies has been growing over the past decade, signifying the importance of strategic trace mineral supplementation programs in the feedlot
Summary
Cattle have historically been considered a Cu-tolerant species capable of homeostatic control through hepatic Cu storage and biliary Cu excretion [1]. Cu deficiency [2,3] and toxicity [1,4] concerns are still prevalent in both the beef and dairy industry, indicating dietary Cu concentrations should be more carefully evaluated. Cu supplementation strategies for beef cattle rely on the National Academies of Sciences, Engineering, and Medicine (NASEM) [5] recommendation of 10 mg Cu/kg dry matter 4.0/). (DM) developed to prevent Cu deficiency but surveyed consulting nutritionist recommendations vary broadly, from 10 to 40 mg/kg DM of supplemental Cu for finishing cattle [6]. Trace mineral recommendations are interpreted as dietary concentrations required, which are not often analyzed. The current reference range for adequate liver Cu concentration is wide (125 to 600 mg Cu/kg DM) [7], thereby limiting the interpretation of reference ranges to determine optimal Cu supplementation. Copper has been shown to positively influence lipolysis in mouse and cell culture models by hindering phosphodiesterase (PDE) inhibition of cAMP [11]
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