Ractopamine HCl improved cardiac hypertrophy but not poor growth, metabolic inefficiency, or greater white blood cells associated with heat stress in concentrate-fed lambs

Authors

Rebecca M. Swanson, University of Nebraska - LincolnFollow
Kristin A. Beede, University of Nebraska - LincolnFollow
Micayla D. Freeman, University of Nebraska - Lincoln
Morgan L. Eggleston, University of Nebraska - Lincoln
Ty B. Schmidt, University of Nebraska-LincolnFollow
Jessica L. Petersen, University of Nebraska - LincolnFollow
Dustin T. Yates, University of Nebraska - LincolnFollow

ORCID IDs

Jessica L. Petersen

Date of this Version

2019

Citation

Transl. Anim. Sci. 2019.3:1786–1791

Comments

© The Author(s) 2019.

Open access

doi: 10.1093/tas/txz098

Abstract

Heat stress decreases livestock performance and well-being (Hahn, 1999; Nienaber and Hahn, 2007), causes metabolic dysfunction that decreases growth efficiency (O’Brien et al., 2010), and alters cardiovascular function (Crandall et al., 2008). Each year, heat stress costs the livestock industry up to $2.5 billion (St-Pierre et al., 2003). Ractopamine HCl acts as a nutrient repartitioning agent (Beermann, 2002); classified as a β adrenergic agonist (βAA), it shares pharmacological properties with adrenaline (Beermann, 2002). βAA increase muscle mass and decreases fat deposition through unknown mechanisms (Beermann, 2002). In feedlot cattle, they increase growth efficiency and improve carcass yield and merit (Scramlin et al., 2010; Buntyn et al., 2017), which increases profit and allows more meat to be produced from fewer animals. However, because βAA act via a stress system, it is unclear how the products affect animals under stress conditions. β1AA and β2AA can also cause tachycardia, heart palpitations, and arrhythmias (Sears, 2002). We hypothesize that β1AA combined with heat stress may overstimulate the adrenergic system, resulting is metabolic dysfunction and decreased performance. Sheep are a common model for cattle, and thus, the objective of this study was to determine the impact of ractopamine HCl on health and cardiovascular parameters, growth, and metabolic efficiency in feeder lambs.