Education and Human Sciences, College of (CEHS)


First Advisor

Jessica Lynn Petersen

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Animal Science, Under the Supervision of Professor Jessica Lynn Petersen. Lincoln, Nebraska: August, 2018.

Copyright (c) 2018 Rachel Marie Kubik


β-adrenergic agonists (β-AA), commonly fed to cattle during the last 20-40 days of the finishing period, improve muscle growth by decreasing adipose deposition and increasing muscle accretion. In most cases, final live weights, hot carcass weight and average daily gain have all been shown to increase when β-AA are feed while fed intake, back fat, and marbling all decrease. Two β-AA, Ractopamine HCl (β1-AA) and Zilpaterol HCl (β2-AA) are currently approved for use in beef cattle in the United States. Converse to the beneficial effects of β-AA, heat stress in livestock decreases production efficiency and growth. There have also been reports that β-AA supplementation during times of stress, including heat stress, can cause mobility issues and even death. Little research has been done investigation the interaction between these two factors. The purpose of these studies was to investigate β-AA, heat stress and the interaction between them with respect to transcript expression in different skeletal muscles of cattle and lambs. RNA was isolated from the biceps femoris and longissimus dorsi of cattle supplemented with Ziplaterol and the semitendinosus of lambs supplemented with either Ractopamine or Zilpaterol subjected to either an ambient or heat stressed environment. Two to five million reads per sample was obtained using 3’ QuantSeq and were aligned to either the UMD3.1 bovine transcriptome or the Oar_v4.0 ovine transcriptome. Reads aligned at a rate of 50-60% and represented 10,000 to 13,000 transcripts. No interaction was found between β-AA and heat stress. Between the cattle and sheep studies, β-AA altered cyclic AMP signaling by decreasing proteolysis. Novel mechanisms were also identified relating to exercise and the callipyge phenotype. Heat stress increase the oxidative stress response along with increasing other stress related responses. Based on these results, β-AA do not induce an increased stress risk in livestock species.

Advisor: Jessica L. Petersen