The Crossroads between Zinc and Steroidal Implant-Induced Growth of Beef Cattle

SIMPLE SUMMARY: This review addresses the physiological and biochemical connections between steroidal implants and Zn and their interaction to influence growth in beef cattle. Steroidal implants have been widely accepted as a growth-promoting technology that provides an unmatched economic return to the producer and improves beef production’s environmental sustainability. Likewise, decades of research have indicated Zn is vital for skeletal muscle growth. Considering Zn is an essential trace mineral, strategic Zn supplementation to implanted cattle may optimize beef production. Although many interrelationships between steroidal implants and Zn are new and forthcoming, the literature reviewed hereafter indicates roles for Zn in a multitude of growth processes pertinent to steroidal implant-induced growth and uncover changes in Zn metabolism due to steroidal implant use. ABSTRACT: Growth-promoting technologies such as steroidal implants have been utilized in the beef industry for over 60 years and remain an indispensable tool for improving economic returns through consistently improved average daily gain via increased skeletal muscle hypertrophy. Zinc has been implicated in skeletal muscle growth through protein synthesis, satellite cell function, and many other growth processes. Therefore, the objective of this review was to present the available literature linking Zn to steroidal implant-induced protein synthesis and other metabolic processes. Herein, steroidal implants and their mode of action, the biological importance of Zn, and several connections between steroidal implants and Zn related to growth processes are discussed. These include the influence of Zn on hormone receptor signaling, circulating insulin-like growth factor-1 concentrations, glucose metabolism, protein synthesis via mTOR, and satellite cell proliferation and differentiation. Supplemental Zn has also been implicated in improved growth rates of cattle utilizing growth-promoting technologies, and steroidal implants appear to alter liver and circulating Zn concentrations. Therefore, this review provides evidence of the role of Zn in steroidal implant-induced growth yet reveals gaps in the current knowledge base related to optimizing Zn supplementation strategies to best capture growth performance improvements offered through steroidal implants.