The effect of copper supplementation on performance and carcass characteristics of cattle utilizing growth promoting technologies
Growth promoting technologies such as beta agonists and hormone implants are used extensively throughout the feedlot industry (Samuelson et al., 2016). These technologies are known to improve performance and efficiency of growth and thus are vital to sustained profitability for cattle producers. The ability to further improve the effectiveness of these technologies would improve productivity of cattle and may be accomplished through the strategic supplementation of trace minerals such as Cu. Although industry recommendations for Cu are two times NASEM (2016) recommendations, little research has evaluated trace mineral supplementation in addition to growth promoting technologies. Therefore, the effects of greater concentrations of minerals such as Cu in the diet of cattle utilizing growth promoting technologies has not yet been validated. The research trials described in this thesis were designed to 1) determine the effect of Cu status of finishing beef steers on beta agonist induced growth performance and 2) examine the impacts of industry rates of Cu supplementation on the implant growth response of finishing feedlot steers. Through our first research objective, the supplementation of varying concentrations of Cu to finishing feedlot cattle differentially impacted the beta agonist induced performance response of cattle. Within cattle receiving the beta agonist treatment, performance was greatest at Cu supplementation at NASEM (2016) recommendations. These performance differences were observed in Cu supplemented cattle with adequate liver Cu status suggesting further classification of Cu status for optimal growth is needed. Through our second study performance was impacted by an interaction between implant and Cu in which cattle not supplemented with Cu experienced a 24.7% increase in ADG due to implant while industry recommendations of Cu supplementation resulted in a 15.3% improvement in ADG due to implant. Additionally, liver Cu concentrations tended to increase and liver Mn concentrations decreased 14 days after implantation, while liver Zn and plasma Zn revealed trends for decreases due to implant. Together these studies indicate Cu may impact the physiological response to growth promoting technologies and that implants may alter mineral metabolism. Additionally, these data revealed that supplementation of Cu beyond NASEM (2016) recommendations may not promote optimal performance from cattle utilizing growth promoting technologies. Collectively, the studies presented in this thesis find that concentrations of Cu commonly supplemented within the industry are not merited. This work warrants additional research to better understand the role of Cu in growth induced through technologies such as beta agonists and hormone implants.