Young Scholar Presentation: Metabolic Modifiers in Beef Cattle: Current Application and Future Considerations

In the upcoming years, the expansion of global animal agriculture will be forced to keep pace with expected world population growth. Feeding the growing world will be accomplished by producing more food with fewer resources and improving efficiency in the methods in which food is currently being produced. This leaves great opportunity for the scientific community to improve efficiency in food and agricultural sciences. Metabolic modifiers can be used in livestock production to increase live efficiency and improve yields of animal-derived food products. Less is known about other benefits associated with the use of metabolic modifiers in beef cattle production. Multiple projects in our laboratory have focused on the use of metabolic modifier products in beef cattle, specifically ractopamine hydrochloride (RAC). Key outcomes of this research include production advantages in rate of gain, feed efficiency, and improvements in carcass yields in cattle fed RAC. The objectives of this research were to use commercially relevant approaches to answer applied research questions. Studies were conducted to analyze the effects of feeding cattle RAC with or without supplemental zinc and chromium and feeding cattle RAC with or without the ionophore monensin and the antibiotic tylosin phosphate. Rate of gain (9-16%), and feed efficiency (8-16%) during the finishing period were increased (P < 0.01) in cattle fed RAC compared with cattle not fed RAC. Carcass characteristics impacting quality and yield grade were minimally affected in cattle fed RAC compared with cattle not fed RAC. There were no differences (P > 0.05) in live animal performance or carcass traits with feeding supplemental zinc and chromium to cattle fed RAC. There were no differences (P > 0.05) in live animal performance or carcass traits when including or removing monensin and tylosin from the finishing diet of cattle fed RAC. In addition, research was dedicated to the effect of RAC on glucose and lipid metabolism parameters. Glucose and insulin were measured in non-fasted cattle. Glucose and insulin were measured after glucose-tolerance tests were conducted in cattle fed RAC (300 mg ractopamine·animal^-1·d^-1 for 21 days) in two studies. Only in one study were baseline and glucose-induced insulin levels reduced (P < 0.01) in cattle fed RAC compared with cattle not fed RAC. Overall, this research provided a brief sampling of strategies and possible considerations to be used with RAC in the beef cattle industry.