Diet Acceptance and Utilization Responses to Increasing Doses of Thymol in Beef Steers Consuming Forage.

Thymol is an antimicrobial terpene with potential as a feed additive for cattle; however, in vivo data describing the response of forage-fed beef cattle to the increasing provision of thymol is limited. As thymol may affect palatability and exert antimicrobial effects on rumen microbes, defining its effects in vivo is critical to inform adoption. Accordingly, the objectives of this study were to evaluate cattle acceptance of thymol and characterize the effects of increasing thymol doses on diet utilization and ruminal fermentation, with the overarching goal of identifying a maximum tolerable dose for beef cattle. Two 4 × 4 Latin Square experiments were conducted using beef steers consuming forage and providing thymol dosed on alfalfa. Experiment 1 assessed acceptance of thymol at increasing concentrations (0, 110, 220, and 330 mg/kg intake), and experiment 2 assessed diet utilization and fermentation in response to one of four thymol doses: 0, 120, 240, and 480 mg/kg intake. For experiment 1, thymol dose did not affect treatment or forage intake (