Simple SummaryRodeos often include a calf roping event, where calves are first lassoed by a rider on a horse, who then dismounts, ties the calves’ legs, lifts it from the ground and releases it back to the floor. We tested whether calves that were familiar to the roping experience stress during the roping event, and found increased concentrations of stress hormones in their blood after the roping. We also found increased concentrations of stress hormones in the blood of calves that had never been roped before but were just marshelled across the arena by the horse and rider. We conclude that the roping event in rodeos is stressful for both experienced and naïve calves. AbstractRodeos are public events at which stockpeople face tests of their ability to manage cattle and horses, some of which relate directly to rangeland cattle husbandry. One of these is calf roping, in which a calf released from a chute is pursued by a horse and rider, who lassoes, lifts and drops the calf to the ground and finally ties it around the legs. Measurements were made of behavior and stress responses of ten rodeo-naïve calves marshalled by a horse and rider, and ten rodeo-experienced calves that were roped. Naïve calves marshalled by a horse and rider traversed the arena slowly, whereas rodeo-experienced calves ran rapidly until roped. Each activity was repeated once after two hours. Blood samples taken before and after each activity demonstrated increased cortisol, epinephrine and nor-epinephrine in both groups. However, there was no evidence of a continued increase in stress hormones in either group by the start of the repeated activity, suggesting that the elevated stress hormones were not a response to a prolonged effect of the initial blood sampling. It is concluded that both the marshalling of calves naïve to the roping chute by stockpeople and the roping and dropping of experienced calves are stressful in a simulated rodeo calf roping event.