Effects of exposure to plant-derived odorants on behavior and the concentration of stress-related hormones in steers isolated under a novel environment.

This study was conducted to investigate physiological and behavioral effects of the exposure to plant-derived odorants in Holstein steers (8 month of age) under the acute stress of social isolation in a novel environment. Each steer was tethered in a new room alone and exposed to one of three odorants: a mixture of equal amounts of trans-2-hexenal and cis-3-hexenol (green odor, GO; n = 5), essential oil of grapefruits (EOG; n = 5) and solvent (SOL; n = 6). Behaviors were recorded and blood samples were taken at intervals of 10-15 min for 6 h. Compared with SOL, exposure to GO or EOG decreased the frequency of vocalization (P < 0.05), shortened the latency period before the onset of rumination (P < 0.05) and increased the duration of rumination (P < 0.05). Plasma cortisol concentrations in steers exposed to plant-derived odorants (GO and EOG) during 90-130 min from commencement of sampling were significantly lower (P < 0.05) compared with SOL. These results suggest that appeasing effects of plant-derived odorants on behavioral and physiological stress responses previously reported in laboratory rodents could be also be expected in steers.