PSX-B-18 - Behavioral and Physiological Responses of Ewes in Hardwood Silvopastures vs. Open Pastures

Managing livestock in silvopasture systems can help reduce heat stress and improve animal behavior and productivity. However, quantifying physiological benefits for animals in pastoral systems is challenging because the sampling procedures require animal handling; this is stressful and elevates plasma cortisol, a stress hormone. Hair cortisol (HC) is a relatively non-invasive and reliable measure of chronic stress, but it has received limited use especially in pasture systems. We compared behavioral and physiological (temperature, hair and blood cortisol) responses of ewes that grazed mid-stage hardwood silvopastures vs. open pastures. The study site consists of 0.27-ha black walnut (Juglans nigra; BW) and honeylocust (Gleditsia triacanthos; HL) silvopastures and open pasture (OP) treatments, each replicated three times. Thirty-six Katahdin ewes were assigned to one of the treatments for a 6-week summer grazing trial. Ewe weights and intravaginal temperatures were recorded routinely; trail cameras captured animal behavior. Blood was collected via jugular venipuncture; hair grown during the trial was collected from the loin region. Blood and hair cortisol concentration was determined by ELISA. Body weight gains and plasma cortisol levels did not differ among treatments. Ewes on OP had higher HC on Day-21 and Day-42 (P ≤ 0.007) and 0.5-1.0 °C hotter (P ≤ 0.04) intravaginal temperatures between 1200h-1700h than ewes on silvopasture treatments. Overall, ewes on OP spent more (P < 0.001) time loafing and less (P < 0.10) time lying down compared to ewes on silvopasture treatments. Trees within the silvopastures moderated ambient conditions, both reducing stress and improving the behavioral and physiological responses of ewes.