Effects of short-term stress, xylazine tranquilization and anesthetization with xylazine plus ketamine on plasma concentrations of cortisol, luteinizing hormone, follicle stimulating hormone and prolactin in ovariectomized pony mares

Long-term ovariectomized pony mares were subjected to one of four treatments: 1) control group — no treatment, 2) stressed group — 5 min of restraint via a twitch, 3) tranquilized group — administered xylazine (1.1 mg i.v. per kg of body weight), and 4) anesthetized group — administered xylazine followed 2 min later by ketamine (2.2 mg i.v. per kg of body weight). Blood samples were taken at −40, −30, −20, −10, −0.5, 10, 20, 30, 40, 50, 60 and 90 min and at 2, 3, 4, 6, 8 and 24 h relative to onset of treatment. Stress increased (P