Fig. 12-2. Mean contractile dose response of lateral saphenous vein (cranial branch) of cattle in vitro to the selective α-2-adrenergic receptor agonist BHT-920. Cattle were pastured on E- (0%) or E+ (100%) (N. coenophialum) tall fescue for 55 to 85 d (mid March to mid June, 1993, 1994, and 1996). Treatments (E- and E+) were different (P < 0.05). From Oliver et al. (1998).