Oregon Revised Statutes Animals § 607.261

(1) No person shall turn upon, or allow to run upon, the open range, any bull other than a purebred bull of a recognized beef breed. The State Department of Agriculture shall by regulation define “purebred bull of a recognized beef breed.” No person shall turn upon, or allow to run upon, the open range, any female breeding cattle unless the person turns with such female breeding cattle one purebred bull of a recognized beef breed for every 25 females or fraction thereof of 10 or over.

(2) No owner of any stallion or jackass, of the age of 18 months or more, shall permit it to run upon the open range during the period April 1 to October 31 of each year. No owner of any ram shall permit it to run at large upon the open range during the period July 1 to October 31 of each year.