Idaho Code § 25-2116
During the breeding season every user of the public range shall place upon the range used by him a registered bull of beef breed not less than fifteen (15) months of age nor more than eight (8) years of age for every twenty-five (25) head or fraction thereof of female breeding cattle pastured by him on such range, and no person shall permit any bull to run on the same range at any other time than during three (3) successive breeding seasons: provided, the term "female breeding cattle" shall not apply to female cattle under twelve (12) months of age: provided, that any two (2) or more persons may join together in furnishing such bull when the aggregate number of female breeding cattle turned loose upon the same range by any such two (2) or more persons does not exceed the number of twenty-five (25) head; provided further, that the owner or owners of female dairy cattle may pasture them on the public range without a bull, as above provided, if such female dairy cattle are taken up each night to be milked and the owner or owners keep for the breeding of every fifty (50) head of such cattle a registered bull of dairy breed, but no person shall allow a bull of dairy breed to run at large.
Any person or persons violating any of the foregoing provisions shall be guilty of a misdemeanor and on conviction thereof shall be fined not less than twenty-five dollars ($25.00) and not exceeding $100.
Idaho Code § 25-2116