California Code, Business and Professions Code - BPC § 12731

(a) Notwithstanding any other provisions of this code, where livestock is sold on the basis of weight at a public sales yard, or by or at any livestock market, market agency, or dealer which is subject to the Packers and Stockyards Act of 1921 (7 U.S.C. Sec. 181 et seq.), the livestock shall be weighed by a weighmaster, and a weighmaster certificate shall be issued to the buyer and seller.

(b) The term “livestock” includes cattle, sheep, swine, horses, mules, and goats.