Okla. Stat. tit. 2, § 2-6-189: Nighttime inspections

The Board shall cause an examination and inspection of all

cattle, bison, sheep, swine, goats, horses, mules, and other

equines, and the food products thereof, slaughtered and prepared in

the establishments hereinbefore described for the purposes of

intrastate commerce to be made during the nighttime as well as

during the daytime when the slaughtering of said cattle, bison,

sheep, swine, goats, horses, mules, and other equines, or the

preparation of said food products, is conducted during the

nighttime.