Inspectors and duly authorized agents of the state, city, county, and city and county health departments shall have free access at all hours of operation to premises where animals are slaughtered, or horsemeat or other meat products are processed, prepared, packed for pet food, or offered for sale or sold, for purposes of inspection. If slaughtering or carcass preparation or processing of meats and meat products is conducted at hours considered overtime for state employees, or on legal holidays, the owner or operator of the establishment shall by contract or agreement with the department, make arrangement to defray the additional cost for salaries and expenses for persons employed by the department to conduct the necessary inspection work during the overtime periods.