(a) A medically important antimicrobial drug may not be administered in feed or water to cattle, swine, or poultry unless ordered by a licensed veterinarian through:

(1) A medically important antimicrobial drug prescription; or

(2) A veterinary feed directive.

(b) (1) On or after January 1, 2018, and subject to subsection (c) of this section, a medically important antimicrobial drug may be administered to cattle, swine, or poultry if, in the professional judgment of a licensed veterinarian, the medically important antimicrobial drug is necessary:

(i) To treat a disease or infection;

(ii) To control the spread of a disease or infection; or

(iii) For a surgery or medical procedure.

(2) (i) On or after January 1, 2018, a medically important antimicrobial drug may be administered to cattle, swine, or poultry if, in the professional judgment of a licensed veterinarian, the medically important antimicrobial drug is necessary for prophylaxis to address an elevated risk of contraction of a particular disease or infection.

(ii) Notwithstanding subsection (e) of this section, administration of a medically important antimicrobial drug for the purpose of prophylaxis may not exceed 21 days unless federal label directions require a longer period of use.

(c) Unless administration of a medically important antimicrobial drug is consistent with subsection (b)(1) of this section, a medically important antimicrobial drug may not be administered in a regular pattern to cattle, swine, or poultry.

(d) A medically important antimicrobial drug may not be administered to cattle, swine, or poultry solely for the purpose of:

(1) Promoting weight gain; or

(2) Improving feed efficiency.

(e) (1) Except as provided in paragraphs (2) and (3) of this subsection, a medically important antimicrobial drug may not be administered to cattle, swine, or poultry for a period longer than 21 days.

(2) A medically important antimicrobial drug may be administered to cattle, swine, or poultry for a period longer than 21 days if the federal label directions for the drug require a longer period of use.

(3) (i) A licensed veterinarian may extend administration of a medically important antimicrobial drug for not more than 21 days if, after conducting an on-site visit, the veterinarian determines that the extension is necessary to treat or control the spread of disease or infection.

(ii) A licensed veterinarian may grant additional extensions of not more than 21 days, provided that the veterinarian conducts an on-site visit before each extension.

(f) On or before January 1, 2021, the Department shall adopt regulations prohibiting the routine administration of a medically important antimicrobial drug to dairy cattle entering a dry cycle except when necessary based on an assessment of the presence of an intramammary infection.