273.400.  Definitions. — As used in sections 273.400 to 273.405, the following words mean:

  (1)  "Adopter", a person who is legally competent to enter into a contract and who is adopting or buying a dog or cat from a releasing agency;

  (2)  "Adult animal", any dog or cat that has reached the age of one hundred eighty days or six months or more;

  (3)  "Releasing agency", an animal pound, shelter, humane organization, or animal control agency, whether public or private, but not including an individual who occasionally renders humane assistance or shelter in his^* home to a dog or cat;

  (4)  "Sterilization", the surgical removal of the reproductive organs of a dog or cat in order to render the animal unable to reproduce, or the use of an approved serum which will permanently render the animal unable to reproduce.