Mass. Gen. Laws ch. 140 § 151B
A veterinarian registered under section 55 or 56A of chapter 112 who renders emergency care or treatment to, or who euthanizes, a dog or cat that is injured on any way shall receive payment from the owner of such dog or cat, if known, or, if not known, from the city or town in which the injury occurred in an amount not to exceed $250 for such care, treatment or euthanization; provided, however, such emergency care, treatment or euthanization shall be rendered for the purpose of maintaining life, stabilizing the animal or alleviating suffering until the owner or keeper of the dog or cat is identified or for 24 hours, whichever is sooner. A veterinarian who renders such emergency care or treatment to a dog or cat or euthanizes a dog or cat shall notify the municipal animal control officer and the animal control officer shall assume control of the dog or cat or the remains of the dog or cat.
Mass. Gen. Laws ch. 140, § 151B