A quick change adapter and method for use in intravenous treatment of large animals such as cattle, horses, pigs, goats and the like. A method for changing bottles of fluids used in intravenous (IV) fluid therapy, includes the steps of (a) providing an IV set including a funnel having a connection aperture, the funnel being constructed of elastic material; (b) providing an adapter apparatus comprising a cannular portion adapted for sealing mating with the fluid egress aperture of a fluid bottle and a lip portion adapted for sealing mating with the funnel aperture; (c) coupling the interface apparatus in a semi-permanent fashion to the funnel by inserting the lip portion into the funnel connection aperture; (d) inserting the cannular portion into the fluid egress aperture of the fluid bottle; and (e) inverting the fluid bottle to facilitate the flow of fluid. The adapter for connecting an IV Set to a bottle containing fluid, the IV Set of the type having a flexible funnel with a female-type connection aperture, includes a generally cylindrical body with a fluid flow lumen, the body having a lip disposed at one end adapted for male-type connection to the IV Set connection aperture, the opposing end of the body being adapted for male-type insertion into the fluid egress aperture of the bottle.