A needle for delivering a treatment fluid to a target site of an avian bird is provided. Such a needle includes a shaft defining a longitudinal axis and having a proximal end and a distal end. Discrete grooves are defined by the shaft and extend partially along a length thereof. A needle tip extends from the shaft at the distal end thereof. A reservoir assembly includes a body defining first and second holes for receiving the needle therethrough such that the body supports the needle along the length thereof. The reservoir assembly defines a reservoir adapted to receive a treatment fluid through which the grooves pass to carry the treatment substance to the target site. An associated assembly and method are also provided.
