Abstract: A nipple broadly includes a base adapted for coupling to a source of liquid, and an elongated tubular wall presenting a liquid-carrying channel and defining a longitudinal axis. The tubular wall includes a proximate end adjacent to the base and a tip remote from the base. The tip substantially encloses the channel. A liquid passageway is formed through the tip for permitting passage of the liquid from the channel to an animal. A tip ridge is provided on the tip which extends substantially around the passageway. The tip ridge is configured to inhibit the passageway from cracking and growing during usage of the nipple. The base includes an aspiration port for permitting passage of air into the source so that the pressure of the air above the liquid is equalized with the pressure of the air surrounding the source. The aspiration port includes a aspiration slit formed through the base. The aspiration slit is generally normal to a plane defined by the longitudinal axis of the tubular wall and the port.