Orifice insert for a ruminal bolus

Claim 1

An improved controlled release bolus comprising a semipermeable membrane defining a compartment, the compartment being divided into first and second portions by a moveable interface, the first compartment portion containing a swellable osmotic agent, the second compartment portion containing a medicament to be dispensed, a densifier within the second compartment adjacent the membrane and an orifice having an inside cross-section shape and extending through the membrane and the densifier to connect the second compartment portion with the exterior of the bolus, such that when the bolus is in contact with water, the semipermeable membrane allows water to pass therethrough, which water is imbibed by the swellable osmotic agent which forces the interface to move the medicament to be dispensed through the orifice, wherein the improvement comprises an insert which is placed coaxially within the orifice at the point nearest the exterior of the bolus, said insert comprising (1) an insert portion of the same outside cross-section shape as the inside cross-section shape of the orifice and having a grid-like structure extending the length of the insert providing multiple passageways through the insert and the insert portion, and (2) a cap portion integral with the insert portion and of a greater diameter than the insert portion and shaped to allow for attachment means to the area of the bolus surrounding the orifice where the orifice exits the bolus.