The present invention relates to a method and device suitable for storing and transporting animal semen, and more particularly to a method and disposable device for storing and transporting equine semen.
A device for transporting equine and other animal semen was introduced to the equine breeding market in 1984 with the trade name xe2x80x9cThe Equitainerxe2x80x9d (at least a partial description of which can be found in U.S. Pat. No. 4,530,816). Since that time, horse breeding by artificial insemination using transported chilled semen has become dominant in the equine breeding sector. The technique of slowly cooling the sample en route to its destination has been an important contribution.
The Equitainer is carefully engineered to give a repeatable and reliable cooling rate and final temperature that is substantially independent of external conditions. Although the performance of the Equitainer is good, the structure is relatively bulky and not inexpensive to produce. The cost of the Equitainer implies that the container must be returned to the shipper after use. In many cases, this can be inconvenient.
The conventional Equitainer achieves a required cooling rate by placing a sample in a conductive cavity, known as the Isothermalizer, and interposing a barrier between the sample and the coolant. This configuration determines the rate at which heat can be transferred between the coolant and the sample. The volume of the sample is then adjusted using thermal ballast, to result in a desired controlled cooling rate. The sample and coolant assembly is packaged inside a large insulated cylindrical container, and dispatched to the user. There is an initial cooling rate when the start temperature is at about 37xc2x0 C. of close to xe2x88x920.3xc2x0 C./minute. The cooling continues slowly en route, down to a minimum temperature typically 6xc2x0 C., depending on exterior conditions.
It has been shown and reported in the industry that the best results are obtained for horse semen fertility when the cooling rate at 20xc2x0 C. is in the vicinity of xe2x88x920.1xc2x0 C./min. This is to avoid a high rate of change to the cell temperature at the temperature where the lipid cell membranes are changing phase. The low temperature rate of change likely allows the proteins in the cell surface time to crystallize in an orderly fashion and avoid cell damage. The Equitainer design was based on this finding.
In addition to the Equitainer, a number of other conventional devices use a process of convection to cool the sample contained within the device. With convection, cooled air transfers heat from the sample to the coolant. The sample is normally transported in syringes ready for insemination, and a thermal barrier is introduced between the coolant and the sample to adjust cooling rate. The thermal barrier used is typically a Styrofoam sheet with one or more notches cut out. The Styrofoam sheet is placed between coolant block and sample, so that air can flow through the notches as it convects. The coolant block is normally placed above the sample. Cool air then falls through the holes in the Styrofoam and cools the sample. The sample is placed in a foamed plastic box, next to the Styrofoam thermal barrier and the coolant block.
The convection system does not independently control cooling rate and final temperature. In addition, the convection system is sensitive to orientation. This is evidenced by the fact that the cooling rate is about twice as fast when the system is upright verses when it is inverted, representing the difference between air convection cooling and air conduction cooling. To make a system in which the cooling rate is independent of orientation, convective cooling cannot be used. The failure to maintain a uniformly controlled cooling rate can have negative effects on the success rates of equine insemination.
There is a need in the art for a disposable container with similar reliable cooling rate properties as the Equitainer, but with the added constraint that the materials and components required must not only produce accurate and repeatable results, but must be simple, disposable, and inexpensive. The present invention is directed toward further solutions to address this need.
In accordance with one embodiment of the present invention, a storage and transportation container for storing and transporting a semen sample is provided. The container includes an insulated box having at least a first portion being a box protruding ridge, at least a second portion being a box recessed groove, and a floor. An insulated cover is provided having at least a first portion having a cover recessed groove and being located to receive the box protruding ridge only when the insulated cover is placed on the insulated box in a predetermined orientation. The insulated cover also has at least a second portion having a cover protruding ridge and being located to be received into the box recessed groove only when the insulated cover is placed on the insulated box in the predetermined orientation. A cooling pack is disposed on the floor of the insulated box. An insert is disposed to rest on the cooling pack inside the insulated box, such that the cooling pack is beneath the insert when the insulated box is in an upright position. The insert has at least one chamber for receiving a storage capsule holding the semen sample. The insulated cover frictionally fits on the insulated box and makes contact with the insert to hold the insert in place. The insert makes sufficient contact with the cooling pack to enable conductive cooling of the semen sample in the insert.
In accordance with various aspects of the present invention, the insulated box and the insulated cover are formed of foam plastic, such as Styrofoam, or the like. Likewise, the insert can also be made of foamed plastic, such as polyethylene, or the like. The choice of material rests on insulation properties and relative cost.
In accordance with further aspects of the present invention, the at least one chamber is sized and dimensioned to hold a storage capsule suitable for holding the semen sample. The semen sample is equine semen. The storage capsule is at least one of a syringe and a tube.
The storage capsule can be sized and dimensioned differently, and can include sizes with volume capacities of 20 ml or 50 ml. The relative size of the storage capsule will affect the number of chambers required in the insert to hold the storage capsules. Since the total amount of material to be cooled will affect the cooling rate, thermal ballast can be added to the storage capsule, if necessary, to keep the total volume in the range of 80 ml to 120 ml in one example embodiment. The thermal ballast is typically water, contained in a suitable tube, initially at substantially the same temperature as the semen sample. Smaller capsules would result in more capsules being required and thus a plurality of chambers required in the insert. A sum of the capacity of the semen sample and the thermal ballast able to be stored in the at least one chamber according to one embodiment is about 90 ml to about 110 ml, or about 80 ml to about 120 ml. With such a semen sample quantity, a cooling rate of the semen sample in the insert is about 0.1xc2x0 C./min at about 20xc2x0 C.
In accordance with further aspects of the present invention a method of packing a semen sample for storage or transportation includes providing an insulated box having a floor. A cooling pack is placed on the floor of the insulated box. An insert is placed on top of and substantially in contact with the cooling pack, the insert having at least one storage capsule holding the semen sample disposed within at least one chamber of the insert. An insulated cover is placed on top of and in contact with the insert, the insulated cover having a friction fit with the insulated box.