FREEZING SEMEN FROM YOUR STALLION

At the present time, the only way to tell whether or not your stallion's semen will freeze well is to try a test freeze. The two types of freezing used by our lab are the "fast" and "slow" freezing methods. An ejaculate will be split post centrifugation and tested with each one of these methods. Once the semen is frozen, a sample is thawed and checked for motility (progressive forward movement). If the post thaw motility is 30% or better, the sample is considered acceptable.

Freezing semen is different than processing semen for overnight transport. The semen is collected in the usual manner and the initial testing is the same. After this point the process changes. Initial testing involves checking the ejaculate for quality by determining the concentration of spermatozoa per ml, total volume and progressive forward motility. The gel free fraction is then diluted with a centrifugation extender and centrifuged to concentrate the cells. Once the cells are concentrated, the centrifugation extender and seminal fluids are removed from the sample with a suction pump and the cells are re-suspended in a second extender. This "freezing" extender used depends on the method of freezing. This extender can be  composed of egg yolk or skim-milk solids, sugars, buffers and a substance called glycerol which protects the spermatozoa from damage during the freezing process. 

From the initial testing on each collection, we have determined the total number of cells in the ejaculate. Each 1/2 ml pvc straw is then filled or "packaged" with the appropriate number of cells. The number of straws frozen per ejaculate is highly variable with each stallion. An average of 6 to 8 breeding doses, or about 40 straws can be expected from each ejaculate.

Current protocol is that the mare should receive a total of 800 million motile cells per insemination and two inseminations per cycle. The post thaw motility of each batch determines the number of straws to be used. For example: Let's say that upon our test thaw it was determined that the sample straw from a particular batch of straws had a post thaw motility of 50%. Since we know we have packaged 200 million cells in each straw, 50% of 200 million would be 100 million cells. Therefore it would take 8 straws per insemination to reach the required 800 million cell insemination dose.

Once semen is frozen it must remain in the liquid nitrogen environment. If it is properly stored and handled, the shelf life can be indefinite.

Please note that not all stallions freeze well. Even stallions that do freeze well may have particular ejaculates that may need to be discarded. It is also very important when choosing mares to be bred with frozen semen, that the best candidates are chosen. Frozen semen processing weakens the cell and reduces its viability. In order to be successful, it is important that each mare be carefully screened to give an optimum chance of conception.

FROZEN SEMEN: EXPECTED COSTS

You should have in mind the number of mares you would like to freeze semen to accommodate. After the first few collections a better idea of the actual number of straws per freeze can be determined. For projecting we can estimate about 40 straws per freeze or 6 to 8 breeding doses. Remember that each mare may take more than one breeding dose. We recommend you set aside at least 6 breeding doses per mare you intend to service.

The initial test freeze and each additional freeze cost $500.00. There is a straw printing charge of $135.00 and a monthly storage fee of $50.00.