Reproduction - Freezing Semen

We can collect semen from your stallion at our hospital which gives us total control of all the management of the semen from collection to freezing. Your stallion can be stabled in a stallion box or in a large yard. We most commonly collect and freeze the stallion semen at every other day intervals. The reasons for this will be explained later.

What is involved with freezing semen?

Most importantly we try to use semen that is not old or stored in the stallion’s reproductive tract. In order to achieve this we try to have the stallions sperm reserves depleted. Which means that all the sperm ejaculated will be freshly produced and therefore more capable of handling the stresses of centrifuging, freezing and then thawing. If the stallion is left without breeding for a week or so he may start to store semen and adversely affect the quality of our collection. In addition, the stallion produces sperm relatively constantly and spermatozoa produced take about 2 days to totally fill the extra-gonadal (outside the testicle) storage system after each ejaculation. This means that we only need to collect the stallion's semen every other day.

The Semen Freezing Process

Collection:
We collect semen using an artificial vagina (AV) that is filled with water and held warm at about 44oC. The stallion can mount either a mare in standing heat or a phantom. At Weatherford Equine we prefer to train the stallion to mount the phantom to reduce risk of injury to the stallion. At our facility most stallions can be successfully trained to mount a phantom within 1-2 days.

Centrifugation:
This process concentrates the semen into a small pellet. This is to ensure we can produce a small dose with a large number of sperm. The centrifugation also allows the removal of seminal plasma (the extra fluids that the stallion ejaculates with the collection) which is toxic to sperm if not removed.

Adding the cryoprotectant:
After the sperm have been centrifuged they are re-suspended in a mixture of protective solutions ready for freezing. Two important components of cryoprotectant are 1) Egg yolk and 2) Glycerol which provide nutrition to the sperm.

Freezing:
At Weatherford Equine we use the VAPOUR FREEZE method of freezing semen. The straws of semen are placed on a rack at a specific height above a pool of liquid nitrogen.

It is important to remember that some stallions freeze very well and the method of freezing doesn't really affect the outcome, Some stallions only freeze well under specific conditions and some stallions do not freeze at all no matter what tricks we might try.

Storage:
After the freezing program is finished the semen is stored in liquid nitrogen a -1960C. This temperature is so cold that
there is hardly any movement of atoms of the cells frozen. This means that the lifespan of these cells (spermatozoa) is
greatly prolonged and stallion semen has been frozen for over 20 years and has been found to be just as viable as the
day it was frozen.

STORAGE Your stallions frozen semen can then be either;

  • sent to you in a Dry shipping container
  • stored by at Weatherford Equine for later use or,
  • stored at a facility that is designed for long term, high volume storage – like Beef Breeding Services ROCKHAMPTON

OR Genemovers.

Costs

Our charges are $500 per collection & freeze.

Thawing

Mostly we thaw semen at 370C in a water bath. There are variations and we try to look at them all. After the semen is thawed we look at the individual spermatozoa to assess motility.

Success

General conclusions on Frozen Semen:

  • 30% of stallions in the general population will freeze well
  • 40% will be probably be classified as satisfactory
  • sperm from the remaining 30% will not survive the freezing process with a level of motility sufficient to be used for AI.