Semen Freezing

Artificial Insemination (AI) is a popular and routine procedure for breeding sports horses. Rossdales' semen freezing service allows evaluation of the suitability of stallions for semen freezing. Our Defra-approved semen laboratory uses the latest equipment and techniques for freezing, storage and shipment of semen to all major markets around the world.

Semen collection and initial analysis

Semen is collected using an artificial vagina following the mounting of a dummy mare by the stallion. This can be performed either at a local AI centre, or at your own premises if suitable. Penile swabs for venereal disease and blood sampling for infectious disease must be taken prior to semen collection or entry onto the stud. Initial semen analysis involves assessment of morphology, motility, volume and total sperm count.

Test Freeze

Following initial collection, the semen will then be subject to a test freeze. This involves using various extenders to assess which medium provides the best post-thaw support to the semen. The semen is then subject to centrifugation. This concentrates the semen into a sperm pellet, which is then re-extended into the various extenders containing the cryopreservant. The semen is then placed into straws and chilled prior to freezing. Following cryopreservation (freezing), the straws are then thawed and semen is assessed under the microscope for morphology and progressive motility.

Semen must be at least 35% progressively motile following thawing of frozen semen to be commercially usable. Each ejaculate will provide approximately 5-10 insemination doses. Each dose usually contains 6 straws and three doses should be provided for each mare inseminated. The total number of doses frozen will depend on owner requirements.


Frozen semen will be taken to a local AI centre for storage and shipping. Following successful cryopreservation, an information sheet will be provided to you and the stud regarding the semen, dosage and thawing instructions.

Problem Stallions

It is known that a percentage of stallion's semen will fail to freeze well and some may not freeze at all. In such cases these stallions require advanced testing consisting of trials with other extenders, and with alteration of the freezing and thawing processes. Some stallions that have problems mounting the dummy may have semen collected using a chemical ejaculation technique.

Epididymal recovered semen

In the event of death of a stallion or sudden requirement for castration, epididymal recovery of semen can be performed and the recovered semen can be frozen for use at a later date. Testicles must arrive at Rossdales within 24 hours of death/castration and must be shipped cooled, but not on ice. In an ideal situation the testicles will arrive as quickly as possible. Although this is a fairly simple procedure, it must be noted that often semen recovered in this way is immature and devoid of seminal plasma. This, alongside the inability to test freeze the semen, may result in poorer post thaw fertility. Often upwards of 30 doses of semen can be frozen in this way.

For further information about our semen collection, analysis and freezing services, please contact our Newmarket office on +44 (0)1638 663150. Alternatively, contact Andrew McGladdery or Fred Barrelet.

Artificial Insemination