Breeding horses today can involve the use of artificial insemination with fresh, chilled or frozen/thawed semen. Whether you are using AI or natural cover the main objective is to get viable sperm to fertilise a healthy oocyte (ovum or egg).
Chilled Semen
Artificial insemination with chilled semen involves the collection, evaluation and dilution of semen from a stallion. After that infusion of an adequate number of sperm into the mare’s uterus at the right time is essential. Semen from most stallions can be transported to the mare within 12-48 hours after collection. In recent years clients have successfully used chilled semen from Germany, The Netherlands, Belgium, Scotland, Ireland and stallions based in the UK.
Some semen can be stored for up to 72 hours but chilled semen from most stallions is viable for a maximum of 48 hours.
It is therefore important that the mare is inseminated as close to ovulation as possible and as soon after semen collection as possible. If all goes according to plan, a conception rate >70% per cycle can be achieved.
Timing is critical with chilled semen and delays can be very costly. With the use of chilled semen it is important for the receiving veterinarian to predict the time of ovulation in advance so that semen can be collected and transported.
Why is semen cooled?
Fresh semen deteriorates rapidly at 37 ºC. Raw ejaculates will have no motile sperm after 3-4 hours at 37 ºC and 5-7 hours at room temperature. The main reason for this is that seminal plasma, the fluid component of the ejaculate, has a very low buffering capacity and by-products accumulate as a result of the high metabolism of the spermatozoa. Extended semen however can be stored at room temperature for up to 12 hours ideally in a light proof, airtight container.
If semen has to last longer than 12 hours it should be cooled down to 5-8 ºC.
Cooling semen (to 5 ºC) slows sperm metabolism, fewer waste products are produced (lactic acid, CO2) and therefore less cellular damage occurs. When spermatozoa are stored at 5 ºC their metabolic needs are only 10% of what they are at 37 ºC.
Why extend semen?
- To permit effective antibiotic treatment of semen, thereby reducing bacterial contamination
- To prolong life of spermatozoa
- Enhance the viability of semen from some low fertility stallions
- To protect spermatozoa from unfavourable environmental conditions
- Increase volume of the inseminate
- Allow better semen evaluation
If semen is used within 6 hours after collection, maintained at room temperature and extended, 1:1 or 1:2 would be a sufficient dilution to preserve its motility and fertilising potential. However when the semen is not used until 12-24 hours after collection, it should be diluted at ratios 1:3 to 1:10 depending on the total volume and total sperm count, ideally up to a sperm concentration of 25 to 50 million cells per ml. In addition it should be slowly cooled to 5-8 ºC.
The insemination dose required to inseminate a mare is the number of sperm deposited in the uterus, this should not be confused with the volume of the insemination dose.
Longevity and fertility of processed semen is determined by;
- Quality of the raw ejaculate
- Dilution rate
- Rate of cooling and storage temperature
- Storage time and container
- Type of extender
Once the breeding cycle of your mare is established she will be monitored closely and our veterinarians will directly order semen when the mare is close to ovulation. After collection of the semen transport normally will take between 12 and 36 hours depending where it has to come from. The mare is inseminated as soon as the semen has arrived.
Costs
A certain number of rectal and ultrasonographic examinations and or medical treatments will be required pre and post insemination to ensure the highest chance of conception. These treatments will vary depending on the individual needs of your horse.
Drugs regularly used are;
- Chorulon (hCG)
- Intra Uterine Antibiotics
- Prostaglandin
- Oxytocin
- Progesterone
The time your mare will be required to stay at the practice or at stud will vary due to a number of factors:
- age of the mare
- maiden, barren or foaling mare
- damage to her reproductive tract due to previous foaling, abortion or placentitis are all important towards her future fertility and breeding potential (Most of the potential difficulties can be overcome by medical or sometimes surgical treatment of your mare when necessary)
- quality of the semen
- success of the initial insemination or consecutive attempts
AI with chilled semen can also be done at home. Some clients wish to keep their mare at home instead of at the practice. Fortunately AI using chilled semen allows this without compromising the pregnancy rate of the mare.
Individual arrangements can be made.
Costs include:
- Visit fee
- Rectal and ultrasonographic examination of the mare
- Use of drugs to manipulate her cycle when necessary
- Insemination of the mare and microscopic assessment of the semen
- Re-visits and pregnancy diagnosis
The mare owner has to make arrangements with the stallion owner with regards to:
- Choice of stallion
- Stud fee and transport costs of the chilled semen
- The address the semen has to be send by stallion owner (practice/ stud/ home)
Our veterinarians are more than happy to advise you when you have questions or queries.
Please contact us on 01283 799700 or visit our Equine Practice after consultation with our office or one of the vets.
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