INSEMINATION WITH FROZEN SEMEN: SIMPLIFIED
Insemination with frozen semen does not have to be complicated, expensive or time consuming. The reputation that frozen semen has gained for being “difficult” to use is unfair, and developments during the last decade have led to the design of a protocol which removes the need for intensive monitoring, that has long been believed to be necessary in order for “frozen AI” to be successful. It is acknowledged that the best pregnancy rates are achieved when the semen is inseminated no more than 12 hours before or 6 hours after ovulation, as frozen-thawed semen has a shorter lifespan than chilled semen, once inseminated, and post ovulation inseminations lead to a higher rate of early pregnancy loss than pre and peri ovulation inseminations. Consequently, it has been suggested that monitoring by rectal palpation should be performed as often as every 6 hours, or by ultrasound every 12 hours. This is both impractical for the average veterinarian, and expensive for the mare owner.
However, there is a more “user friendly” protocol for insemination of frozen thawed semen.
Research in Italy performed by Sandro Barbacini in conjunction with Select Breeders Services (Colora, MD, USA) resulted in the development of a timing protocol that produced pregnancy rates comparable to those achieved using more labour intensive methods. The protocol is as follows:
- Upon an estrus mare's follicle reaching a diameter of 35 mm, the mare is given a suitable dose of hCG (typically a dose of around 2,500 i.u. for a mare up to 650kg - overdosing may result in prevention of ovulation). Prior research has indicated that ≥80% of mares will ovulate within the 48 hours following the hCG dosage.
- The mare is then inseminated 24 hours after receiving the hCG, and again 16 hours later, at 40 hours after receiving the hCG. Use of this timing protocol will result in the majority of mares being inseminated within the 12 hours prior to or 6 hours after ovulation and provides coverage for ovulations occurring anywhere from 18 to 52 hours after the administration of hCG.
Another significant advantage of this timing protocol is that if initiated at the correct time, it will require the veterinarian to administer hCG and perform the insemination at 5:00 pm, and the second insemination at 9:00 am. These times are generally close to the first and last calls of the regularly scheduled day for the veterinarian, and can be easily completed without interfering with other calls or much needed sleep!
The use of the timed insemination protocol calls for the second insemination to be performed at a time when uterine inflammatory response may be severe (16 hours after the initial insemination). We therefore advise mare owners to select fertile mares with no known history of delayed uterine clearance, and to not hesitate to use an oxytocin protocol treatment starting 4 hours post-breeding and repeating treatment at 6-hourly intervals if evidence of uterine fluid or prolonged inflammatory response is present.
It should be noted that some practices in the UK are now having very high success rates with frozen semen (comparable with fresh and chilled), with some reporting higher seasonal pregnancy rates with frozen semen, than with fresh & chilled semen!
This article was originally written by (and the image is copyright of) Jos Mottershead of Equine Reproduction LLC, OK,USA (http://www.equine-reproduction.com), and has been adapted by Jamie Anderson of Equine Reproduction Ltd, UK.
don't be scared...
- Frozen semen is a fantastic tool, and we think that it's a great shame that it has such a poor reputation in the UK.
Please feel free to pass this information onto your veterinarian, and encourage them to use this protocol. Also, please let us know if you've had good or bad experiences with frozen semen!