Frozen vs Cooled Semen
Generally, any time you manipulate semen, the per-cycle pregnancy rate decreases. The rate should be highest for fresh
semen, then shipped semen, followed by frozen-thawed semen. This assumes a reproductively healthy mare and stallion. Per-cycle
pregnancy rates with frozen-thawed semen are reported to range from 0 to 70%.
Therefore, it is important to do a little homework prior to choosing to use frozen semen. It is important to know the first-cycle
pregnancy rate for that stallion's frozen-thawed semen. This information is also important when using shipped-cooled semen.
Next one needs to know how the mares were bred to achieve this pregnancy rate. Were the mares bred before, after, or before
and after ovulation? Also, were the mares bred with a full dose (and what constitutes a full dose for that particular stallion)
or was a dose split in half to allow breeding before and after ovulation? Was the semen deposited in the uterine body or was
deep horn insemination used?
In order to achieve the stallion's reported pregnancy rate, you must be able to repeat the breeding management used to
obtain those rates.
Mare selection also plays a role in the success or failure of frozen thawed semen. A reproductively healthy mare should
always be used when fertilizing with frozen-thawed semen. Older maiden mares should be avoided because the cervix is not able
to relax properly in many of these mares. There is an inflammatory response to insemination with frozen-thawed semen. One
aspect of an inflammatory response is fluid production by the uterus. If the cervix does not relax properly to allow the fluid
to escape, the inflammation increases (as does fluid production and accumulation), and a vicious cycle begins. There is more
effort and cost associated with the use of frozen-thawed semen, but this can be decreased if multiple doses of semen are available.
In conclusion, success with frozen-thawed semen is stallion- and mare-dependent. If you have a reproductively sound mare and
can find a stallion that has good fertility with his frozen-thawed semen, you can be successful. From TheHorse.com
(Artificial insemination of the mare with
chilled or frozen semen)
Today’s breeding technology provides horse owners more options than were available in the past. Artificial
insemination with chilled or frozen semen makes it possible to ship stallion semen all over the world.
Regardless of the method used, a breeding contract should be arranged, and the mare should have a
breeding soundness exam performed prior to breeding. When the mare comes into estrus, or heat, an ultrasound is performed
to determine how close she is to ovulation. Ultrasonography is used to determine the optimum time for insemination,
and hormones can be used to induce ovulation at the appropriate time.
When breeding with chilled semen, the semen is usually ordered from the stallion owner the day before she
is to be bred. The stallion is collected, and the semen shipped in a specially designed container, either an Equitainer,
or one of the less costly disposable containers. In some instances, the semen may be transported by air, arriving the
same day it is ordered. Once it arrives, the condition of the semen is assessed, and it is placed within the uterus
of the mare using a pipette. The mare is ultrasounded post-breeding to verify that she has ovulated in a timely manner,
and to assess fluid retention. Fourteen to sixteen days after ovulation, the mare is ultrasounded to verify pregnancy,
and to rule out the presence of twins.
The use of frozen semen to breed mares requires more exact timing of ovulation to insemination. Conception
rates are lower when frozen semen is used, as opposed to chilled semen. The major advantage of frozen semen use is the
ability to store viable semen for prolonged periods of time, thus allowing shipment over great distances, or the use of semen
from a stallion which is not currently being used for breeding. Two protocols are commonly used. In the first, more
traditional method, the mare is ultrasounded every eight hours until ovulation, at which time she is inseminated. This
method is very labor intensive. More recently, a protocol has been introduced in which two inseminations are performed,
closely timed in relation to administration of a drug which causes ovulation. This is less labor intensive, but requires
the use of two insemination doses.
Artificial insemination is a valuable tool in the equine breeding program. Good communication between
stallion and mare managers is essential. Depending on the situation, some additional diagnostics, drugs or technologies
may be necessary, as determined by your veterinarian. For more information, please contact your veterinarian. From Clearylakevets.com