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Timing Follicle is
Essential
The success or failure of a breeding program lies, to a large extent, on the
timing of breeding the mare. Each mare will vary in the time she spends
completing the estrous cycle and the time it takes to develop the follicle and
release it. This pattern will generally follow a trend that will repeat
itself in successive cycles. Record keeping on each mare will help you
understand and allow you to follow her successive cycles and estimate the
follicle drop more precisely.
We have found that Shires can have a rather erratic follicle development.
They may develop a follicle that will reach 45 to 70 cm and can hold it from 4
to 5 days before releasing it. This can make the timing for breeding very
unpredictable.
Often, when a follicle is large and held for a number of days, it increases the
chance for a follicle to regress and not complete its drop. When the
follicle regresses in size and loses its shape, it may dissipate and your
chances for conception during that cycle have been eliminated.
Enhancing follicle drop with chemicals is the best method of developing a more
predictable time for follicle drop. There are several on the market and the
method of use is critical to the success you will have with them. HCG is
the most common and least expensive. It is not very forgiving of mismanagement
in timing. HCG in Shires needs to be injected when the follicle is around 38 to
40 cm. Earlier timing is not as effective and later on in the follicle
development it often is not effective. Generally within 30 to 36 hours after
injection you will see follicle drop. Desirellen is another product that
gives similar results and is much more forgiving of timing. It will work on a
wider range of follicle sizes. It however is much more expensive to
administer.
These drugs are very beneficial in aiding the timing of follicle drop when you
are shipping cooled or frozen semen. By following this schedule you will find
that the drop will be more predictable and you will consequently have better
timing for depositing semen into the mare.
For example if you ultrasound and find a follicle between 30 and 35 you need to
call the shipper of the semen for the next day delivery. Administering the
HCG or Desirellen on the morning of the day it is to arrive will give you about
a 5 to 6 hour head start on follicle drop. This close timing should prove
beneficial to getting the follicle to drop at or shortly after insemination.
The follow up breeding can be accomplished the next day and then in 24 hours
from that insemination you should palpate or ultrasound again to make sure that
the follicle did in fact drop and you are on schedule with your breeding
program. If the follicle did not drop then a rebreeding that day would be
in order. If you are using cooled shipped semen the timing of that
breeding and getting the semen shipped again may not work out and you may have
to plan a rebreeding on the next cycle. If you are providing natural cover
and the stallion is on site it is not a problem to cover the mare again on the
3rd day.
This is a great help when artificial insemination is being done and especially
when frozen semen is used in your breeding program. This, like anything
else we depend on, is not always 100 percent effective, but it is highly
predictable and is a great management tool that can be utilized in your breeding
program.
The cost of Desirellen is rather high as it is relatively new on the market.
Each case would need to be evaluated to determine if the added cost is worth its
use. The mare may not develop a tolerance to Desirellen like has been
reported of HCG.
When shipping cooled or frozen semen, it becomes of special benefit to help
determine when breeding can take place for effective results. When mares
tend to hold the follicle too long, they increase the chances of not completing
the cycle properly. This product can provide a method of reducing the time
and allowing for a better chance at conception. This tool must be evaluated by
you and your veterinarian to see if it would benefit you in your breeding
program.
For More Information Contact:
Jenson American Shires
9110 P-35, Blair, NE 68008
Tel: (402) 426-3198
FAX:
Internet:
ClarkJenson@huntel.net
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