Ovulation: Timing is Everything
By Katherine Settle, DVM
As breeders, many of us have been successfully breeding
dogs for a long time. For the most part, we breed
when the bitch #8220;says#8221; she#8217;s ready and the stud #8220;says#8221; she#8217;s ready. Ovulation timing is important
because 75 percent of the missed breedings can be
contributed to improper timing of the breeding. Since
some of us are now in a new age of long-distance breeding,
where the bitch and stud stay at home and the semen
travels, timing the bitch#8217;s ovulation is critical.
By keeping accurate breeding history
records, we can get an idea of future heat cycles.
Always keep a record of the date, the day of the cycle
the bitch was bred, the results of the 30-day pregnancy
ultrasound or test results, the date of whelping,
and the number of pups. Even if the bitch was not
bred, you can get an idea if the cycle was long or
very short and when she began flagging.
Do your homework in
hopes that your biggest worry will be the
sleep that you lose on whelping night. Border
Credit: Isabelle Francais.
There are three ways to help us determine ovulation
in a bitch. By doing vaginal smears on a bitch, we
can get an idea of when she should be receptive. If
we continue to do vaginal smears, we can determine
the day that the smear makes a 20 percent change back
from cornified (superficial and anuclear cells) to
non-cornified (para-basal and intermediate superficial
cells). This smear is called a diestrus smear. If
we count back 6 days, that is the approximate day
of ovulation. Another post ovulation way is to count
back 63 days from whelping. As you can see, neither
of these is helpful for the current breeding cycle.
So the best way to time ovulation is with hormones.
Progesterone is the hormone we use most often.
Some progesterone tests are run in the veterinary
hospital and give a range of numbers, such as 3-10ng/ml.
This may be adequate if you are doing multiple tests
and plan a breeding with the male present. If we assume
that male sperm can live around six days, you can
afford more flexibility with the timing. However,
with chilled semen we assume the cooled sperm can
survive about three days, one in travel and two in
the bitch. Frozen, we assume about 12-hour sperm survival,
and the timing must be even more accurate. A radio
immune assay progesterone (RIA) is the most accurate.
RIA#8217;s give you a result in a number,
like 3.2ng/ml. Always check the laboratory turn-around
time and the cost. Another test, LH, can also be done
in the veterinary hospital, but I only use it to help
support my progesterone result.
I usually begin my progesterone
testing around day 5 of a three-week cycle. Sometimes,
I use the vaginal smear to tell me if progesterone
testing would be too early. I repeat another progesterone
depending on the previous progesterone result. The
initial rise in progesterone represents the LH peak.
Usually this is when the progesterone is around 2ng/ml.
Two days later, I expect the progesterone to be within
an ovulation range, which is around 3.5-5ng/ml. In
a bitch (which is different from people and horses),
the eggs are not ready to be fertilized when they
are ovulated. They must go through another change,
and are ready one to five days after ovulation. Using
a bell curve and playing the averages, most bitches#8217; eggs are ready to be fertilized
on day 3 after ovulation, less on days 2 and 4, and
even less on days 1 and 5. So when breeding artificially,
we put chilled semen in on day 2 after ovulation,
thus the sperm cover day 2 and 3. For frozen we inseminate
on day 3. Also, with frozen, semen should always be
put into the uterus using surgical insemination or
insemination by rigid endoscopy (TCI, Trans Cervical
Insemination). In your planning stages for the desired
breeding, be sure to check with the people on both
ends about their availability to collect the male
or inseminate the bitch. Can they be available on
a Sunday? Also, remember that overnight deliverers
currently do not pickup on Saturday or Sunday. If
airlines are to be used, the person shipping must
be a known shipper (Check with airlines for registration
requirements). Sometimes, we must just work around
these problems, which means we may have to settle
for a day before or after we would have preferred.
Keep accurate breeding
history records to get an idea of future heat
In using these tests, we are basing our interpretation
on averages. Also, not all bitches #8220;read the book,#8221; and many will have test results
that do not follow what we expect. With these bitches,
we evaluate all the tests and clues and use our best
Do your homework and plan properly in hopes that your
biggest worry will be how much sleep you lose on whelping
Dr. Katherine Settle, along
with her veterinarian husband, John Schontz, own two
veterinary practices. Settle has been working in canine
reproduction for more than 24 years.
Article may not be reprinted without permission.
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