The first day of the estrous cycle is defined as the first day of vaginal bleeding, designated day one of proestrus. There is a tremendous variation between bitches as to the length of proestrus and estrus, sexual receptivity, and ovulation. It is not possible to predict ovulation from evaluation of the color of discharge, firmness of the vulva, behavior of the bitch or stud dog, vaginal smear or the number of days since the onset of proestrus. After natural breeding, sperm can survive in the female tract for 3-6 days. After artificial insemination with fresh, chilled or frozen semen or when breeding a sub-fertile bitch or stud dog, this time of sperm longevity can be greatly reduced. Ovulation timing done to ensure sperm are present when ova are ready for fertilization. Ovulation timing is also VERY helpful to more accurately predict whelping dates!
The evaluation of serial blood progesterone levels prior to ovulation (during proestrus and early estrus) allow us to most accurately predict ovulation. Rather than wait until a specific level is reached, we evaluate the baseline, first rise, and rate of rise to determine ovulation. In general, values less than 1.0 are baseline, and increases to 1.5-2.5 are consistent with an initial rise, but this can vary greatly. Many bitches have progesterone levels that go up and down before completely rising. After ovulation, progesterone will continue to rise and will maintain high levels (>10) for approximately two months regardless of pregnancy status.
Progesterone testing can be done anytime during regular office hours at VMC. You do not need to schedule an appointment with Dr. Callahan or another DVM, but please do schedule a drop in appointment for the technician to drawthe blood sample Currently , all progesterone tests are sent to Antech and results are usually available within 24 hours . We do require an examination before the first sample is drawn aa so that we can know what your plan for the breeding is (natural, side by side A/I, fresh chilled or frozen semen), and plan accordingly. Begin progesterone testing by day 5-7 of proestrus (day 1 = the first day blood is seen). If any doubt, you can start sooner. Food does not need to be withheld. Once the progesterone values are changing, in some cases we may ask you to start daily timing to be more specific.
Please have your DVM follow these instructions: Submit whole blood (plain RTT) to Antech lab only. We cannot compare results from different laboratories, so using Idexx or another lab will not allow us to compare values correctly. Do not use a serum separator tube. If obtaining serum for another reason, transfer serum to a plain RTT for progesterone submission.
If testing at your local hospital, please have your DVM contact you with the results as soon as they are available. The call us as soon as you have them. Please do not rely on faxes or copies of lab reports to be sent.
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