Nowadays, as breeders we have more tools to our disposal for successful breedings. One of them is the progesterone blood test.
Not everybody understands the value of such test, and here we would like to explain what we have learned. In no way do we want to replace your veterinarian or your reproduction specialist. We supply this gathering of information for your understanding.
With the visiting female, we try to find the LH Surge. LH is short for Lueteinizing Hormone, which is the biological trigger leading to ovulation. The LH surge is the central timing event of the bitch's cycles. The blood progesterone level is the # 1 way to accurately determine the optimum fertile period in the bitch.
We have a responsibility as breeders to ensure the visiting female to be served the best way we can; the blood test remove a nervousness about the timing. But of course, Calif is the one that will know when the breeding can start. One visiting bitch was breedable on the 16th day after her first vaginal blood while another was breedable on her 8th day. No two females are the same
Estrus: Is the period of receptivity. In terms of hormone, this begins on the day of the LH surge and is marked by rising progesterone levels while the estrogen levels are decreasing.
Diestrus: Normally begins 7 to 9 days after the actual LH surge. Progesterone levels continue to rise. The vaginal cornification abruptly declines.
On the right, you can see a portion of the Laboratory Results and Interpretation of a Progesterone Blood test.
A single progesterone value will give one of three results: low, mid range, or a high progesterone level.
If the level is very low then you know you have at least 4 days or longer before a breeding will be needed.
If the level is mid range (2.0 to 4.0 ng/ml) you need to start breeding within two days; if the level is high (>5.0 ng/ml) you should start breeding immediately; if the level is very high (> 15.0 ng/ml) you need to evaluate if the bitch is still in season and if she is, breed ASAP.
Breedings beginning when the bitch already has a very high progesterone may be too late and you will need to start sooner for subsequent breedings.
With all these processes occurring, it takes several days for a canine oocyte to become fertilizable, at least three to four days after the LH surge. However, within two days after they have matured to a fertilizable state, the gametes begin to degenerate. The upshot of all this is that the bitch is only fertile for about four days during her whole cycle if all the eggs are ovulated at nearly the same time. It is, however, fairly common for the eggs to be ovulated over a 18 - 36 hour period thus lengthening the fertile period.