by R. Atwood
February 4, 2008
Progesterone is a hormone that is released during ovulation. Monitoring of the Progesterone levels during the heat cycle (estrus) can help maximize the success of a breeding. Many breeders credit Progesterone testing as the reason for minimized singleton litters, increased litter sizes, and better success for predicting due dates.
Progesterone levels are monitored by taking a blood sample to the Vet. There it will be spun and separated after which the Vet will send the sample to a Laboratory for the actual testing. The Lab will return the results of the test to the Vet the next morning. The result is a number (in nanograms, ng) which is the measure of progesterone. In our area, the cost of Progesterone testing is just less than $100 per test which adds up, but the results are proven.
The progesterone level of a female that has not ovulated in the past two months is near zero. At the beginning of the heat cycle the Progesterone level will measure 0.1, 0.2, and 0.3 and may go up and down between those numbers. From there the Progesterone level will begin to rise. There is typically no need to test Progesterone very early in the heat cycle since ovulation doesn’t usually occur until after day 7. We begin testing Progesterone every other day starting around day 6. In Airedales we have typically found that the ovulation day is almost always about day 14. Ovulation occurs when the Progesterone reaches 5.0.
Luteinizing Hormone (LH) also plays a part in Progesterone testing and breeding. The LH surge is what causes the ovaries to release eggs. LH can be tested along with Progesterone, however, most breeders just test the Progesterone. We have never used a Reproductive Vet who asked for LH testing. Ovulation occurs about two days after LH surge.
Some females may have Progesterone results that hover around 3-4 for a couple days, other females may not. Sometimes the guidelines for progesterone are adjusted slightly when the progesterone level spikes drastically without the hovering. Also, in the case of a female with Progesterone that may reach 3-4 and then drops, there has been a split heat cycle. The second part is the most fertile of a split heat cycle. The progesterone testing continues every few days until the level rise again and ovulation occurs which might be a month later.
After ovulation it takes about 2 days for the eggs to become fertile. The eggs stay fertile for about another 2 days after that. With Progesterone testing you are able maximize the time that the stud’s sample has with the fertile eggs.
Breeding based on Progesterone depends on the method being used and the sample type. Fresh samples can remain fertile for about 3 to 5 days or more. Fresh chilled samples last about 1 to 2 days in the uterus. Frozen samples may remain fertile for less than a day (12-24 hours). Using a fresh sample the best result is breeding on the second day after ovulation and the fourth day. Using fresh chilled the breeding should be the second day after ovulation. With frozen samples the breeding is typically done on the third day after ovulation. Frozen breedings are typically done via surgical implant for the best results.
There are guidelines based on the type of breeding also. For a standard Artificial Insemination (AI) the breedings are typically on day 4 and day 6 after the Progesterone reaches 2.0. Another common guideline is day 2 and day 4 after ovulation, when the progesterone level reaches 5.0. It is important to continue Progesterone testing past the 2.0 level because, as stated before, some females might hover around 3 to 4 for a couple days before reaching 5 and ovulating, while other females may not. Surgical Implants are typically done 48 hours after the Progesterone hits 5.0, except when using Frozen as stated above.
Calculating the due date of the litter is easier when using Progesterone testing also since you know when ovulation occurred. The due date is 63 days after ovulation occurs regardless of how or when the breeding took place.
Progesterone levels may peak anywhere between 15 and 80 ng/mL. Progesterone levels will gradually decrease over the following five or six weeks until they are back to the 0.x level in a female that is not pregnant and remain down for four or five months until the next heat cycle. However, if the female is pregnant the progesterone levels will remain elevated in order to maintain the pregnancy. Just prior to whelp the progesterone drops back down and correspondingly the temperature of the female also drops to about 99 or 98 degrees Fahrenheit (average canine temperature is 101.8 degrees Fahrenheit).
The image below shows the typical lab results following a progesterone test. The lab typically posts the results of the test and your Veterinarian will call you with the number. If you request it, your Vet should be able to send you the actual test results similar to what is shown below, however, the number (level) is the only really import piece of information on the results form.