Progesterone is a hormone that is present in the female dog. It is produced in the ovaries. A characteristic of progesterone is that it increases in concentration as the bitch is ovulating. It’s concentration increases rapidly as the bitch approaches her ovulation peak.
The purpose of a progesterone test is to determine when the ovulation takes place. Without an ovulation the conception cannot take place even though the semen of the stud dog is of excellent quality. “Timing” is the most essential factor.
“Timing” is of essence when:
- An old stud dog is used with a reduced libido
- A stud dog is used whose semen is of lesser quality
- A stud dog is used who has to mate 2 or more bitches in a short period of time.
- Frozen or chilled semen is used.
- The whelping date has to be determined in advance (dog breeds where caesarian are indicative)
- A bitch that shows little or no symptoms during the estrus.
- When the owner of the bitch has to drive a long distance to visit the stud dog. In such situations it is always pleasant to know that one is leaving at the correct time/date.
One has to take into consideration that not every bitch follows the hormonal cycle according to the book! Research has shown that the ovulation peak can take place anywhere from day 7 until day 22 of the estrus cycle (3).
N B: It should be taken into consideration that not everyone takes into consideration as to when the estrus cycle of the bitch has taken place. Some bitches display little or no signs of estrus (vaginal discharge and interest in male dogs). It is therefore possible that a bitch in fact could be further with her estrus cycle than originally expected.
My advice to my clients is to start on day 7 of the estrus cycle. Depending on the results of the first blood results can a protocol be made with regards to further testing.
Progesterone results from the past are no guarantee with regards to the current estrus cycle.
Unfortunately there is no guarantee for this. A correct progesterone result (dependant on the type of test used) is only an indicator that the bitch has reached her ovulation peak. Other factors have to be taken into consideration such as the following:
- Harmful bacteria that can be located in the vagina and the uterus.
- The ovaries or the oviduct malfunction.
- Quality of the semen used
- Health condition of the bitch (illness)
The progesterone concentration begins to increase on average 2-3 days before that the ovulation peak is attained (2,3). At this point another hormone is released (Luteinizing hormone) which causes the ovulation to take place. This unique hormonal encounter allows one to be able to determine when the bitch has to be bred.
It is more difficult to measure the Luteinizing hormone in comparison to that of progesterone. The Luteinizing hormone release is also of a short period (1-2 days)(2,3).
The advantage of measuring the progesterone concentration is that it’s increase can be measured gradually throughout the estrus cycle. The ovulation peak occurs 2-3 days after the Lutenizing hormone peak, and the conception can take place 4-6 days after the Lutenizing hormone peak has taken place (3).
There are many types of progesterone tests available. Most of the available tests are based on that of radioimmunossay (RIA) or that of an enzyme-linked immusorbent assay (ELISA).
Another method is to take a vaginal smear and to examine this under the microscope (1). During this examination the changes in the cell structure (epithelial cells) are examined. Depending on the changes can an estimate be made as to when to breed the bitch.
On day 1 of the estrus cycle I advise the owner of the bitch to have bacterial examination done of the reproductive tract to determine if there are any bacteria that can have a negative influence on the fertility. The owner of the bitch comes to the clinic with his bitch on day 7 of her estrus cycle were a blood sample is taken (1-2 ml). This blood sample is placed in a centrifuge machine from which the plasma is separated. Afterwards the plasma is removed and used for the progesterone test.
Depending on the result is it possible to give advice as to when another test should be done or to advice the owner as to when to have their bitch mated.