Ovulation timing is a valuable tool in any breeding plan. It allows us to determine when to breed a bitch to optimize the chance for pregnancy, as well as achieve pregnancy in many bitches thought to be infertile. Timing is essential for specialty breeding when using fresh-chilled and frozen semen, and can also help us accurately predict due dates.
It will help you to understand the bitch’s heat cycle (estrus). As you probably know, female dogs come in heat about twice a year. The heat will last about 3-4 weeks, and in the normal course of breeding, the bitch will stand to be bred somewhere between 8 and 15 days along. This varies a lot, and some bitches need to be bred as early as 4-6 days, others as late as 20-30.
The three most important hormones in the bitch's estrous cycle are progesterone, L.H., and estrogen.
Progesterone testing also helps our veterinarians determine ovulation. Progesterone is also normally at very low levels, then as the heat cycle progresses, progesterone will show a rise. Unfortunately, there is not a single number for determining the exact ovulation date. Our veterinarians look for a result between 4ng/ml-8ng/ml to determine baseline for beginning of ovulation cycle. As progesterone timing continues we look for a distinctive rise from the initial baseline results.
Progesterone remains elevated for 8-9 weeks (gestational period) whether or not the bitch is pregnant or was bred. At the end of the pregnancy (or non-pregnancy), the progesterone will begin to drop. The drop in progesterone causes labor to start and is also responsible for the symptoms of false pregnancy.
Luteinizing Hormone (LH) actually causes ovulation. LH remains at very low levels in the blood, then suddenly surges two days prior to ovulation. The eggs must mature before they become capable of being fertilized. The eggs are mature for only a few days, after which they deteriorate if they have not been fertilized.
It is possible to test for the LH level, and this is actually the most accurate way to do it. However, since LH is only elevated for a short time (as little as 18-24 hours), blood must be drawn at the same time daily until ovulation is confirmed. Rose City Veterinarians strongly recommend LH testing for frozen semen breeding or bitches thought to be infertile.
Estrogen causes the vulvar swelling, bleeding, and the changes in the vagina that Rose City veterinarians use to do "vaginal smears." Estrogen is the hormone that causes the bitch to act receptive. In most bitches, estrogen rises anywhere from 5 to 20 days before ovulation. Because of this very wide range, vaginal smear cytology’s are only a rough estimate of cornification of cells in the vaginal canal. Vaginal smears play no active role in confirming ovulation.
After discussing your breeding plan with a veterinarian during your pets Pre-Breeding office visit we will start the ovulation timing process.
If the ovulation timing requires daily blood draws we also offer boarding services at an additional charge. Speak to one of our veterinary care staff members to schedule your pet’s appointment.