Canine Estrous Cycle and Breeding Management
The canine estrous cycle is composed of four phases.
- Proestrus is one of the phases commonly called the heat or in season cycle. During this cycle the bitch attracts males but is not receptive for breeding. A uterine origin, blood tinged discharge presents and the vulva becomes moderately enlarged. The cells change from non-cornified to cornified cells due to an increase in estrogen. This phase can last from 3 days to 3 weeks with the average being 9 days.
- Estrus is also called the in heat or in season cycle. During this stage, the bitch enables breeding as estrogen declines and progesterone increases. Vaginal discharge diminishes and the vulva is flaccid. The vaginal cytology is 80 to 100% cornified. Red blood discharge usually diminishes, but at times can persist.
Luteinizing hormone (LH) triggers ovulation with immature, infertile eggs approximately 2 days after the surge with maturation over the following 1 to 3 days. The lifespan of fertile eggs are 2 to 3 days, with the actual fertile period extends from3 to 6 to 7 days after LH surge and increase in progesterone concentration. Vaginal cytologic exams can be used to determine ovulation timing, and ideally progesterone concentrations. LH testing can be used for infertility and frozen breeding. Day zero is the initial progesterone rise and LH surge triggering ovulation. The bitch is most fertile between 2 and 7 days after day zero.
Necessary for breeding;
- Maiden bitches require a veterinary examination for general health, vaginal strictures, and inverted nipples.
- Screening tests for genetic diseases should be discussed.
- A general understanding of the canine estrous cycle, ovulation timing and breeding management should be discussed.
- Stud dogs should be tested annually for Brucella canis.
- Healthy bitches do not need vaginal cultures.
- The veterinarian and staff need an agreement in the case of dystocia.
Conception is mostly likely with natural ties. However, artificial insemination can be highly successful for frozen semen, chilled semen, inexperienced studs or aggressive bitches. During insemination, care must be taken as to not contaminate the semen with other substances. A complete semen analysis from the stud dog should be performed on every collection for motility, morphology and concentration.
- Diestrus follows estrus when the bitch becomes less attractive to male dogs. The vaginal discharge becomes mucoid and diminishes with vulvar edema resolving. Vaginal cytology shows the reappearance of non-cornified cells with vulvar edema slowly resolving. In the absence of pregnancy, diestrus lasts 2 to 3 months.
- After Diestrus, the bitch enters anestrus, a phase characterized by reproductive inactivity, even though hormonal fluctuations are occurring. The uterus is undergoing recovery and the bitch is neither attractive nor attracted to male dogs. The vulva is relatively small. This period usually lasts from 1 to 6 months before the bitch enters proestrus.
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