How does a dog's heat end? - briefly
A dog's heat ends when progesterone levels decline, signaling the conclusion of the estrous cycle. This typically occurs about 14 days after ovulation, marking the start of the next heat cycle in approximately six months.
How does a dog's heat end? - in detail
A dog's heat, or estrus cycle, is a complex process regulated by hormonal changes. The end of a dog's heat can be determined by several key factors and usually occurs in two distinct phases: the follicular phase and the luteal phase.
During the follicular phase, which lasts approximately 9 days, follicle-stimulating hormone (FSH) stimulates the growth of ovarian follicles containing immature eggs. As these follicles develop, they secrete estrogen, which prepares the dog's body for potential pregnancy by thickening the uterine lining and causing behavioral changes such as increased mounting and nesting.
The luteal phase follows, lasting about 9 days, during which the dominant follicle ruptures, releasing the mature egg into the oviduct—a process known as ovulation. Simultaneously, the remaining follicular tissue transforms into a temporary structure called the corpus luteum, which secretes progesterone. Progesterone maintains the uterine lining and inhibits further follicle growth, effectively ending the dog's heat until the next cycle.
If mating has not occurred during the estrus period, the corpus luteum begins to degenerate approximately 2-4 days after ovulation. This decline in progesterone levels signals the end of the heat cycle and triggers a new follicular phase, leading to the next estrus cycle.
However, if successful mating has occurred, the corpus luteum persists throughout pregnancy, continuously secreting progesterone to sustain the uterine lining and prevent further ovulation until parturition or pseudopregnancy (if the dog is not pregnant). In this case, the end of a dog's heat is marked by successful mating and the establishment of pregnancy.
Additionally, some dogs may experience false pregnancies or anestrus periods due to hormonal imbalances or other health issues. These conditions can alter the typical 3-4 month estrus cycle duration and should be evaluated by a veterinarian.
In summary, the end of a dog's heat is signaled by the degeneration of the corpus luteum and the subsequent decline in progesterone levels if mating did not occur. If mating was successful, the heat ends with the establishment of pregnancy. Understanding these hormonal changes is crucial for monitoring a dog's reproductive health and ensuring responsible pet ownership.