Understanding Dog Estrus Cycle: Tips & Precautions
Typically, the interval between the onset of the first estrus and the next estrus is referred to as the estrous cycle. The estrous cycle in bitches is notably longer, stretching up to ten times the duration of domestic animals. Approximately 65.2% of bitches experience two estrous cycles annually, with an average interval of 182.4 days (ranging from 156.7 to 219 days). For 26.1% of dogs, there is a single estrous cycle per year, while 8.7% of canines have three estrous cycles in a year. The duration of these cycles can vary significantly among different breeds, ranging from 22 to 47 weeks, with an average of 31 weeks.
During the estrous cycle, under the influence of the nervous and hormonal systems, the bitch's overall condition and reproductive organs undergo a series of intricate changes. Based on these transformations, the estrous cycle can be divided into four distinct phases: the proestrus, estrus, metestrus, and anestrus.
The proestrus phase lasts an average of 9 days (ranging from 3 to 16 days). It commences with the appearance of vulvar swelling and pale vaginal discharge, and concludes with the acceptance of mating by a male dog.
The estrus phase, which lasts for approximately 9 days (4 to 12 days), is quite similar to the proestrus phase. It spans from the first day of mating to the last, with the estrus phase in young dogs often being longer than the average.
The metestrus phase lasts an average of 75 days (60 to 90 days). This period begins after the last mating and continues until the corpus luteum regresses. During this time, vulvar swelling diminishes and gradually returns to normal, the bitch's temperament becomes calmer, and her interest in males wanes. She becomes less receptive to males and may even resist their advances. After about 2 to 3 months, she enters the anestrus phase. If she becomes pregnant, she will then move into the pregnancy phase.
The anestrus phase is characterized by a period of reproductive inactivity. After several months of anestrus, the cycle repeats with the onset of the next proestrus phase.
