Estrus Cycle in Dogs

                     Estrous cycle in dogs start when the dog attains to the age of puberty.

Normally, the average age of puberty is about 6 months but varies from breed to breed. Smaller breeds attains at the earliest age than large and gaint breeds.

                    Most of the dogs come to heat twice a year or 6 months interval although vary from breed to breed and other conditions of animal ( disease, obesity etc). It takes upto 2years of age for attaining regular cycles. There is no time in a year for domesticated animals except breeds like basenji, tibetan mastiffs which typically tend to cycle in the spring. 

Stages :

1. Proestrus
2. Estrus
3. Diestrus 
4. Anestrus 

In orderly manner. 

Proestrus:

           During this period one or several follicles of the ovary starts to grow. Their number is species specific. This phase lasts for 1 day to as long as several weeks. During this phase under the influence of estrogen the corpus luteum of previous cycle regress and the endometrium of uterus starts to develop. Some bloody discharges can be seen at this age though the animal is not yet sexually receptive.

Behaviour :

                Due to rapid follicular growth and estrogen levels results in swelling of vulva, congestion of reproductive tract and bloody vaginal discharges and animal becomes restless. The female will begin to play bow and show submissive behaviour towards male. In some conditions the female will be aggressive towards male. On an average this period lasts for 9 days.

Estrus phase : 

              The ovulation LH surge occurs within minutes of copulation and reaches base level within 14-16 hours. Of ovulation not induced during estrus phase the female enters into anovulation phase and go into prostrus again. If the mated female ovulates diestrus ensures which can proceeds to gestation.

Behaviour :

             Females are in estrus for 3-14 days during which they will show clear behaviour of mating like calling, rolling, urinating etc.

Female assues a lordosis behaviour with head and forelegs down, rump held high during mating. Estrus is characterised by permitting male mounting, coitus and usually vocalisation, lordosis and foot treading. Behaviour signs and strongest in association with peak estrogen surge by 3rd day of estrus.

Diestrus :

              During this phase the female no longer displays estral postures and is unresponsive to male. CL develop as raised reddish orange structures with poygonal cellular morphology each reaching maximal size within 15-16 days. Circulating progesterone increases above baseline approx 76 hours after mating. This stage lasts for 2 months. Estrogen levels are low, while progesterone peaks 3-4 weeks after the start of diestrus and declines to baselevel by the end of  diestrus period. This increase and decrease of progesterone levels will occurs regardless of if the dog is pregnant.

Anestrus: 

           It is the stage between diestrus and next pro-estrus. This stage lasts for about 4 months, though certain breeds can be much longer. There will be no external signs during this period. The body uses this time to allow the uterus to prepare for the next possible pregnancy.

                                Canine estrus cycle is a complex interaction of hormonal, physical and behavioural changes.

          Any doubts regarding estrus cycle please feel free to comment or contact on youcanmaildoctor@gmail.com