syncronized heat - Page 1

I have 2 bitches, 1 is 5 the other is 23 months. The 5 year old was spayed 6 months ago. the 23 month old was always comming into heat 1 week after the 5 year old. younger ga was ike clock work since 6 months old. Now, she has not come into heat. She was due in heat in June. Any comments would be appreciated.

She has been to the vet and has passed her exam including a swab for uterine infestion.

Hasanyone had a similar situation?

Its very possible that since now your 5yr old will not have heats any longer, it will throw off the cycle of your younger female. 

There is limited research on what may cause menstrual synchrony, but the most common hypothesis has to do with pheromones–airborne, odorless, chemical signals produced by the skin, which animals use to share information about sex and reproduction.

23 months is still young. Her heat cycle isn't necessarily set in stone and yes the older bitch was probably "pulling" her in.  Has it been real hot or has she had some other stressor in her life? That can change heat cycles. My bitch is usally pretty darn regular but a couple years ago we were having one heck of a heat wave (30days over 100) and her cycle got delayed by almost 2 months. My vet was not at all worried - she also had a clean bill of health - he viewed it as a strong reproductive trait that basically the body understood that in the wild this would be a very very bad time to have pups(lack of food from drought) so even tho that's not the case in our civilized world with pet food stores - her body was still reacting on a very primitive level. Perhaps something like this goes on.

Years ago I had another bitch who lived with her mother and had very regular heats but was not bred for a number of heats. She  did not exhibit much in terms of breeding behavior (flaggin etc) UNTIL AFTER her mother was spayed.  Again very much like the wolf pack where only the dominant alpha bitch actually gets to breed.  So there is a lot going on that's not necessarily visible to our limited senses.