Here is a breakdown of the different stages of the estrous cycle in golden retrievers:
* Proestrus: This is the first stage of the estrous cycle and it usually lasts for 3-10 days. During this stage, the ovaries prepare to release an egg. You may notice some spotting or bleeding from the vulva.
* Estrus: This is the second stage of the estrous cycle and it usually lasts for 5-8 days. During this stage, the egg is released from the ovary and travels down the fallopian tube. The bitch will be fertile during this time. You may notice that her vulva is swollen and she may be more attracted to male dogs.
* Diestrus: This is the third stage of the estrous cycle and it usually lasts for 60-90 days. During this stage, the corpus luteum (a gland that forms on the ovary after the egg is released) produces progesterone. This hormone helps to prepare the uterus for pregnancy. You may notice that her vulva returns to its normal size and she is no longer interested in male dogs.
* Anestrus: This is the fourth and final stage of the estrous cycle and it usually lasts for 4-6 months. During this stage, the reproductive system is inactive.
The estrous cycle in golden retrievers typically repeats itself every 6-12 months. However, this can vary from dog to dog.