The heat cycles of the bitch are caused by hormones that are produced and released by the ovaries. As soon as the dog has grown enough it goes in to heat the small breeds, heat cycles occur at five months old, while in the Bigger dogs, this may not occur until the animal is fourteen to eighteen months old. these cycles will occur every six to nine months throughout the life of the animal.
The heat also known estrus cycle of the bitch is divided into four different stages. There is variation in the length of these cycles among come of the breeds and among various different breeds.
The first stage of a heat cycle is a preparatory period known to as proestrus. Proestrus typically lasts five to nine days. On the first day of proestrus, the vagina