The Reproductive Cycle

The cycle of female dogs is said to be non-seasonal, i.e. they can come on heat at any time during the year, and this usually happens every 6-7 months. The cycle is divided into four stages: Pro-oestrus and Oestrus, which involve the hormone oestrogena steroid hormone produced primarily by the ovaries that stimulates changes in the female reproductive organs during the oestrous cycle and promotes the development of secondary sexual characteristics., Metoestrus, which involves the hormones progesteronea steroid hormone secreted by the corpus luteum of the ovary that maintains pregnancy and promotes the development of the mammary glands. and prolactina hormone released from the anterior lobe of the pituitary gland that stimulates the secretion of progesterone by the corpus luteum and initiates and maintains lactation. and Anoestrus, a quiet period with no hormonal influence.

The Reproductive Cycle

Pro-oestrus

associated with vulval oedemafluid accumulation/ swelling and a blood tinged vaginal discharge
she will attract the male but will not stand to mate
lasts around 7 - 10 days

Oestrus

she will accept the male and stand to mate
ovulationthe release of an egg cell (ovum) from the ovary in female animals occurs 2 days into the cycle whether she is mated or not
lasts around 7 - 10 days

Metoestrus

lasts around 90 days
associated with two hormones:

Progesteronea steroid hormone secreted by the corpus luteum of the ovary that maintains pregnancy and promotes the development of the mammary glands. - maintains pregnancy
Prolactina hormone released from the anterior lobe of the pituitary gland that stimulates the secretion of progesterone by the corpus luteum and initiates and maintains lactation. - causes milk production and nursing behaviour in late pregnancy, in preparation for the arrival of puppies

interestingly, however, high levels of progesteronea steroid hormone secreted by the corpus luteum of the ovary that maintains pregnancy and promotes the development of the mammary glands. and prolactina hormone released from the anterior lobe of the pituitary gland that stimulates the secretion of progesterone by the corpus luteum and initiates and maintains lactation. are still produced even if she is not pregnant and it is these high levels of prolactina hormone released from the anterior lobe of the pituitary gland that stimulates the secretion of progesterone by the corpus luteum and initiates and maintains lactation. that are responsible for causing false pregnancy

Anoestrous

variable length (usually around 4-5 months)
during this stage progesteronea steroid hormone secreted by the corpus luteum of the ovary that maintains pregnancy and promotes the development of the mammary glands., oestrogena steroid hormone produced primarily by the ovaries that stimulates changes in the female reproductive organs during the oestrous cycle and promotes the development of secondary sexual characteristics. and prolactina hormone released from the anterior lobe of the pituitary gland that stimulates the secretion of progesterone by the corpus luteum and initiates and maintains lactation. levels decrease to baseline values