1 - Mammary development and lactation – to relieve the discomfort and pain caused by pressure in the mammary glands, bitches often lick or suckle this area.  This stimulates oxytocinhormone produced by the hypothalamus in the brain that stimulates milk let-down production, increases 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. production and thereby maintains lactation.

2 - Behavioural changes - This is associated with an increased maternal instinct, which often manifests itself as searching for and mothering toys/ cushions etc. and nest building.  She may spend a lot of time in her sleeping area and this may progress to nest building and guarding. Occasionally bitches may be aggressive, especially to strangers.

 
3 - There is often a change in appetite, either a reduction or an increase.  Vomiting may also be observed.

 
4 - Weight gain and a swollen abdomen are also commonly observed

Diagnosis

Many of the above clinical signs are similar to those observed during late pregnancy.  It is therefore essential to exclude pregnancy before considering treatment.  Pyometrainfection and pus accumulation within the uterus can also cause changes in appetite and behavioural changes and occurs at same stage of oestrus.  Ultrasound is a good way of diagnosing both pregnancy and Pyometrainfection and pus accumulation within the uterus.