Female dogs have their first estrus cycle -- known as coming on heat or being in season -- at around 6 to 7 months, though it can be as early as 4 months or as late as 2 years in some breeds and individuals. From then on, most bitches come on heat twice a year. During estrus, female dogs have a blood-stained discharge.
The first stage of estrus is pro-estrus, lasting 4 to 15 days, and a hormone called estrogen is produced causing changes in the bitches' wombs and vaginas in preparation for mating. Blood vessels in their wombs become enlarged, and red blood cells seep out of some vessels causing blood-stained discharges. The amount of discharge varies, with some bitches only spotting, while others bleed heavily. The blood loss can be deceptive, depending how frequently females lick themselves clean.
The is followed by estrus proper, lasting 4 to 8 days, when ovulation -- where the eggs are released from the ovaries -- takes place, females become receptive to male dogs and the bloody discharge usually reduces and eventually stops.
The blood stains on furniture and carpets can be soaked with cold, salted water and washed with biological washing powders to clean them.
Dog knickers with sanitary pads can help to prevent staining indoors. They can be bought from pet stores or homemade. Coming on heat can be prevented by spaying female dogs. Consult your veterinarian to discuss spaying or any concerns with estrus.
- Doglopaedia A Complete Guide To Dog Care; J. M. Evans and Kay White
- Caring For Your Dog; Dr. Bruce Fogle
- Veterinary Notes For Dog Owners; Trevor Turner B.Vet. Med., M.R.C.V.S.
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