Cats and Dogs

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Introduction to basic information about the heat cycle, pregnancy, and delivery in dogs and cats.

Below are links to other topics related to sex and reproduction in cats and dogs.

Reproductive Topics
On Other Pages:

Whelping or Delivering Puppies

Alternatives to Spaying and castration for birth control

Newborn Care for Puppies and Kittens

Momma Dogs who won't nurse.  Agalactia (no milk) 

Mastitis (infection of the mammary glands)

Pyometra (infection of the uterus)

False Pregnancy

Undescended Testicles

Brucellosis This disease causes abortions.  This serious disease is also contagious to humans and other mammals.

Reproductive Surgery:

Spays (Ovariohysterectomies) in Dogs, Cats, and Other Pets

C Sections
Includes an interesting short history about a women doctor pretending to be a man performing the first modern C Section

Castration in Dogs, Cats, and Other Pets.  Includes recipes for Rocky Mountain Oysters, Montana Tendergroins, and Swinging Beef.  What Viagra is made from.

Reproduction in Dogs
Introductory Comments

Dogs are a little like humans when it comes to sex... males are willing any time, any place, but the females only "want to" when it suits them.

The Canine "heat" cycle:
Sexually mature female dogs have an estrus cycle or heat...that period of time when they ovulate, are receptive to male dogs, and can get pregnant...commonly every 5-12 months. The average is every 7 months, but it's quite variable.

This period known as being in heat lasts about 3 weeks, but that too, is just an average. For practical reasons we divide the heat into 3 parts, each part lasting, on average, about 1 week:

Week 1: (Proestrus) The female vulva swells and secretes blood and aromas that drive males into frenzies and on a humid night will attract them from miles around. I'm not sure whether the smell travels so far or whether there's a communication system of jungle drums at work. The female may act moody during this stage to both people and other dogs, swinging from affectionate to "snappy" and seem to like to "tease" the males cruelly: they'll lift their tail to allow a sniff, but will bite the male's head off if he tries to mount.

Week 2: (Estrus) During this week, where the female is in true estrus, her vulva will still be swollen, but her vaginal discharge will usually stop having visible blood in it, she will ovulate, and will usually let the male...often any and all males... mount her. And assuming no underlying problems, she will probably become pregnant. Possibly from multiple males; in other words, each puppy in the litter could have a different daddy.
This period, while on average, about a week long, can be much shorter or longer.
Things can go wrong; see below.

Week 3: (diestrus) During the last stage of being in heat, the female has already ovulated and is losing interest in sex, but the male(s) will still be determined. She is not likely to allow mounting and if forced to breed is not as likely to get pregnant.

"The Tie": Unlike cat sex, which is a wham bam deal, dogs take their time, and once a male successfully penetrates the female (in an inexperienced male this may take some time or even some guidence from a human) there is a bulbous gland at the base of the penis that swells locking it into the vagina. To get more comfortable, the male will usually do a little dance step over the rump of the female and end up facing away from her...this is called the "tie" and naturally lasts about 3-20 minutes. Both the male and female will often have a goofy look on their faces.

If you catch a pair of dogs in a tie, you can cause injury to both the male and female genitals and probably get bitten besides, if you try to pull them apart. Drenching the pair with cold water usually works, but alas, it's probably too late to prevent an unwanted pregnancy.

Lots of things can go wrong.  These include cystic ovaries, "false pregnancy", inability to give birth, dead puppies, not having milk, infected mammary glands,  and all manner of other female problems.

Infections of the uterus (especially after abortions or birth), are not uncommon. Uterine infections are very serious.

There is a reproductive disease that is especially important called canine brucellosis...there aren't usually any symptoms in the adult dogs, but if either of the dogs are positive for this sexually transmitted disease, there is a higher chance of infertility or abortion. Serious breeders require that both the male and female be tested first by your veterinarian.  I discuss many of the problems inherent with reproduction on other pages... the links are to your left.

Misc Comments:

About spaying your dog (or cat) while in heat:
We can spay your dog if she's in heat, but we should really try to avoid it. It's more dangerous and it usually costs more. The hormones of heat (estrogen) retard clotting and healing. And the uterus and ovaries are larger, full of throbbing blood vessels, and are very fragile (easily torn) when in heat.  Expensive post op care and possible death are much more likely if your dog is spayed while in heat. Plan Ahead!

Breeding Tips
Take the female to the male's territory (house) if possible...the male will be more emotionally secure.

Do you believe this? Males insecure?
Well, yes, it turns out some males, especially if inexperienced, are a little unsure of themselves in the presence of a demanding female.

Put the female in with the male starting the second week. If they breed within an hour or so, fine, record the date as first breeding. If they don't breed, return in one to two days and try again. For maximum chances of getting pregnant, allow at least 2 breedings.

If they refuse to breed, consider another male, or if the female is bulking, consider a visit to the vet to confirm what stage of estrus she's in. She may need a mild sedative or restraint. Or she may have a more serious problem. Or it could easily be that it's the male who has the problem. It seems like the more you want a successful breeding the more likely something will screw it up.

If the breeding of 2 particular dogs is of great importance to you and there have been previous problems with either of the partners, veterinarians specializing in reproduction are probably even more experienced than their human physician counterparts...  talk to your local vet about a referral if appropriate.

"False Pregnancy"
Many people (including vets) are fooled by false pregnancy: Many females produce so much progesterone (also known as the hormone of pregnancy) after being in heat that they look and act pregnant. They bloat out and swell. They make nests. They sometimes leak milk. But come day 62 or so, no babies, their milk dries up and they go back to normal. Usually.  I discuss this interesting problem on another page.  The link is in the column to your left.

Some comments about pregnancy in dogs:

Once a female is bred, her period of pregnancy is normally 62 days give or take 5 days.

Lots can go wrong during this time.

Fevers, poor nutrition, stress, viral infections, dehydratrion, brucellosis, heat stress, and bacterial infections are all possible causes of abortions and miscarraiges.

Parasites are especially stressful and more likely to be a problem too, since the hormones of pregnancy suppress a female's immune system and resistance.

And while it's more important than ever to control worms and fleas etc when a dog is pregnant, you also have to be more careful about which chemicals are safe. Don't dink around...ask your vet.

Testing for pregnancy

By Palpation:  very difficult to palpate fetuses until day 25 and even then it's easy to be mistaken.

By blood test:  There is a fairly new blood test for detecting pregnancy in dogs but it's not too accurate until the 2nd month of pregnancy.

By Ultrasound:  This is presently the best method in that we can often detect embryo's or fetuses as early as day 14.  But fairly expensive.

By radiography:  The little bones in the fetuses don't calcify enough to see on radiographs until about day 42. 

Reproduction in Cats
Introductory Comments

Feline Reproduction is very similar to canine reproduction in these ways:

1.  pregnancy lasts about 62 days plus or minus 5

2.  cats are prone to all the same potential medical problems during and after pregnancy as dogs.

3.  we can't tell with much accuracy that cats are pregnant by ultra sound until at least day 14, by palpation until at least day 25, and by radiographs until day 42

But Feline Reproduction is different from canine reproduction too:

1.  Cats can go into heat at any time of year, just like dogs, BUT are much more likely to go into heat in the Spring, Summer, and early Fall as they are influenced by the length of daylight.

2.  Cats will stay in heat about 5-15 days ... but unlike dogs will keep going back into heat every 1-3 weeks until they ovulate.... and cats are unlikely to ovulate until there is penetration.  (simulating penetration will usually stop your cat from cycling BUT without anesthesia your cat will bite and scratch the tar out of you.)


This first stage of heat lasts 1-3 days. You might notice that the vulva is slightly swollen.  She will probably have the "munchies", be more affectionate in general, and meow more.

Males will be attracted and "court" the female but she will likely play "hard to get".
She may urine mark around the house.

Estrus (Heat)

This lasts about 4-6 days. Cats in heat make more noise and her meows are louder and more frequent-eventually becoming almost constant.  She becomes much more affectionate toward people, weaves in and out of their legs, rubs against them, shakes her pelvis, and rolls about on the floor, and "flags" her tail. If picked up when rolling, she may grab at your arm or even bite.

Website Directory

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"What To Expect When You Go To The Vet"
if your pet should have a problem with ...

Abscesses, wounds, and injuries

Arthritis, Lameness, Fractures, and Ligament Injuries
To include Femoral Head Removal, Hip Dysplasia, Anterior Cruciate Ligament Injuries, Panosteitis, Radiographic Demonstrations, Disc Disease, and Bone Surgery

Bladder, Urinary Tract, & Kidney Problems

Blood Diseases, Anemias etc
Strokes, Vascular Diseases, Anemias, DVT, DIC, Blood Parasites, Rat Poison, & Bleeding disorders

Cancer, Masses, Lumps and Bumps

Cardiology  Heart disease in Cats, Cardiac Hypertrophy, Valvular disease, Cardiac Insufficiency, Congestive Heart Failure, Heartworm Disease, and a little history about the milestones in treating heart disease

Cats: general information page and directory of diseases and problems specific to cats including vaccine recommendations, leukemia, feline viral infections, feline upper respiratory disease and cats that just aren't feeling well.

Dentistry and problems of the mouth and throat

Dermatology: Skin problems including allergies, rashes, bacterial infections, and itching. Hair Loss, Yeast Infections, Hormonal Problems


Ear Infections and Other Ear Problems

Eye Problems  and Ophthalmic Diseases

Exotics:  Pocket Pets, Rabbits, Hamsters etc

Fleas, Ticks, and other parasite problems

Heart disease; Cardiac diseases, vascular diseases, stroke, & heartworms

Hormone Diseases: Diabetes, Thyroid Disease, Cushing's Disease or Hypercortisolism, Addison's disease or Hypocortisolism, Pancreatitis, obesity as a disease

Infectious Diseases  Colds, Distemper, Parvo, Leptospirosis, Bruceellosis, Panleukopenia, Feline AIDS, Leukemia, Hepatitis, Kennel Cough, Ringworm, Rabies, FIP, Canine Herpes, Toxic Shock Syndrome, & More

Intestinal problems: diarrhea, constipation, torsion, indigestion, and gas. Also pancreatitis, vomiting, esophagitis, colitis, parvo and other types of dysentery

Kidney Disease

Liver Diseases     

Metabolic Diseases: Diabetes, Thyroid Disease, Cushing's Disease or Hypercortisolism, Addison's disease or Hypocortisolism, Pancreatitis, obesity as a disease

Neural Problems and Diseases: Epilepsy, Rabies, Distemper, FIP, Paralysis, Tetanus, Seizures, Disc Disease, Toxoplasmosis & others

Obesity; new information and about Pfizer's new FDA approved treatment


Parasite Problems; Fleas, Ticks, Heartworms, Intestinal Worms, Mosquitos, Lice, Mites, and other welfare recipients

Poisons  Snakes, Insects, household chemicals, plants, and foods that might poison your pet

Respiratory Diseases

Senior Pet Page: Geriatric Medicine

Skeletal-Muscular Problems Arthritis, Fractures, ACL, Ligament Injuries, Disc Disease, Pannus, and many other problems of the bones, muscles, tendons, and ligaments

Skin Problems: allergies, rashes, bacterial infections, and itching. Hair Loss, Yeast Infections, Hormonal Problems

Surgery: Spays, Castrations, Testicle Recipes, Soft Tissue Surgery, Hard Tissue Surgery (Bones), C- Sections, Declawing, Tumor Removal and Cancer Surgery

Wounds, punctures, injuries, and abscesses

Urinary Tract Diseases and Problems

Other Topics on This Site

The Human-Animal Bond

History of Veterinary Medicine; lots of interesting stuff    

Zoonotics: Diseases, worms, and parasites people get from pets.

Lab Tests and what they tell us

Medications/Pharmacy Page

Nutrition & Diets
Includes information about Prescription diets used to treat disease, and a discussion about the pet food industry

Reproduction, breeding, & rearing information
Includes information about feline and canine heat or estrus, breeding, C-Sections, pyometra or Infected Uterus, dystocia, no milk, mastitis, & brucellosis
Also newborn care, undescended testicles, and alternative to spaying and castration

Vaccine and other preventive health recommendations

WildLife Page:  Taking care of baby bunnies, squirrels, and birds.  A very funny story about beavers, and other misc information

Our Dog Page:  a directory of problems of concern in dogs including parvovirus, distemper, canine herpes, and other diseases

Veterinary Pet Insurance