Reading Vaginal Smears to Determine When to Breed Your Bitch
"Becoming a "DOG BREEDER" means having the courage to stick with the dogs of your bloodline (because they work) and not getting side tracked into popular fads, and yet still having the common sense to admit when you made a mistake in selecting breeding partners."
Being able to perform and read vaginal smears at your kennel is going to greatly improve your success rate in getting bitches bred. The vaginal smear is not perfect but its sure better than guessing what day a bitch should be bred on.
In recent years we have seen a lot of publicity on progesterone testing of a bitches blood to determine the exact day to breed. Some of these tests (I will not name names) are useless and a total waste of money. Others are expensive and require blood to be sent in to a lab to test. This may take days and can be time prohibitive. The concept is a good but until our local vets can perform tests in their office and give us on the spot test results they are not that functional for the average dog breeder.
Outside of a good old stud dog, the best method available to determine when to breed a bitch remains the vaginal smear.
Many breeders don't use it because they believe it's difficult and don't understand how simple it is to read. This article is meant to help correct this situation.
A number of years ago my vet (Dr. John Flynn in Eau Claire WI) gave me a chart put out by the Ralston Purina Company. I doubt that Purina still offers it. I tried to get another and could not. This chart showed pictures of vaginal smear slides from different times during a bitch's cycle. It was extremely helpful teaching me how to interpret an individual slide. The photos in this article are from that Purina publication.
In medical terms a bitch goes through 4 different stages:
Proestrus begins when the bitch swells and begins to drop blood. It typically can last from 4 to 20 days. During this period a bitch may attract males but will not accept them for breeding.
Estrus is the time a bitch can be bred. This can last from 4 to 13 days. Typical this is the 9th to the 12th day of a bitch's season. But I have seen bitches bred as late as the 26th day of season. Determining estrus is critical in determining when to breed (either naturally or with artificial insemination).
Metestrus is the period after estrus and can last 80 to 90 days. During this period the bitch will not accept a male.
This period represents the quiet phase of the bitch's estrus cycle. It lasts 2 to 3 months after metestrus. During this time period the female is not swollen and will not allow breeding.
Doing vaginal smears requires a good microscope. We bought our scope used from a local vet. With that said there are companies that sell and repair micrscopes who often have used scopes. The one in our area is Midwest Microscope Service 800-605-3065
Determining the first day of a bitch's season (that
point where she starts to bleed) is important. If you have not bred a
bitch before its good to know that most bitches will blow their coat just
before coming into season. This can be anywhere from 3 weeks before she
begins to bleed to the week of proestrus. I try and educate the foster
parents of my bitches to watch for this sign. When they begin to see the
bitches shedding, its time to do a visual inspection each morning before
the dogs go out side.
The problem is that many females will clean themselves
through licking for several days before the blood is actually noticed.
It's a good idea to establish a base line of slides
during proestrus. By starting on the 5th or 6th day and then doing smears
every day or every other day you will be able to notice significant changes
in the cell structures.
When I try and explain what to look for to new employees,
I tell them that during proestrus the slide has little dark dots and fried
eggs. The dark dots are red blood cells. The fried eggs are the epithelial
cells. During proestrus there are a lot of the red blood cells and the
epithelial cells are nice and round with dark round centers. (See the
What we want to watch is the changes to
the epithelial cells. As a bitch moves through proestrus there will be
a reduced number of red blood cells and the epithelial cells will begin
to look like potato chips. The centers will disappear and the edges of
the cells will begin to get rough (the vets call these cells cornified
epithelial cells.) This is when the bitch is approaching estrus. When
I notice this change I will do daily slides.
During the early days of proestrus the female will initially
not allow the male to mount her, but as she nears the end she will flag
and allow the male to mount but she will not allow penetration. When I
see this I know I am within a day or so of breeding the female.
Estrus normally occurs 8 to 11 days after a bitch starts
to discharge. It lasts 4 to 13 days and during this time the female can
be bred. During this time a visual exam will indicate swelling of the
vagina area and noticeably less blood in the discharge.
When the slides are examined there is a noticeable difference
between proestrus and estrus. During estrus there are very few (if any)
red blood cells (erythrocytes). There will be a dramatic increase in the
cornified epithelial cells. They will often be stuck together in chunks
(but this can vary because of the way that you manually roll the cells
on to the slide.) You can see what this look like in the photo below.
On normal bitches this is the time to start to breed
naturally or do an A.I. (artificial insemination). How often and when
to breed is something I have found to be controversial among vets. I
have been told (by well respected vets who specialize in breeding dogs)
if I own the stud dog I should breed her every day that she will stand.
On the other hand there is a lot of published information that indicated
breeding 2 times 2 days apart is all that is necessary.
What I will do is collect a male and examine his sperm.
If the male is young, healthy and full of sperm breeding one or two times
is all that's necessary (on a natural breeding sperm can live 4 days
in the bitch - less of A.I.'s). As the stud ages and there is noticeably
less sperm it may be a better idea to breed more often. I will also collect
a male several days in a row and watch how this effects the dogs sperm
production. If a dog can continue to produce enough healthy sperm you
will know if he is capable of breeding 2 females on alternate days. When
you collect sperm its a good idea to warm the slide to body temperature
(101 degrees) before depositing the sperm to be examined. You will have
a better idea of the mobility of the sperm that way rather than put them
on a cold slide.
Collecting males is a subject of its own article.
During this period the bitch will quit flagging and
will not breed anymore. There is a noticeable lack of interest in being
friendly to males. This period represents the "leuteral" or
regressive stage of a bitch's season.
Once again this period lasts 80 to 90 days. During the
first 2 or 3 days there is a noticeable lack of cornified epithelial cells.
During the first 3 or 4 weeks there is an increased number of leukocytes.
As this period progresses you will begin to see non-cornified epithelial
cells again (the fried eggs.)
This period lasts 2 or 3 months and during this time
there are very few cells noticeable if a slide is taken. The photo below
is an example of what you would typically see.
DETERMINING IF THE BITCH IS PREGNANT
Once you have bred the bitch it is very helpful to know
if the breeding took. Until recently (at least in my area) this has been
difficult. If a female is a large bitch with a small (one or 2 babies)
litter the breeder would often not know she was pregnant until the puppies
A vet in my area recently started using a blood test
called "Fibrinogen Assay". If blood is draw on a female before
a breeding and then 30 days after the breeding. The vet can tell you if
the bitch is pregnant. I am told that is 100% accurate.
I am told that a "Fibrinogen Assay" can even
be used if blood is not drawn before the bitch is bred. When this happens
the degree of accuracy goes down a little.