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This is important information for everyone who choses not to spay their female dog, and don't intend to breed her. I went through pyometra recently, with my 7 year old female. I'd bred her on her two previous heat cycles, and she hadn't taken, and this was probably due to ovarian cysts, as I bred her once at age 3 and then waited too long to breed again. I won't make that mistake twice.
It's important to understand that the dog's reproductive cycle is quite different than us humans- basically their bodies consider themselves pregnant for 63 days following the heat cycle, bred or not, and each "empty" heat cycle increases risk of pyometra.
"The key to understanding reproductive health in dogs is knowing that, as far as a bitch’s body knows, there is no difference between being pregnant and not being pregnant, after a heat cycle.
Those of us (humans, cows, horses, etc.) that cycle on a regular basis prepare our uterus to accept a fertilized egg or eggs every month or so. For a couple of weeks after ovulation we have a higher-than-normal progesterone level, which makes the uterus, which has grown a bunch of soft blood vessels and tissue, keep those vessels and tissue thick and strong so a fertilized egg can land on a lovely spot where there’s lots of blood to suck up and start growing its own little blood vessels.
For humans and other repeated cyclers, when there is no fertilized egg, the body gets the signal very quickly and the ovaries stop producing progesterone and the lining of the uterus breaks down and goes back to normal, at least for another few weeks until ovulation occurs again.
Dogs have a completely different system.
It starts out roughly the same, with the uterus preparing for the eggs by growing a good plush lining, and the eggs ripen on the ovaries and hooray, there’s some lutenizing hormone, and the eggs are released. It gets a little weirder from there, because unlike humans that have fertilizable eggs within a few hours of ovulation dogs’ eggs take two or three days. And unlike humans, whose eggs implant and begin to grow into the blood vessels about a week after ovulation, dogs take about three weeks. But the process is basically analogous.
Where dogs are VERY unlike us is that there is never any signal given to the body that there are in fact no fertilized eggs to nourish, that this has been an unsuccessful heat cycle.
Instead, a dog’s progesterone level stays high for the entire 63 days that she would have been pregnant; her uterus develops the incredibly effective and thick system of blood vessels that would be necessary to nourish an entire full-term litter.
You can honestly say that the only difference between a bitch who was bred and a bitch who was not bred is how many calories she’s burning–either she has to support a litter or she doesn’t–because her body honestly doesn’t know any difference. Aside from some relaxin to loosen her joints (which is present in pregnant dogs but not in non-pregnant ones after the heat cycle is over), the hormone levels are the same.
This would all be just a veterinary curiosity were it not for the fact that the body doesn’t like growing things and then not using them. When the uterus grows this tremendous blood supply, the blood supply actually shapes itself as though there are puppies there. The little attachment sites where the placentas would grow into the uterine lining are shaped differently and have different types of blood vessels. When there are no puppies to fill those shapes, the attachment sites form cysts. After multiple empty heat cycles, much of the uterus can be filled with fluid and cysts. In many bitches, that progresses to infection and pyometra.
The upshot of this whole situation is that bitches are not meant to have empty heat cycles. All else being equal, it is better and safer for them to be pregnant at each heat cycle (or spayed) than it is for them to remain unbred. And diet, panties, and other interventions (or lack thereof) are not the answer – the answer is to use the uterus or lose it....
.....Remember that as far as ANY bitch’s body is concerned, she IS having two litters a year. You don’t do her a favor by having one or both of them be invisible."
(posted with permission to share)
It's important to understand that the dog's reproductive cycle is quite different than us humans- basically their bodies consider themselves pregnant for 63 days following the heat cycle, bred or not, and each "empty" heat cycle increases risk of pyometra.
"The key to understanding reproductive health in dogs is knowing that, as far as a bitch’s body knows, there is no difference between being pregnant and not being pregnant, after a heat cycle.
Those of us (humans, cows, horses, etc.) that cycle on a regular basis prepare our uterus to accept a fertilized egg or eggs every month or so. For a couple of weeks after ovulation we have a higher-than-normal progesterone level, which makes the uterus, which has grown a bunch of soft blood vessels and tissue, keep those vessels and tissue thick and strong so a fertilized egg can land on a lovely spot where there’s lots of blood to suck up and start growing its own little blood vessels.
For humans and other repeated cyclers, when there is no fertilized egg, the body gets the signal very quickly and the ovaries stop producing progesterone and the lining of the uterus breaks down and goes back to normal, at least for another few weeks until ovulation occurs again.
Dogs have a completely different system.
It starts out roughly the same, with the uterus preparing for the eggs by growing a good plush lining, and the eggs ripen on the ovaries and hooray, there’s some lutenizing hormone, and the eggs are released. It gets a little weirder from there, because unlike humans that have fertilizable eggs within a few hours of ovulation dogs’ eggs take two or three days. And unlike humans, whose eggs implant and begin to grow into the blood vessels about a week after ovulation, dogs take about three weeks. But the process is basically analogous.
Where dogs are VERY unlike us is that there is never any signal given to the body that there are in fact no fertilized eggs to nourish, that this has been an unsuccessful heat cycle.
Instead, a dog’s progesterone level stays high for the entire 63 days that she would have been pregnant; her uterus develops the incredibly effective and thick system of blood vessels that would be necessary to nourish an entire full-term litter.
You can honestly say that the only difference between a bitch who was bred and a bitch who was not bred is how many calories she’s burning–either she has to support a litter or she doesn’t–because her body honestly doesn’t know any difference. Aside from some relaxin to loosen her joints (which is present in pregnant dogs but not in non-pregnant ones after the heat cycle is over), the hormone levels are the same.
This would all be just a veterinary curiosity were it not for the fact that the body doesn’t like growing things and then not using them. When the uterus grows this tremendous blood supply, the blood supply actually shapes itself as though there are puppies there. The little attachment sites where the placentas would grow into the uterine lining are shaped differently and have different types of blood vessels. When there are no puppies to fill those shapes, the attachment sites form cysts. After multiple empty heat cycles, much of the uterus can be filled with fluid and cysts. In many bitches, that progresses to infection and pyometra.
The upshot of this whole situation is that bitches are not meant to have empty heat cycles. All else being equal, it is better and safer for them to be pregnant at each heat cycle (or spayed) than it is for them to remain unbred. And diet, panties, and other interventions (or lack thereof) are not the answer – the answer is to use the uterus or lose it....
.....Remember that as far as ANY bitch’s body is concerned, she IS having two litters a year. You don’t do her a favor by having one or both of them be invisible."
(posted with permission to share)
