[BLOG] Estrus Induction : Yes We Can in Canines

This blog was first published in Aug 2017. I edited and re-published it in Jan 2020.

As I write those lines, I’m currently on a plane.

Somewhere above Africa. On my way to Johannesburg. 

You’ll never know when inspiration strikes… and when it does… well, you’d better get on it, right ? 

” I’ve never seen her in season, Doc. Anything we can do about that ?” 

That is a discussion I had a long time ago with a dog breeder client. 

She was breeding Yorkies. 

And for one of her bitch, she was never able to detect when/if she was in season.

Silent heats… or not ? 

She thought she was dealing with what she called “ghost heats”. 

This is a term I heard quite often over the years ; it refers to the fact that the bitch might be in season, but you simply don’t see it. 

No vaginal blood discharge, no vulvar swelling, no change in behaviour… 

Even if you have male dogs around, often they do not detect anything and definitely don’t look interested by the female…

In veterinary medicine, we usually use the term “silent heats”.

I already woite on this topic, see my previous blogs here :

The truth about Silent Heats Part I

The truth about Silent Heats Part II

And in this case, that could definitely be the case indeed !

After all, my client was breeding Yorkies, and in my experience, silent heats are more often encountered in small breeds.

That being said, let’s be fair: it can happen in any breed. 

So my Yorkie breeder was wondering : was there a way for her to deal with this ? 

Obviously, I had a few options in mind ! 

Step 1 : Confirm there is no underlying medical condition

In a case like this, we would always start by making sure there is no underlying medical condition that could explain the situation. 

It starts by a physical exam, to confirm there is nothing wrong. Some congenital malformations can indeed prevent the bitch from coming into season (in cases like hermaphrodism for instance) or expressing clinical signs that the animal is actually in season  (persistence of the hymen for instance – which normally breaks during puppyhood, but if it does not, you might then not know when the bitch is in season).

It then continues with a hormonal assay. We will typically look at the progesterone blood levels, because if there is progesterone that is secreted it can definitely confirm the bitch might have undergone a silent heat (progesterone is only secreted AFTER ovulation). 

We will also perform a genital ultrasounds, to check if there is no abnormalities on the ovaries (ovarian cysts, which can definitely prevent the bitch from being in season) and/or uterus (not directly related to the situation but before to attempt any treatment, we want to make sure there is nothing wrong there). 

These are what I consider the essential steps, each case being different the attending veterinarian might definitely adapt a different approach based on the animal seen in consultation. 

The goal is however always the same : before attempting anything, we want to make sure there is no hormonal activity (that is why we assay progesterone) and that there is no underlying medical condition, which is obviously a contra-indication to trying anything here (we must attend first the medical condition then). 

And if everything looks normal.. there is therefore no contra-indication to try what we call “estrus induction”. 

We did all of this in this case. We found nothing abnormal. 

We could then move to the second step : discussing how to induce the bitch in season. 

Estrus Induction: How ? 

Estrus induction = medical protocol to initiate the bitch’s season. 

Yes. We can do that in veterinary medicine. 

We can do it in dogs and, when used properly, it is actually quite efficient. 

If you ever go and look in the veterinary scientific literature, you will see that there are 3 main types of medical protocols that are used for this :

– The older ones rely on molecules we call gonadotrophins ; they are actually adapted from protocols that were developed in large animals (cows, pigs). They are very easy to use (those molecules usually come as injectables) but unfortunately the fertility results are VERY low… Canines indeed are very specific in terms of reproductive physiology and they definitely do NOT respond as well as large animals with those molecules ; in our clinic, this was definitely not the option we would go for in terms of estrus induction ; 

– Other protocols use what we call dopamine-agonists (the main molecule in this regard is called cabergoline) ; protocols were published in the 90s and showed that those molecules were actually a very good option to consider when it comes to estrus induction in canines ; they good be given orally (so super simple to use) and the fertility results were excellent ; today this is definitely an option worth considering ;

– The most recent protocols rely on the use of GnRH-agonist implants ; the results are very similar to what we can obtain with cabergoline ; it is definitely more technical (the implant needs to be administered then removed) but it brings some interesting benefits and makes it easier to manage certain cases ; I actually did my PhD on the late one. I remember how happy I was with the results (I even wrote a scientific paper on this. You can check it here.)

If you want to find out more details on what to expect from these protocols, I encourage you to watch this video below, in which I review them all in more details.

So we have protocols that can work… however, we only need to use in certain very specific conditions.

Estrus Induction : When can it be considered ?

Rule of thumb : we only consider this option when we are sure that there is no hormonal disbalance. 

That is why those first steps I mentioned above are critical.

We should always perform those few preliminary tests (hormonal assays, ovarian ultrasounds) to ensure there is no contra-indications.

If there is an ovarian cyst, playing with the hormones might do no good : it is a contra-indication 

Same if there is a sub clinical uterine condition.

If there is an underlying medical condition, we would attend this one first before attempting anything else. 

We also usually keep this option for very specific situations :

– Bitches that have never been seen in season (what we call primary anestrus) ;

– Bitches in which there is more than a 2 month delay in their normal inter-estrus interval (=interval between seasons) ;

We cannot use these protocols to “shorten” the inter-estrus interval (there are some hormonal limitations that make it not work if this one is not at least 4-5 months).

Anytime we can, we would prefer the bitch to have a natural season because this is when the best fertility results can be obtained. 

Estrus induction is only an option in those tricky cases.  

In our Yorker bitch, we ended up trying a medical protocol. 

It worked like wonder in her case : she got pregnant and deliver naturally 4 beautiful puppies a couple of months after. 

So as you can read, we have here medical protocols that are of great interest in canine reproduction. 

They can lead to fertile heats. They can help obtain puppies. 

As it happened in the case I described here. 

In a tricky one like this, it was an interesting option to consider and discuss.  

We can do pretty amazing things today. 

We have powerful tools.

They can help us achieve great results. When properly used.


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