[BLOG] Spaying & Neutering : the Rule of Diestrus


This blog was first published in Apr 2017 ; I re-edited it on Jan 2020.

This Friday, I’m doing a presentation on « Spaying and Neutering in Canines & Felines ».

And while polishing my Powerpoint, I couldn’t help but smile.

« Younger me » used to think that everything had been said and done on this topic.

Funny enough, in 2020, it is still a hot discussion in veterinary medicine.

And this is one of the lecture I am asked for the most actually ! (Must admit that is something I never anticipated 🙂 ).

Here is something I definitely love about biology: nothing is written in stone, we never stop reinventing everything.

The rule of diestrus

Fortunately for « younger me », few things on this topic haven’t changed.

For instance : spaying bitches during diestrus.

This is something I used to constantly repeat to our veterinary students back in the days in Paris,

And in 2020, this is still not recommended.

Diestrus = this 2-month period that follows the season, during which the corpora lutea on the bitch’s ovaries secrete the hormone progesterone.

Spaying during this period means an abrupt removal of this progesterone impregnation… which, in 20% of the cases – far from being negligible- , will lead to lactation.

Beware of persistent lactation

The  problem ? Because the ovaries have been removed, this induced lactation often persist… longer than expected..

I remember a small Yorkie bitch that had been spayed during this period…

She was presented to us because the owner saw her mammary glands were slightly enlarged… and blue !!! (That is actually what caught her attention).

When doing the clinical exam, we found out she was “lactating”.

( It was not what you would consider to be “milk” – the secretion was yellowish and rather clear – but there was definitely something produced by the mammary glands ; so that’s why in canine reproduction we would often say she was lactating).

And she did for MONTHS… before we were finally able to stop it thanks to a medical treatment !

Important for you to know : this type of lactation is described as a predisposing factor for the development of mammary tumors.

For sure, sometimes we don’t really have the choice.

In case of an emergency, we might have to spay during diestrus.

Routine procedure ? Be patient if needed

We know we have efficient medical treatments we can use to stop lactation.

But still, in this specific situations, it might take longer than expected to obtain medical success…

That’s why “no spaying during diestrus” is a rule I’ll definitely abide by when it comes to a routine procedure.

« When was her last season ? » is always an answer to ask during a pre-spaying consultation.

If the answer is « less than 2 months ago », I would definitely recommend then to be a bit patient.

I can indeed make a whole positive difference for sure.


2 thoughts on “[BLOG] Spaying & Neutering : the Rule of Diestrus

  1. Thank you Dr. Fontaine for your article. I just moved back into the small animal realm, so this article is right on time for me.

    Good luck with your presentation, although you won’t need luck. Do great!

    Dr. Turnera Croom


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