aggression after speying in ferrets

Question
I have a client with 5 female ferrets and one male. We don't deal with ferrets very much as it is illegal to keep unspeyed ferrets as pets in New Zealand.
We recently speyed the 4 younger females, who I believe are offspring from the older female. She was in season at the time so we gave her a gonadotrophin injection to take her out of season. We then speyed her 2 weeks later.
The client recently was in and told us the older female now is very aggressive towards the younger female ferrets and as we dont deal with ferrets often we aren't that knowledgeable about their behaviour.

Thank you

Amy

Answer
This is a tough one.  I would usually attribute aggression, especially sudden aggression, to adrenal disease.  In your case it is unlikely due to the recent spay, although not impossible.  Other causes of sudden aggression are usually medical in nature and not behavioral.  You may want to try to contact a ferret vet.  It sounds like there have not been any changes other than the spay to account for a behavior change.