Hi, I’ve always opted for the neutering option if I don’t plan on breeding from my ferrets. I did my research at the time and weighed out the pros and cons for a fair while. I would personally never opt for the implant in a female unless it was for control of adrenal or cushing’s etc, as in full females it’s been proven to shrink their reproductive organs and I’ve been told it affects their behaviour as well, though I’m not sure how true that part is. I again wouldn’t opt for the Jill jab as it isn’t really a long term solution and I don’t think that all of the artificial hormones are good for them. Some argue that removing those hormones are worse but that’s where factors like like adrenal come in. I’ve only ever had one of mine jabbed to bring her out of season for spay. All I know for certain is that a constant season is very bad for them, some choose to put their females in with a vasectomised male to bring them out of season, but then they can come into season very quickly again or in some situations the vasectomy can reverse itself and the Jill could become pregnant. All of my lot are neutered, and I got four of mine done a couple of weeks ago as they’re last years babies, and the vet was more than happy to perform the operations.
Personally I would always choose to neuter, there is a higher risk of adrenal disease but unfortunately ferrets can be prone to tumours which are completely unrelated to whether they’re neutered or not.
One reason some vets choose to push the implant is because it’s more expensive than neutering and it needs repeated every couple of years so it’s a good money-maker for them. Also the neutering itself is more intricate because ferrets are such small animals, however I think it’s unreasonable for them to outright refuse to neuter.