Vasectomized ferrets need to be some stage of 'rut' (male equivalent of bing in 'heat') to achieve 'bringing a jill out'. A castrated ferret is not a vasectomized ferret - it is a neutered ferret - just a clarification... A male is not always 'really' fertile while he's in rut - there is a higher sperm count at some stages than others but with a vasectomized hob breeding that is not a consideration. We're lucky in that we a a vasectomized hob who is extremely 'efficient and effective' nearly year round. He's a winer and diner instead of the more typical 'caveman' style breeder. About neuter/spay age. Maybe its arrogance but I'd rather not be lumped in a summary. Jills have been known to go into heat as young as five months but that is because the sunlight induced breeding cycles of ferrets has been disrupted since they've mostly moved indoors in the last decade or so. Breeding has been mostly an outdoor event since ferrets became domesticated up until the recent surge in popularity as real companion animals. We still recommend neutering no younger than 6 or 7 months. Neutering a male can be delayed as long as wanted - assuming no need to be 'friendly' to other males or toleration of urine perfume by the owner. Spaying a female is best if done before the first heat cycle but that is not imperative. It is trickier to spay (according to Dr. Kawasaki) when in heat but I do not know the specifics and know it is not as advisable. A coomon practice for breeders is to retire females after age three or four - and for males as well. Once retired it is much less strain on the animals to be spayed/neutered. The estrus cycle is hard on a jill and the solitary confinement of a hob in rut has got to be annoying for animals that have become so social as ferrets. There has been a lot of speculation on a connection between early spay/neuter and cancer but I've become very sceptical. A friend of mine had a ferret die of cancer after it retired from a breeding program - obviously not an early neuter. There is much creedence toa genetic connection in cancer which would be much more likely to be the cause of cancer in Marshall farm ferrets. They introduced new stock into their colony before the ECE hit and I hope this can help reduce the percentages of ferrets getting cancers. I wish certain overly political folks around here would be more aware of their facts before spouting off. bill and diane killian zen and the art of ferrets [Posted in FML issue 1232]