Since I know we have a lot of discussions about managing canine reproduction responsibly here on Chaz, I figured I'd share my research on spay options here, as well as on fb. Both people I consulted for this are reproductive vets - the information is from our phone consults. Information from Dr. Diaw in NC State's Therio department: Traditional spays and ovariectomies are pretty much the exact same in terms of effect on hormone levels and risks because you are removing the ovaries in both and that's the source of hormones. It's personal preference on which procedure you use - Dr. Diaw practiced in Europe and is now at NC State and he says he saw no differences between the animals he spayed with OVE in France and OVH here in the US. When it comes to pros and cons, OSS is pretty much equal to keeping a dog intact, but without a uterus to create discharge. With hormones present, you'll see less incontinence (when compared to spayed females), full bone development in younger animals, possibly lower rates of some cancers (though this is very breed dependent according to Dr. Diaw). You will see higher rates of mammary tumors and ovarian cancer. A note on the mammary tumor front: if you spay a female after her 3rd or 4th heat, the risk of mammary tumor development is the SAME as if she'd been kept intact. Spaying before first heat = 2% risk, spaying after 1st heat = 4% risk, spaying after second heat = 8% risk. Ovarian cancer is generally rare in dogs. Dr. Diaw did say that he has noticed a correlation between females who lactate during false pregnancies and those that develop ovarian cancer later in life, but he was quick to say that this is anecdotal. Without the uterus, dogs still cycle, but because the entire uterus down to the cervix is removed, there is no risk of stump pyometra and there is no discharge. Females will still swell and can be attractive to males. A male can also breed a OSS'd female, which can be VERY dangerous. Dr. Diaw did relate a story of an OSS'd female being bred by a much larger dog, which resulted in hemorrhage and ultimately death because the end of the vagina/cervix was perforated. He did emphasize that he'd only heard of this one case, but that it is something they warn people about when OSS is discussed since it means OSS'd dogs still need supervision during points in their cycle. The complete removal of the uterus is key in this procedure - most vets do not remove all of the uterus in a traditional spay so it *does* require a vet knowledgeable in the procedure to do it correctly. This contributes to the difficulty in finding a vet who can perform the surgery and this scarcity means higher prices. Information from Dr. Barber at Veterinary Specialties at the Lake: Dr. Barber confirmed that there is no hormonal difference between traditional spays and ovariectomy. She tends to prefer ovariectomy because it requires a smaller incision and thus is faster when it comes to recovery time. She's not seen *any* pyo in a female without ovaries in her practice.When it comes to OSS, Dr. Barber has done several herself, but they aren't in demand enough to draw major conclusions, even anecdotal, past what we know about the effect of hormones on various body processes. Research is still severely lacking in this area and it's difficult to find a vet experienced in the procedure. She did confirm that OSS'd females will be attractive to males at roughly the same level as an intact female due to pheromone production, that swelling will be similar to that of an intact and in heat female, and that with the removal of the uterus you will have little to no discharge. She leaves both ovaries, but when I asked about leaving just one, she said that it might reduce hormone production slightly, but wouldn't change the female's cycle at all. The only benefit she could see to leaving just one ovary would be halving the risk of ovarian cancer, but in dogs that isn't nearly the concern that it is in people. I did ask about the danger of injury with a tie that Dr. Diaw mentioned and she said that she hadn't heard of anything like he described but that it would be a similar risk for a size mismatched pairing in an intact female as well. The issue would be the length of the vagina, which does NOT change after OSS. Recovery with OSS is similar to a spay - the incisions are very similar in size. The surgery generally takes a bit longer since you have to be more careful about removing all of the uterus. Dr. Barber *did* give me another alternative for those who want to control heats but are on the fence about permanent sterilization: Mibolerone, aka Cheque Drops, an androgen. The product is no longer available as Cheque Drops due to lack of demand, but can be compounded with a vet's prescription. Mibolerone will prevent intact females from cycling, though it's not 100% in all breeds, especially "Alsatian types". The cost is not insignificant ($75-100/mo/dog for my 30-40lb dogs), but it would allow owners to trial without the worry of heats and lost entries. Dr. Barber also said that it can be a handy way to see how a dog might behave after traditional or ovariectomy spay without the permanent effects of surgery if there are concerns about the removal of female hormones in relation to aggression. Dr. Barber feels that mibolerone is quite safe, and she uses it with a number of her patients currently. It is recommended that it only be used for up to two years if one wants to preserve reproductive capacities after use, and no info appears to be available on effects of use longer than that. A couple of disadvantages were mentioned: when dogs are removed from mibolerone, the next heat can be VERY unpredictable, coming 3-270 days after the medication is stopped, mibolerone should be started *at least* a month ahead of an anticipated heat to be most effective at stopping it, and it does not appear to assist in syncing heat cycles in dogs. Lots of info to muddle through for me, but hopefully this is also helpful for others! For those interested in furthering research into reproductive health in animals, check out the Theriogenology Foundation (http://therio.org/displaycommon.cfm?an=1&subarticlenbr=332) - this is an organization devoted soley to research into various reproduction topics in animals. They provide grants and accept targeted donations from individuals as well. Dr. Barber highly recommends them!