Ovariohysterectomy versus ovariectomy, is removal of the uterus necessary?

Ah, United States’ medicine vs. European medicine, the war rages on. The battleground I’ll discuss today: elective sterilization of the female reproductive tract.

Image from Penn State Virtual Cat Dissection

This discussion came up in JAVMA recently, and I felt it warranted a look from a future vet. Granted I don’t have all the information and education here, but given that I’ve only ever seen ovariohysterectomy performed in practice, I’m interested in why we actually choose to remove the uterus as well.

Much of the article discusses the benefits gained from the simplicity of the ovariectomy procedure. With the potential to use laproscopic techniques, smaller incisions, and less manhandling of the abdominal cavity, post surgical pain and complications can be markedly reduced in both cat and dog patients. More specifically, better exposure of the ovarian pedicle due to the incision location allows for complete excision of the ovary, suggesting that the surgeon will be less likely to leave any remaining endocrine tissue.

Outside of the surgery itself, the authors discussed the often cited benefits of spaying companion animals, and how the two techniques alter the statistics. Unfortunately, there were little to no studies directly examining the incidence of these benefits when comparing groups with or without a uterus, and some of the numbers they did find were inconclusive or conflicting. I found it interesting to see some of the actual odds concerning the prevented conditions we advertize when discussing spays, the most common being mammary and uterine tumors.

The potential for mammary tumors seems to be the most significant of the spay benefits. Their overall incidence is 3.4%, with 41-53% being malignant (DeTora, 2011). If spayed before first estrus, that risk drops to 0.5%, which is huge! Almost all of the benefits from spaying come from the removal of sex hormone cycling, which seems to be largely necessary for many of these tumors to form (not surprising, as I had previously discussed how estrogen appears to have an immune boosting effect, which would promote chronic inflammation that we know to be an important risk factor for many cancers). The authors point out that as hormone cycling is prevented solely by removal of the ovaries, that all of the future medical benefits of sterilization are gained without removal of the uterus.

The only medical benefit correlated with sterilization that is obviously tied to removal of the uterus seems to be uterine neoplasia.  However, most uterine tumors are benign, with only 0.003% being malignant as well as easily treated with hysterectomy (DeTora, 2011). The authors also found no case of uterine neoplasia ever reported in a dog that had had its ovaries removed before 2 years of age, making this benefit of ovariohysterectomy moot.

While I do think that the authors wrote this commentary with an obvious preference for ovariectomy, the assumptions they made seem rational; and even though there wasn’t enough data to declare one technique superior to the other, I agree with the conclusion that the United States’ preference for ovariohysterectomy cannot be supported by the currently available evidence. However, there is no obvious disadvantage to the procedure, and whichever technique that specific surgeon is most proficient with will probably be the best choice in any situation.


ResearchBlogging.orgDeTora M, & McCarthy RJ (2011). Ovariohysterectomy versus ovariectomy for elective sterilization of female dogs and cats: is removal of the uterus necessary? Journal of the American Veterinary Medical Association, 239 (11), 1409-12 PMID: 22087712

Article review: Effects of early pregnancy diagnosis by palpation per rectum on pregnancy loss in dairy cattle

Image from UPenn

Just a short one here today. Not too much interesting going on in a study that supports the null, but the methods are great.
This study looked at the affect that one or two rectal palpations to determine pregnancy had on embryo viability. I can see why there would be a question, it seems like a highly invasive procedure when you’re shoulder deep in cow rectum and feeling for an amnion several layers of membranes away. But we tend to anthropomorphize, and many dairy cattle require minimal restraint for the procedure. Nonetheless, it does seem likely that there could be a negative effect on the embryo, especially when rupturing or crushing the amnion via rectal palpation has been a historical method of terminating an unwanted pregnancy in cows (before we started using PGF2α) (Romano, 2011).
The study did a great job of identifying factors that have created conflicting results in the past. Whether that was sampling bias, uncontrolled treatments (multiple people and techniques for palpation), or a lack of a true control. They took the time to show how each one of those shortcomings was corrected in this study, and I think they did a great job designing the experiment.
In the end it was surprising to see that there was no difference between the cows subjected to rectal palpation once or twice compared to the control. I didn’t expect to see a significant difference, but potentially a small one. The authors did warn that because this experiment was so controlled, the results may not be similar to every situation. Inexperienced personnel or different techniques could change the pregnancy rates in practice (the study employed a single veterinarian with >25 years experience). One difference they took time to note was the much lower pregnancy rate in dairy cows as opposed to primiparous heifers. The exact etiology of this is unknown, but is commonly found in dairy. The authors mention it as it played a role in their analysis of the two farms involved (other factors affecting rates between the farms were geographic area, rate of twinning, and breed of cattle).

Not especially exciting, but it’s always great seeing researchers identify a conflicted area and tackle it with strict methods/controls and a large sample size.

ResearchBlogging.orgRomano JE, Thompson JA, Kraemer DC, Westhusin ME, Tomaszweski MA, & Forrest DW (2011). Effects of early pregnancy diagnosis by palpation per rectum on pregnancy loss in dairy cattle. Journal of the American Veterinary Medical Association, 239 (5), 668-73 PMID: 21879969

Article Review: Epidemiology of Surgical Castration in the United States

I recently had a professor tell me that if I didn’t let them know if I made it into vet school, they would forever curse me with fat, in heat, Labrador spays for the rest of my career. I can think of few fates worse for a future veterinarian (though I did mention that the owners also had to have  no way to pay, and will forget to mention this until after the procedure). Today’s article is really cool and discusses the prevalence of ovariohysterectomy and orchiectomy (spaying and neutering, fixing, castration, gonad removal,de-nutting, whatever you prefer to call it) in the USA. It breaks the percentages down into region, animal species, animal breed, animal age, and enrollment in wellness plan from Banfield (animal health insurance).

Banfield Pet Hospital is an amazing organization for animal research because all of their records are computerized and kept in a central database (I should mention that the man who made Banfield what it is today is an OSU alum, go beavs). Because of this treasure trove of data, this study was able to get a sample size of over 300,000 cats and over one million dogs. While this represents less than 1% of the US pet population, its still a valuable amount of data, and we can reasonably assume that Banfield has a decent representation of the rest of the pet population that regularly visits private clinics. The article mentions that one of the only large differences is the mean age at clinics (Banfield’s is slightly lower). The numbers found in this study also line up well with previous examinations using distributed surveys to collect data.

I’m very proud to say that the Northwest region (making up Washington, Oregon, Idaho, and Montana) has the highest percentage of castrated cats and dogs compared to any other region (tied with the North Central region for percentage of dogs) according to the study. The region with the lowest percentage was the Southeast region (making up Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, and Tennessee). That’s an area of the country I haven’t ever visited, so I can’t comment on cultural factors that may influence the decision to castrate pets, but clearly more outreach could be focused on that area.

The breed distribution is interesting, but doesn’t offer too much information for most breeds. In my own head I see the Labs’ and Retrievers’ high numbers understandable, as you can in some ways consider them “white-collar” or suburban dogs. This would be associated with a higher income and thus one less roadblock to castration. Pit Bulls can maybe be considered a “blue-collar” dog, but that can’t be the only reason their numbers are so low. I’m actually at a loss as to why the castration rate of Pit Bulls is so much drastically lower than all the others. It’s an obvious outlier. I myself love Pits and believe that in the right hands they make great dogs. But considering their stigma, low rate of adoption (and consequently high euthanasia rate), insurance liability, and higher risk, I do believe we should make castrating Pits a priority. I’ll definitely be looking for more literature that attempts to explain the demographics and other factors that create this problem. The second lowest group, Chihuahuas, is also interesting. Again, I’m not sure why the numbers for this breed are so low, but one factor may be that many Chihuahua’s are kept as indoor-only dogs, and that may reduce the motivation to perform the procedure, as the largest benefit is wasted on them (as seen by those owners).

I’m not surprised to see that mixed animals were more likely to be castrated, and I really have no problem with that. There aren’t too many unwanted animals that come from intentional breeding, and purebred animals generally don’t have trouble finding homes (pending behavioral issues). Responsible breeding doesn’t contribute to the pet overpopulation problem significantly, and leaving that option open to purebred owners is acceptable. With cats on the other hand, I’m happy to see the extremely high rate of castration. Cats are allowed to roam unsupervised much more than dogs, and we have enough trouble controlling the feral population without accidental pregnancies also occurring in animals that could have been easily castrated.

One rather frightening statistic was the percentage of dogs and cats from shelters that do not return for castration. This concerns me as in many cases the cost is free or subsidized to less than $50. In a private clinic you can pay upwards of $200, but this seems to be little incentive as 40-60% of animals are returned for the procedure when it is already paid for. To me, this is indicative that some of those owners will provide a low level of veterinary care for the lifetime of that animal, when they already haven’t taken advantage of a free procedure. This is pure conjecture however, and there could be a host of reasons that owners do not return. However, because the rate is so low, I would bet that there is some significant factor that is relatively consistent among owners who adopt from shelters, whether that be income (shelter’s are a very inexpensive option to get a purebred-looking dog) or attitude.

All in all, a good look at where castration is common, and where education and improvement needs to be made.  I do think that many PSA’s, advertizements, and advocacy campaigns are too often directed at groups that are already in agreement. Even looking the statistics from a PSA I made back in high school show that the primary people concerned with animal welfare are women over 35, and it’s clear that similar announcements are marketed at that group. New campaigns should focus on a new approach to educate people why castration is important, and maybe spend less time showing us pictures of sad puppies. Tell me why I personally should do it, because until it’s too late to change anything, there’s no reason I should think I’m part of the problem.

ResearchBlogging.orgTrevejo R, Yang M, & Lund EM (2011). Epidemiology of surgical castration of dogs and cats in the United States. Journal of the American Veterinary Medical Association, 238 (7), 898-904 PMID: 21453178

Article Review: A review of the causes of poor fertility in high milk producing dairy cows

The more I read, the more I’m extremely grateful for the rigor that my reproduction class required. None of this would have made sense to me last year, and it’s amazing how many of the details I’ve been able to keep in my conscious memory. I’m sad that I’m missing the advanced repro course offered in the fall, but hopefully the experience I’m gaining here will be just as valuable, and I can continue applying what I’ve learned so that I don’t lose the knowledge.

I was extremely impressed with this article. It felt like a lecture rather than a textbook, and as a reader it was easy to finish, but still full of great content. The focus is on how while our dairy cows have been engineered to crank out milk, we’ve seen a dramatic drop in their reproductive success which hurts the efficiency of dairy operations.

Pretty amazing what selective breeding can do. But we knew that, we managed to make dachsunds from wolves.

The article explains that rather than a minimalist approach that looks at only one factor (such as inadvertent selection for poor reproductive fitness) to correct the problem, a more inclusive or holistic approach is needed. I learned a lot more about common problems such as lameness, mastitis, metritis, and poor BCS and how they relate specifically to resumption of estrus after parturition and zygote viability. I’m always amazed how farmers can actually succeed at maintaining herd numbers when conception and birth rates are so low.

There was a lot written about heat stress, and that always seems obvious when it gets over any comfortable temperature. But heat and other environmental stressors are actually a lot more dangerous to reproductive health than I was aware. According to the article, “exposure of ovarian oocytes to unfavorable physiological events during follicle development from primadorial to pre-ovulatory stage may result in the ovulation of defective oocytes up to three months after the insult (Britt, 1992; Fair, 2010).” When you have 60-90 days to breed your cattle to stay on schedule, this is extremely influential to your breeding program. This also makes the situation down in Texas more dangerous in that, with the dry weather during their normal wet season, any excess stress surrounding parturition could delay or destroy what’s left of their breeding program. Once they can’t even breed replacement heifers, its all over.

So, after looking at multiple conditions that hurt reproductive efficiency and discussing their prevention. The article sums itself up with a nice poster identifying the key areas they covered.

(Walsh, 2011)

For the causes and preventative measures covering these you can check out the article. It finishes up by making the point that we can’t just develop a new antibiotic for metritis or mastitis, but we need to reevaluate our genetic selection and more importantly, our management strategies to ensure as many of these factors are met as possible.

Walsh SW, Williams EJ, & Evans AC (2011). A review of the causes of poor fertility in high milk producing dairy cows. Animal reproduction science, 123 (3-4), 127-38 PMID: 21255947

Research: Incorporation of Sexed Semen into the 7‐day CO‐Synch + CIDR Estrous Synchronization Protocol

Sexed semen has the potential to completely change the industry. If pregnancy rates with altered semen continue to improve, we could see not only major efficiency upgrades in cattle production, but the reduction of many practices animal rights groups would like to see end. A great example is the veal industry, which is perpetuated not so much from a consumer demand for veal, but for a need to recuperate costs from unneeded male calves in the dairy industry. Being able to avoid the negative public image of producing veal calves by using sexed semen would be an appealing option for many milk producers. This proposal is exploring the financial benefit of using sexed semen in beef cattle production (in which weaned steers sell for 15% more than heifers).

The study will be simple, but with an awesome sample size of 450 cattle. We will synchronize estrus using a controlled intravaginal drug-releasing device (CIDR), along with other synchronization methods I need to do some more research to explain. For an overview of several CIDR methods you can look here. Serum concentrations of progesterone will be used to determine if normal estrous cycles are occurring, after which we will use standard AI techniques to inseminate the cows with either the sexed semen or the control semen.

When all is said and done, we will not only examine pregnancy rates, but the performance of the offspring in growth and carcass quality. The overall picture will provide the best financial perspective when examining the feasibility of using this technology in the future.

It’s a cool study, and I’m excited to see if the pregnancy rates with the sexed semen are high enough to start incorporating it into mainstream production. The large sample size is great because that makes the conclusions from this study have weight for producers that take financial risk in the future trying to incorporate sexed semen into their programs. Few studies examining sexed semen have had large enough sample sizes to validate their results. Additionally, this study is the first of its kind to examine a direct cost-benefit relationship of using the new technology in comparison to the established methods.

You can read the full proposal here.

The Craigslist Hermaphrodite Chicken

That caught your attention, didn’t it? I’ve been watching Craigslist every day because I want to add two more chickens to my flock and if anyone puts them on there for free you’ve got to nab them quick. I haven’t had much luck since spring ended on nabbing free layers (roosters are a dime a dozen), but I came across this posting that made my jaw drop. Here’s the text for when the post is taken down.

Ameraucana chicken (albany)

Date: 2011-06-20, 5:54PM PDT
Reply to: sale-4zguk-2452639946@craigslist.org [Errors when replying to ads?]


True hermaphrodite chicken
Bought at the state fair last year as the first place lavender ameraucana pullet

later laid a too large egg that damaged an ovary.. which became a testical…1 in 1000 chance
began to grow cox comb and spur buds.
still lays a nice greenish blue egg now and then but thinks she is a rooster which she now is also.(can fertilize other hens but not itself)
A chicken no one else you know will have! Beautiful coloring, again she won first in her class at state fair last summer.

Nice and my kids will miss very much but our primary rooster wins out. though they get along great and s/he’s a great conversation piece I can’t afford an extra chicken that doesn’t pull the weight it was meant for.

Bought for more but will sell for $20
email if interested
pic from when brought home from fair last sept. also the only chicken not afraid of dogs. will just peck at their noses till they back off

  • Location: albany
  • it’s NOT ok to contact this poster with services or other commercial interests


Yeah. I figured this guy was off his rocker. But, as I don’t really know all that much about chickens, I shot an email to my reproduction professor from last term, Dr. Fred Menino.

“Hi Dr. Menino,

I came across this craigslist ad that seems…like questionable information. I can’t see how any hermaphrodidic chicken would actually be a result of a “damaged ovary” and spontaneously become a fertile testicle. Espicially considering the other ovary is essentially non existant and he claims it still lays eggs. Are any of the claims made here possible in any way? Or is this guy completely off his rocker? I’d appreciate the insight or hopefully give you a laugh.”

He got back to me very quickly, and kind of blew me away.

“HA!!! Hi Austin!!! Good to hear from you!!!

This is like something you would read in the National Enquirer….BUT, believe it or not, there is a physiologic basis for some of the things this poultry entrepreneur is talking about!!! There is a phenomenon known as the “ambisexual versatility of the bird”…..I attached a link. I used to talk about it in ANS 316 but the poultry classes pick this up (I think?!) so I dropped it from my class.


Anyway, birds are weird………if you do certain manipulations to a hen (genetically female), you can alter her phenotype: 1) if you remove the left ovary before 20 days of age, the right ovary will develop into a functional testis and produce androgens and sperm. The hen develops rooster-like qualities but there’s no male ductwork leading to the cloaca!!! 2) if you remove the left ovary between 20 days of age and sexual maturity (18-20 weeks of age), the right ovary will develop into an “ovatestis”, an organ which has both follicles and seminiferous  tubules!! 3) lastly, if you remove the left ovary after sexual maturity (18-20 weeks of age), the right ovary will develop into a functional ovary, however, it will lack the oviduct to connect to the cloaca.

The question with this guy’s chicken is:  if the damage to the left ovary occurred before sexual maturity and an ovatestis developed, could sperm and/or eggs, as he suggests, be shed into the rudimentary oviduct that would be present?? I guess anything’s possible….maybe I should buy it and do a necropsy to see what the heck is going on??!!!!

Take care,


I had half a mind to take him up on that offer and buy the bird just to study it and assist in that necropsy. I wonder how the poster would feel about that, maybe I would leave that part out. This bird is just weird, super cool, but weird. The very idea of a sexual genotype producing a viable opposite phenotype is remarkable, and kind of breaks a lot of rules biologically. Though I’m sure there are dozens of similar or stranger things like this in the animal kingdom, but outside of weird marine life, I’ve never heard of anything like this before.

Here’s a wild sci-fi thought though, what if we could someday manipulate this so that we could breed chickens that are self-fertilizing, and would only produce gametes with XX so that we could create a self-cloning layer breed. Then we wouldn’t have to destroy all the useless males produced in our industry layer breeds! There would be a dangerous loss of genetic diversity within the stock, and they would be extra susceptible to being wiped out by disease or anything tailored to them, but the idea is exciting. No doubt they’ve tried it somewhere along the line. The real marketing question though, is that while animal rights groups would be (hopefully) satiated with no longer having to destroy male layer chicks, would the public accept and purchase eggs from genetically manipulated hermaphroditic birds?

Article Review: Effects of acclimation to human interaction on performance, temperament, physiological responses, and pregnancy rates of Brahman-crossbred cows

Came across this article when searching for stress studies in cattle. I’ve been more and more interested in examining behavior and stress as I’ve read more Temple Grandin. I think it’s a field I can explore as I look for things I want to do with my DVM. Don’t get me wrong, I love working with clients and animals in a clinic setting, but I don’t see myself as a business owner, and I really want to look at what else is out there. Options I’ve been exploring are USDA jobs, lab work, and of course research through the college and elsewhere. Anyway, Giovanna Rosenlicht got me into the habit of reading journal articles in my spare time, which is great and actually really interesting….I am a nerd.

Anyway I don’t have too much to say about this article, the methods are sound and thorough, 395 animals used is a sample size I can get behind. Too many studies especially with companion animals have pitiful sample sizes of like 20 animals. Anyway, following reading the discussion, the dramatic difference I expected to see in the people acclimated group was not present. However there was a final statement that acclimation did have an inconsistent positive effect on reproduction success.

I have a vested interest in animal welfare, and I strongly support an approach that helps the industry see benefit, rather than dig trenches. Studies like this are the only way non-radical, educated, and effective welfare decisions can be made. What happens when people try to make knee-jerk responses to animal welfare? Look at the ban on horse slaughter and the subsequent problems associated with that piece of feel-good legislation.

Anyway, I get sidetracked, this post was supposed to be concerning the article. One of the main points that is crucial to the focus of the study was the correlation with excitable temperament (as often seen in Bos Indicus ancestry cattle) and elevated cortisol concentrations; which are detrimental to multiple physiological systems in the body, and result in “subclinical health disorders that negatively affect cattle reproduction, such as lethargy, lameness, and immunosuppression.” With cortisol levels (along with epinephrine and many other endocrine secretions that are a result of handling and housing stress) being a quantitative measure of animal health and contentment, this data will add onto the already large stack of evidence that the better we treat our meat/eggs/milk, the better product we receive.

It’s unfortunate that a larger and more consistent correlation was not found within the study, but the data is still sound, and definitely leaves room for further study in specific age groups, species and breeds, and other acclimation techniques.

It is also worth mentioning that this research was carried out in Florida, but one of the authors is now doing research at the Oregon State Burns research station. I’ll be looking for and have found many related articles from that location/author and will be discussing more of those in the future.

Newsworthy: Males Make Pregnant Horses Abort

I’m not a horse person, and I don’t think I ever will be. I think to truly be a horse person, for better or worse, you need to spend many years in their company. They’re not like dogs who have been so selected for companions that we understand their emotions even if we are not behaviorists. Additionally it’s harder for us to comprehend the way a prey animal views the world, much as it’s hard to understand the thoughts of people with severe phobias, OCD, or Autism (of course, if you’re Temple Grandin, this does not apply to you 🙂 ). In short, a relationship, whether as master, companion, or physician between yourself and equine needs to be developed before you can operate on a “horse person” level.

Until that day, I’m limited to looking at horses in an abstract sense, an academic one. My efforts to get to know these animals through playing Polo have been mildly successful, but I still don’t feel the understanding that I do among other animals, whether it be a feral cat or an old retriever. Heck, I feel like I understand cattle better than horses. However, I am still very interested in their physiology, behavior, and interactions. I’ve greatly enjoyed riding and spending time with these animals, maybe I’m on my way.

My news browsing today led me to this article. Which was really neat because I just finished the horse maternal behavior in my behavior book (Houpt) that I’ve been reading in my spare time. Obviously traveling to use a foreign stallion to breed your horse is extremely common, as you may be paying for some race winner etc.. Protecting that investment and avoiding a needless abortion of the foal you paid for is important.

The article is interesting to me however, because the implications of messing with natural animal processes here show a direct loss of revenue from an industry perspective. I am not a holistic or natural training/management supporter, nor do I agree with any of the principals and claims made by animal rights supporters, but animal welfare is a goal everyone should strive for, and improving animal welfare benefits both the producer as well as the animals they are utilizing. The article suggests that mares who have just been bred away from home should be allowed to freely mate with stallions at home, using vasectomized stallions so that you don’t inadvertently breed a foal that you do not want if the desired breeding was unsuccessful.

This could also provide the benefit of unwanted males still having an industry job, if their genes are not desirable, they don’t need to be culled or shipped to mexico to be processed for meat (if we could once again allow horses to be used as meat in the US that would be ideal…), they could be used as the “home males” that prevent abortions resulting from their presence  following breeding.

Midway through writing this I realized I was basing these assumptions based on a BBC news report, so I went ahead and found the original article (not sure if non ONID users can use that link).

After reading the actual article, my assumptions remain supported, that mares who were in the present of home geldings or stallions across a fence (unable to solicit coitus to confuse paternity) were 7 times more likely to abort than those allowed to have direct contact with familiar males. Though I was wrong that this should be implemented as an industry practice, as housing bred mares in their own enclosure with no other males present or nearby has even higher reproductive success.

That’s enough thoughts on this particular article, but I will say this, the possibility implied in the discussion that mares may be able to consciously choose to abort their foal though an unknown mechanism, is really cool.