...or you could zeuter the dog, instead

The dog was on his back, sedated on a table. I was not wearing a surgical cap or a sterile gown. I held the first testicle between two fingers, pushed the needle in, and injected a little less than a milliliter of a mixture of zinc gluconate and L-arginine. Then the second testicle. And now the dog was non-surgically castrated. In a few weeks, once he was rid of the sperm he had already made, he would be sterile for the rest of his life.

This product, Zeuterin, is newly released in the US market, just starting to make its way into veterinary clinics. I was part of a one-day training at a low cost spay/neuter clinic which has partnered with the company as an early adopter. On the one hand: if we can avoid doing surgery on dogs, why wouldn't we? Isn't an injection better than cutting? On the other hand: if you have to sedate the dog for the procedure anyways, and surgical castration is so very quick and simple, what's the benefit of zeutering rather than surgically neutering them? And is the benefit to the dog (healthier) or to the human (faster and/or cheaper)?

I'm considering a few different populations of dogs: owned dogs being brought to a clinic, shelter dogs being altered on site, and owned dogs being altered on an outpatient basis. The answers to the above questions will differ for each population.

• Sedation versus anesthesia: Surgical castration of a dog requires full anesthesia. Zeutering requires only sedation, and in some calm dogs can be done without even that. A dog will recover more quickly from sedation than from anesthesia, so he'll be able to go home earlier in the day. (Important in a clinic and for outpatients; not important for most shelters.)
  
• Time: You'd think that an injection would be faster than surgery, but it isn't clear that this is so. A trained high volume surgeon will perform a castration (a very simple surgery) in just a minute or two. The injection has to be given slowly and the needle has to be positioned precisely. The time difference may not be significant.
  
• Cost: Zeuterin is expensive! It costs $10-25 to neuter a dog with this product, depending on the size of the dog. I don't think anyone really knows how this compares to surgical castration, which doesn't have clear costs per animal. How much is your surgical suite costing you, and how valuable is it to keep a dog out of it? How much does it cost to sterilize a pack of surgical instruments? For shelters where every penny is counted, the cost of the product will matter more than in a veterinary clinic where an owner may not mind a difference of $10 one way or the other.
  
• Using technicians: Technicians can't perform surgery. That requires a veterinarian. But a technician can give an injection. The spay/neuter clinic where I learned to zeuter are currently only allowing vets to zeuter, but they expect to start using technicians in this role as they become more comfortable with the procedure. Saving the veterinarian's time is a big bonus. Vets are expensive!
  
• Testosterone reduction: Surgically neutering a male dog reduces his testosterone level by 100%. Zeutering him reduces it by 50%. Which is better? Hard to say! We don't really know yet whether zeutering will reduce unwanted behaviors (roaming, peeing on things) the way neutering sometimes does. (But we tell people that really training is better for that sort of thing anyway.) And is it healthier for a dog to have all of its testosterone, or only half? Testosterone is a steroid which affects metabolism and various physiologic process in many ways. I'm guessing that it does some good things for dogs and some bad things, and only time and a lot of research will tell whether it's better to have 50% or 0% of normal levels.
  
• Aesthetics: Zeutered dogs still have their testicles, although atrophied and therefore somewhat smaller in size. Good or bad? Opinions will differ on that one.
  
• Complications: Surgical complications can include anesthetic death and bleeding, but complication rates for this simple surgery in healthy dogs are very low. Complications with zeutering include the development of ulcerations or even necrosis of the scrotum. These complications are also expected to be low when the procedure is done correctly, but again, it's too soon to know exactly how that will shake out.

So is there a place for zeutering in veterinary medicine? I think there is, but it's not clear yet exactly what it will be. I'm not convinced that that place is in a shelter (though some shelter vets disagree with me). I'm also not convinced it's in a general practice veterinary clinic for the average owner, although I think some owners will prefer Zeuterin both for avoiding general anesthesia and for maintaining a higher testosterone level, and of course for keeping the dog's balls. The place I really see this product is for performing neutering outside of the veterinary clinic, for example, in low income areas of the US where the population has difficulty getting their animals to a veterinary clinic, either for lack of transportation or for lack of enough committment to follow through with an appointment for surgery. In other countries, trap-neuter-release programs may also find a great benefit to being able to do this procedure in the field.

(Posted by a bleary DZ at the fabulous but overwhelming ScienceOnline 2013 unconference.)