ETA: Working link to above article
Something to point out, that rebuttal article recites something *way* out of context. The study they are referring to with the %'s for mammary cancer risks were relative
risks - as in, corrected from the rebuttal paper:
In fact, the literature states that the risk of developing mammary tumors in dogs spayed prior to the first estrus is 0.5%, 8% after the first estrus, and after the second estrus the risk will increase to 26% relative to the risk of an intact bitch.
Which is, according to the JAVMA
, 3.4%. I really don't think more than 1 out of every 4 intact females wind up with mammary tumors (26%). So by spaying after the second estrus cycle your risk drops to 26% of 3.4%. You don't wind up with a 26% risk factor by waiting until after heat #2.
I didn't spot any other glaring flaws but when she misses something as large as this in a rebuttal article I am just as skeptical of her other claims as I am of Dr. Zink's paper (which to the author's credit does have numerous mistakes I can spot right off the bat, but as I'm unable to verify the studies either party is talking about, I'm not really willing to make any kind of decision based on either paper.)
The specific, and simple mistake I pointed out though immediately makes me pretty wary and suspicious that something more is going on than just a simple rebuttal. Her paper is peppered with the same kind of slants and misrepresentations as she is slamming Dr. Zinks for - such as not citing numbers for all the "life threatening problems" she claims threaten intact male dogs, things that "make (the case for) castration in preventative health care for male dogs" obvious.
Certain parts read less like a calm, collected rebuttal to a poorly written paper and more like a persuasive essay.
With that in mind I would hope nobody uses either of these articles to make this big of a decision. The rebuttal is just as bad as the original paper - which, as Dr. Howe pointed out, completely failed to mention a very significant concern for intact females, pyometra.
Good luck with your decision, OP. As long as you're deciding what is best for you AND your dog, and doing your homework on the matter, whatever decision you make will be the right one.