This is frustrating that it's marketed as FDA approved but people won't recognize that it is regulated as a medical device, which have to only show safety, rather than as a drug, which have to show safety *and* efficacy.
OMG, I went down the rabbit hole on this paper and it is bonkers. Their methodology is amateur hour. It's just an uncontrolled non-validated survey sent out by an activist group. What is their list of survey recipients based on? What were the demographic differences between responders and nonresponders? It's the science equivalent of a political push-poll (https://en.wikipedia.org/wiki/Push_poll)
The first author is a business executive who launched a huge class-action against Merck without disclosing it in this paper, the only veterinarian in the authors has been cited for practicing without a license (https://www.ocregister.com/2021/10/26/founder-of-hemopet-in-...) and the senior author is an orthopedic surgeon with no relation to the field and has maybe one other publication.
They target gamma-aminobutyric acid chloride channels (GABACl) that aren't present in mammals. There is a relatively narrow therapeutic index in animals, but generally felt to be safe at approved doses. They're given to millions of animals, so we'd probably know if there was a problem.
"I have not witnessed one machinist harmed by lead in 40 years." Do you know what you're looking for? Lead poising can be subtle but eventually devastating. This is like the asbestos industry saying that miners didn't get harmed because they didn't follow up with them years later when mesothelioma slowly strangled them.