Why not? We tattoo all sorts of food animals, which is what they were originally bred for (and I can confirm from experience that they are yummy — they are street food in the Andes).
Not that I have eaten the ones bred for medical research. But a fun side point: we did drug program for which the FDA insisted that preclinical studies be done in mini pigs (similar to human skin) though our research program had been in guinea pigs. The Göttingen mini pigs, like many experimental program animals, are carefully inbred so you can get a group that are genetically quite similar. We had to do the study in Toronto because the labs in California claimed they were being outbid by certain restaurants who wanted pork short ribs.
I was (and remain) convinced that this was some kind of racist joke (among other things these kinds of animals are quite expensive), but multiple people swore it was true.
So maybe you have eaten an animal intended for scientific research.
How things have changed. 30 years ago we said "please get your pets tattooed" because ear tattoos were how veterinarians reunited lost animals with their humans. Now we use RFID tags and tattooing is frowned upon.
