I read about this study in the past, seemed inhumane. Sometimes animal rights groups, like the ones claiming artificial insemination of cows is tantamount to rape, go too far, but in this case, from the article itself, there were worrying signs the animals did indeed suffer.

"One primate developed a bloody skin infection and had to be euthanized. Another was discovered missing fingers and toes, “possibly from self-mutilation or some other unspecified trauma,” and had to be put down. A third began uncontrollably vomiting shortly after surgery, and days later “appeared to collapse from exhaustion/fatigue.” An autopsy revealed the animal suffered from a brain hemorrhage."