There isn’t any pain. You’re projecting your somatic delusion.
As I have already said, we are not talking about a human being in which the placebo effect can be strong enough to drown out the sensation of pain upon needle insertion. We are talking about an animal that has absolutely no comprehension of what is being done to it. That means that it will NOT have the placebo effect to mask the pain. Between restraining the animal and shoving needles into its flesh, its "caregivers" are subjecting it to needless pain and stress. I am surprised (and disappointed) that a veterinarian, who had to go through years of science-based training, would agree to subject an animal to this. Most veterinarians I know are highly compassionate towards animals.