Cows and dogs? Surprised PETA is not all over that.
Can see why they would use cows, we eat that animal so probably a lot of cows to use however ever heard of “mad cow disease”? yea..would not want them using that.
Same for dogs...rabies.
The source of cow fetuses is from pregnant cows that are slaughtered for food use, and possibly from cows slaughtered for rendering. It is standard practice to test for the presence of prions, as well as several other pathogens. Fetal calf serum used for cell growth comes with certificates and there are rigorous standards for its production. This is a link to an organization that works to ensure serum quality. Also, FYI, several committees have met to discuss issues related to the ethics of collecting fetal calf serum--yes, they do recognize that fetal calves can experience pain. The horribly irony here is that there is often concern over humane euthanization of fetal animals, which never seems to carry over to the discussion of murder of fetal humans.
Same for dogs...rabies.
The dog cells, MDCK, have been used for decades. They do not contain the rabies virus.