Republican Senate candidate in Pennsylvania Dr. Mehmet Oz is under fire after a report revealed he was involved in scientific experiments that killed hundreds of dogs. His Democratic opponent, Lieutenant Governor John Fetterman, has called Oz a “puppy killer” on social media. Between 1989 and 2010, Oz and his teams of researchers at Columbia University conducted experiments with 1,027 live animals. Over 300 dogs died during this period, a review of 75 academic papers by Jezebel showed last week. Oz was a “principal investigator” at the Columbia University Institute of Comparative Medicine labs…