"Ever since I was little I loved animals," she told the org in an interview. "If you told me I could never sing again, I'd say that was horrible, but it's not my life. If you told me I could never be around animals again, I would just die."
The 29-year-old's love for animals comes from her childhood growing up on her parents' Oklahoma farm. Her switch to a vegetarian diet also happened there - with one moment in particular making her realize where the meat on her plate was coming from.
"My whole life, we always had cows. Everybody had cows. People had sheep. People had everything and I never thought why. I'd eat my hamburger, or we'd have spaghetti or bologna or hotdogs or whatever, and I just never thought about it. It never crossed my mind what that used to be," she told VH1's Behind the Music.
It wasn't until she saw her parents banding cows in the pasture that she confronted her mother about the cruelty.
"I was mortified. I said, 'Why do you do that?' And she said it will make them grow bigger. And ... light bulb! I was horrified and sad and I just couldn't believe this was happening in our pasture," Underwood recalled.
For those not in the know, "banding" is a common method of castration where farmers put a tight elastic band around the neck of the scrotum to cut off blood flow and kill the testicles. The testicles then fall off. Unfortunately, it's a practice that is often done without any form of anesthetic.
Check out Carrie talking about the experience for "Behind the Music" below.