When you hear the word “portholes,” you likely imagine small windows on a ship or airplane, but they’re also used in a very different context—on cows. Yes, you read that right. Farmers and scientists have been using portholes on cows to access their stomachs for decades. This controversial practice, while largely unknown to the general public, plays a key role in livestock research and agriculture. Here’s everything you need to know about the use of portholes on cows, their purpose, and why this practice is both praised and criticized.

What Is a Cow Porthole?