More than 200 Iowa State University students joined Governor Branstad Tuesday to counter what they call a “smear campaign” against producers of finely textured beef. Branstad spoke to animal science students and others inside, as critics of the beef product gathered outside.

“It’s your future that is threatened if campaigns of distortion and smear are successful against safe, wholesome food products,” Branstad said. The finely textured beef has just recently drawn wide-spread criticism after being sold in stores and used in school lunches for two decades.

Critics oppose the use of ammonia to treat the product they call “pink slime.” Supporters, like Branstad, say beef trimmings in question have never made anyone sick.

“We need your help to combat this information and smears and replace it with accurate, scientific information that consumers can rely on,” Branstad told the I.S.U. students. Outside the lecture hall, the animal science students grilled hamburgers containing the beef product.

Around 40 protesters gathered nearby. A handful of independent farmers came from around the state to discuss the damage finely textured beef has done to small farms over the past 20 years. They claim the beef product has eliminated the need for more than a million cows mostly from independent farms since the 1990s.