In recent times we have allegedly witnessed a “post-truth” turn in society. Nonetheless, surveys show that science holds a relatively strong position among lay publics, and case studies suggest that science is part of their online discussions about environmental issues on social media — an important, yet strikingly under-researched, debate forum. Guided by social representation theory, this study aims to contribute knowledge about the role of science in everyday representations of livestock production on social media. The analysis identifies two central themata, namely lay publics' contestations of (1) facts and non-facts, and (2) factual and non-factual sources.