Regulating Rumensin : defining antibiotic feeds in the U.S. in the wake of resistance

Abstract

This paper emphasizes the need to tell more histories about the specific cultural and chemical properties of antibiotic livestock feed to better understand its adoption and use in the past and today. The existing literature about U.S. antibiotics in food production provides important but generalized takes of agriculture’s “antibiotic era.” The history of on-the-farm antibiotics demonstrates how historical alliances between producers and scientists formed, how shifting definitions of abundance and purity impacted antibiotic adoption, and how science has been used to “manufacture uncertainty” about the impact of these technologies. Despite these contributions, few address the differences that exist between antibiotics, or how these differences affect their development, adoption, regulation, and use. To stress the particularities of antibiotics, this paper tells the story of Eli Lilly’s Rumensin from the lab to the trough. The history of Rumensin details why it is difficult to regulate some agricultural antibiotics in the United States. Since its inception in 1975, Rumensin has largely been seen by scientists, policy makers, and producers as the “successor” or “replacement” feed technology to prior problematic ones: namely sulfaquinoxaline, which became inefficient for treating coccidiosis, and diethylstilbestrol, which proved carcinogenic. Rumensin was also one of the first feed additives developed for exclusive use in agricultural animals. Rumensin’s chemical compound, called monensin, had not been used in human medicine prior to its adoption and use in livestock farming, like most other antibiotics had been. This strict definition as a medication for non-human animals continues to contribute to Rumensin’s exemption from a Food and Drug Administration defined Veterinary Feed Directive (VFD) drug status. Further, a focus on the use of Rumensin in cattle shows how decades-long debates about it has hinged on how scientists, farmers, policy makers, and the public understand what monensin does in cattle bodies. When Eli Lilly first marketed Rumensin in the U.S., they emphasized its role in the rumen as a feed-to-food converter rather than as an antibiotic coccidiostat. Their advertisements focused on the role of the rumen, which Lilly illustrated with a glowing white orb placed on the stomach on a steer. To cattle farmers in the late 1970s, Rumensin’s status as a “feed efficiency tool” seemed inferior to DES’s status as a growth promotant. However, over time, policy makers argued that Rumensin was the ideal DES successor as an alternative growth promotant. The way monensin worked at the cellular level led to an entirely different scientific classification of antimicrobial – the ionophore – which popularized as a term in agricultural communities that hoped to avoid publicly-charged hormone and antibiotic feeding. However, the term “ionophore” had little significance outside agricultural and regulatory infrastructures, which has caused confusion and tension across later debates about agricultural antibiotics through today. Future use of monensin for beef and milk production will depend on how experts distinguish ionophores from other antibiotics, the role of monensin as a methane inhibitor in the wake of the climate crisis, as well as its potential use for human medicine, including as a cancer treatment.