Aspirin: a staple in nearly every medicine cabinet, the first line of defense against an oncoming headache. This familiar friend in human medicine, however, takes a complicated turn when we consider its use in veterinary medicine, particularly in livestock animals. This simple pain reliever raises complex questions about residual effects and potential risks that extend beyond the individual animal. Increased use of aspirin has captured the attention of the FDA as farmers use it to treat pyrexia and pain in dairy cattle infected with highly pathogenic avian influenza (HPAI). Thus, the seemingly straightforward question of using aspirin in cattle becomes a complex and multifaceted issue, highlighting the need for careful evaluation and adherence to strict guidelines to ensure both animal well-being and the safety of our food system.
In October 2024 the FDA issued a "Dear Veterinarian" letter, prohibiting the use of unapproved aspirin to treat fever and pain in lactating dairy herds. Previously, aspirin use was considered of "low regulatory concern," but increased use, particularly for HPAI treatment, and the risk of milk residues prompted this change. While technically "unapproved," aspirin was previously allowed for extralabel use under the Animal Medicinal Drug Use Clarification Act (AMDUCA). This raises the question of what "unapproved" yet legal means.
Dr. Alison Vander Plaats explained on the American Association of Bovine Practitioners (AABP)'s "Have You Herd?" podcast that drug approval requires manufacturers to prove safety and efficacy. Aspirin, along with other common farm drugs like lidocaine, epinephrine, and calcium solutions, lacks formal approval. Although ideal, the low revenue generated by these products makes the expensive approval process unrealistic for manufacturers. However, certain research indicates that the demonstrated effectiveness of aspirin could make the FDA approval process a worthwhile investment for manufacturers and potentially benefit consumers as well.
Recent studies have investigated the potential benefits of administering aspirin to postpartum cows, suggesting it may enhance their recovery and productivity. Two studies by Barragan et al. (2020, 2021) offered compelling evidence for the potential value of short-term aspirin use. Barragan et al. (2020) indicated a positive influence of aspirin on the metabolic status, production, and overall health of postpartum dairy cows. Additionally, Barragan et al. (2021) observed that aspirin use after calving reduced incidences of uterine diseases; this ultimately led to improvement in conception rates and reduced calving intervals. The benefits associated with aspirin use in dairy cattle, especially those in the transition stage, may add value to the idea of approaching the FDA approval process for the drug. However, while these studies show promising initial findings, more research is certainly necessary to exclude more information, such as optimal dose and long-term effects of use. Gathering additional information would serve in making a case for FDA approval and provide practitioners with evidence for using the product. Nonetheless, until aspirin receives FDA approval, and its benefits are conclusively validated by scientific research, it is advisable to follow the progress of ongoing studies rather than implement its use in dairy cattle.
— Hannah Jones