Antibiotics in Animal Husbandry: The Efficacy and Safety of Available Alternative Treatments Are Being Evaluated

With the aim of reducing the use of antibiotics in farm animals, the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) has published an overview of alternative solutions and raises the question of granting these products a specific status at the European level, without classifying them as veterinary medicinal products. Based on an evaluation of scientific publications, its expert report identifies a large number of molecules, plants, plant extracts, and microorganisms used in this field, while highlighting the heterogeneity of the available data regarding their safety, efficacy, and their potential to select for resistant bacteria. Further studies are needed in each relevant animal sector to resolve these uncertainties. As part of the fight against antimicrobial resistance, ANSES was tasked with identifying all products currently used as alternatives to antibiotics (for both curative and preventive treatment of animal diseases) and evaluating their efficacy and safety for humans, animals, and the environment, following a review of the existing literature. This inventory covers more than 220 commercial substances and preparations that claim to have a direct or indirect effect in limiting the use of antibiotics in livestock (ruminants, poultry, pigs, rabbits, and fish). The most frequently cited commercial preparations primarily contain plants, essential oils, probiotics, organic acids, and/or fatty acids. Most of the claims made relate to digestive function (67% of indications concern balancing or restoring the gut microbiota), regardless of the animal species (with the exception of fish). Pigs are the primary target for these products (69 out of a total of 150 mentions, or nearly 50%), followed by ruminants (less than 20% of the total, with nearly two-thirds concerning cattle and one-third concerning goats). Poultry, including both laying hens and broiler chickens, rank third in terms of citations, followed by rabbits. The number of commercial preparations intended for fish and crustaceans remains limited in this survey. It should be noted that horses were included in the analysis regarding rhodococcosis in foals (promising hyperimmune plasma) and diarrhea in adult horses, given the widespread use of antibiotics to treat these diseases. The evaluation of the efficacy and safety of all these products was conducted based on the available scientific literature, through a review of scientific publications. The heterogeneity and variability of the collected data constituted a limitation of this evaluation method; however, it may be used in the future by industry associations to assess new scientific studies or research yet to be published. One of the risks associated with the use of these products concerns their potential (or lack thereof) to promote antibiotic resistance. At present, this aspect has been studied only to a limited extent, but the risk is not zero, particularly for organic acids (used as biocides), probiotics, or bacteriophages.  

According to ANSES, “post-authorization monitoring should be implemented, and it should be possible to monitor resistance in environmental microbiota.”

  In its conclusions, ANSES also recommends initiating a review to identify, within each relevant animal production sector, the priority classes of alternatives that require in-depth studies—particularly epidemiological ones—in order to resolve doubts regarding their efficacy and safety, using appropriate methods. Currently, the various existing product families appear to have weaker effects than those of antibiotics. This poses a challenge for experimental research, which—to ground its findings on solid scientific foundations—will need to adapt its protocols to detect “low-intensity effects.” Furthermore, prior to conducting research and experiments, the report emphasizes the importance of determining the legal status of these products, as this will make it possible to define the necessary studies, as well as the conditions under which they must be conducted, prior to their market authorization and use. This consideration must be framed within a European context, given the origin of the regulatory frameworks governing both animal feed and veterinary medicinal products. ANSES therefore recommends raising the issue of the legal status of these substances at the European level, as part of the plan to combat antibiotic resistance, “so that the relevance and feasibility of creating a specific status for products that achieve antibiotic use reduction—without classifying them as veterinary medicinal products—can be examined.”