Veterinary probiotics and prebiotics have mixed evidence, speaker warns; commercialization and regulation are hurdles

Dr. Marcio Costa of the University of Montreal reviewed the state of microbial supplements in animals, arguing that while supplements can modulate the microbiome, evidence quality and commercialization barriers limit near-term alternatives to antibiotics in production systems.

Costa said probiotics remain the most used supplements but that the literature is inconsistent and subject to publication bias: "Probiotics are for sure the most used. However, the evidence that they work is weak," he said, adding that veterinary products are often poorly regulated and may not contain viable organisms claimed on the label or may even carry antimicrobial-resistance genes.

He distinguished prebiotics as fermentable fibers that can modulate bacterial populations but warned they lack specificity and can increase potentially harmful species. Costa also described experimental and field examples—high-dose zinc oxide in piglets produced large microbiome separations and postbiotic or phytogenic additives reduced intestinal lesions in experimentally infected chickens.

On commercialization, Costa said developers face regulatory obstacles for non-conventional or genetically modified strains and limited industry appetite to invest in strains isolated from animals. He cautioned that some advanced microbiome restoration treatments are costly (roughly $20,000 per treatment in contexts he cited), making such approaches prohibitive at farm scale.