Turkey tail mushroom (Trametes versicolor) is increasingly used in pet supplements, particularly for dogs, due to its purported immune-supporting and anti-cancer properties. The primary scientific justification for its use comes from studies examining its beta-glucan content, which can modulate immune system activity. Notably, a small but well-conducted clinical trial at the University of Pennsylvania in 2012 evaluated the effects of a turkey tail mushroom extract (PSK) in dogs with hemangiosarcoma, a highly aggressive cancer. The study found that dogs receiving the mushroom extract had longer median survival times compared to historical controls, although the study size was limited.

Additional laboratory and animal research has identified anti-inflammatory, anti-viral, and potential anti-tumor effects attributed to polysaccharide compounds in turkey tail. However, large-scale, randomized, controlled trials in companion animals are lacking, and most evidence remains preliminary or extrapolated from human or in vitro studies. Turkey tail is also used as an adjunct in traditional Asian medicine, but its use for pets is a more recent development driven by emerging scientific interest rather than long-standing tradition.

In summary, there is moderate scientific evidence (rated 3/5) supporting the use of turkey tail mushroom as an adjunctive therapy, especially for immune support and cancer care in pets. While promising, further rigorous studies are needed to confirm efficacy and safety for broader veterinary use.