Licorice (Glycyrrhiza glabra) root is a perennial herb which has a long history of use in ancient Assyrian, Egyptian, Chinese, and Indian cultures. It is sold as a dietary supplement for digestive and respiratory issues and bacterial and viral infections. It also often an ingredient in some products for topical use.
Licorice root is sold as a powder, extract, or in capsules. Potential side effects of licorice root, if given in large amounts or over a long period of time include increased blood pressure and decreased potassium levels. These effects may be a concern for birds with heart or kidney disease.
Specific applications studied in poultry include:
Antiviral: Licorice possesses some antiviral activity in vitro toward a number of viruses---including Newcastle disease virus (NDV) in chickens and Duck Hepatitis Virus (DHV) in ducks. In a study conducted on 40 day-old white Pekin domestic ducklings, treatment with glycyrrhizin alone or with DHV vaccine demonstrated to be an effective immune system booster and had an antiviral effect against DHV.
Gut health: Adding licorice extract to the diet at 1 g/kg of diet improved the growth performance of broiler chickens, as well as influenced the maintenance of intestinal integrity and reduced Campylobacter jejuni shedding from infected birds. (D Ibrahim et al., 2020)
