A review of the most widely used medicinal plant active compounds and their effects on growth, health and production parameters in the poultry industry

Thymol, carvacrol, cineole, alpha-pinene, menthol, and menthone are among the most common and effective phenols and terpenes which are widely used in the livestock and poultry industry. These compounds are found in the essential oils of the plant belonging to the Lamiaceae family, especially thyme, mint, and rosemary. These compounds possess synergistic effects and appeared to be potent as an anti-oxidant, antibacterial, antiviral, anti-inflammatory, anti-depressant, and immunomodulatory agents. These bioactive compounds increase the digestive tract enzymes secretion and thereby improve digestion, activate variety of intestinal nutrient transport, inhibit oxidation processes, inhibit the growth of bacteria, fungi, and parasites in the digestive system, modulate the intestinal microbial population, and improve the immune system function in the livestock and poultry. These physiological mechanisms have led to the improvement of digestive function, growth performance, weight gain and feed conversion ratio, increased production, reduced mortality, improved production quality (taste, color, texture, shelf-life, biological value) and improved environmental conditions (reducing unpleasant smells and toxic gases) in the poultry and livestock. With regard to the mentioned beneficial impact of plant bioactive compounds in production and health of poultry and livestock animals, it is necessary to use these valuable resources to improve the production efficiency and reduce the use of chemical drugs in the livestock and poultry husbandry.