A 2016 study utilizing Turkish Origanum minutiflorum (containing 81.69% carvacrol) set out to determine if synergistic activity existed between Oregano Essential Oil (OEO) and Monensin (MON), an antibiotic used to control parasitic disease in chickens. Although no synergism was shown to exist between the two, this study revealed substantial improvements in the digestive capabilities and overall gut health of chickens fed the oregano essential oil.
In this study, the formation of the bird’s intestines were improved by the addition of Oregano Essential Oil. Higher, longer and wider villi, as well as decreased crypt depth were observed in the duodenum, jejunum, and ileum areas of the intestines, "providing a greater surface area for nutrient digestion and absorption." These improvements contributed to "increased mucosal enzymes, absorption, and the efficiency of the nutrient transport system."
The digestive enzyme activities, in both the pancreas and small intestine, significantly increased in chickens fed oregano oil; therefore, it was shown that OEO may provide a progressive effect on the "quality of the intestines, secretion of digestive enzymes, and particularly the antioxidant defense potential against parasitic infections."
Also noteworthy was the lowering of the oxidative stress marker, Malondialdehyde (MDA), as well as a significantly higher antioxidant defense activity (SOD - Superoxide dismutase), indicating that the plant bioactives in oregano oil have antioxidant properties capable of reducing the harmful effects of oxidation, thus improving the overall condition of the birds.
The contained plant bioactives found in Origanum minutiflorum helped to establish "microbial balance throughout the intestines, enhanced nutrient utilization and gut passage rates (motility), as well as encouraged endogenous digestive enzymatic activity", resulting in an overall "increased intestinal absorptive surface area."1)