Effects of oregano essential oil on the ruminal pH and microbial population of sheep

Abstract

Oregano essential oil (OEO), which has antimicrobial properties, may be used for altering the ruminal pH and microbial populations of sheep, as observed by the altered volatile fatty acid patterns. To further elucidate the effects of OEO on ruminal pH and microbial populations of sheep, 3 German merino sheep × local sheep crossbred rams with permanent ruminal fistulas were randomly assigned to a 3 × 3 Latin square design with 12-d periods. The treatments were as follows: control (CON); OEO4: OEO supplied at 4 g•d -1 ; and OEO7: OEO supplied at 7 g•d -1 . Starting on day 11, rumen fluid was collected at 0 h, and at 4, 8, 12, 24 and 48 h after supplying OEO, and then pH values of rumen fluid were immediately measured. The abundance of microbial populations was determined by using qPCR. The ruminal pH values were similar among the sheep from all treatments. The abundance of ruminal fungi was higher for the sheep supplied OEO7 compared with the sheep supplied CON and OEO4, especially at 4 and 12 h. The abundance of ruminal protozoa decreased with supplied OEO, indicating that OEO could inhibit the protozoa. The abundance of the total ruminal bacteria was similar for the sheep from all treatments, but R . flavefaciens , R . albus and F . succinogenes increased in the sheep supplied OEO4 compared with those in the sheep supplied CON, however, the sheep supplied OEO7 had higher abundances of R . flavefaciens than the sheep supplied CON. These results demonstrated that supplying OEO to sheep did not affect the ruminal pH but could shift the rumen microbial population to one with less protozoa. Supplying OEO can preferentially enhance the growth of certain rumen microbial populations, but the shifts were influenced by the supply rate. Therefore, supplying low amount (i.e. 4 g•d -1 ) of OEO could have positive effects on ruminal microbial populations, whereas supplying elevated doses of OEO could be detrimental to those same ruminal microbial populations.

Phytogenic Additives Can Modulate Rumen Microbiome to Mediate Fermentation Kinetics and Methanogenesis Through Exploiting Diet–Microbe Interaction

“…Supplementation of oregano EO at 4 and 7 g/d promoted the population of primary cellulolytic bacteria and ruminal fungi, respectively, in sheep ( 241 ). An in vitro study revealed that the inclusion of EO of S. spicatum in a high-concentrate diet significantly improved the rumen fermentation characteristics by reducing CH 4 and NH 3 -N while promoting propionate concentration ( 252 ).…”

Effects of Cornus and Its Mixture with Oregano and Thyme Essential Oils on Dairy Sheep Performance and Milk, Yoghurt and Cheese Quality under Heat Stress

“…Adding 1.25 g/kg DM of thyme essential oil improved both ruminal fermentation and nitrogen metabolism [ 48 ]. Another study investigating the effects of oregano essential oils on sheep showed an increase in the population of three primary cellulosic bacteria and ruminal fungi, affecting the rumen fermentation process [ 49 ]. However, potential toxic effects of plant essential oils are not scarce and should be taken into consideration before feeding them to animals [ 50 ].…”

Formulation and antimicrobial activity evaluation of a 0.2% chlorhexidine canine mouthwash with essential oils

“…The main components of OEO and TEO are carvacrol, thymol, and α-terpene (5). Carvacrol is a non-toxic monoterpene, widely studied for its pharmacological properties such as antibacterial and antifungal activities (12).…”

“…Chlorhexidine (CLX) is also on the list of the most used chemical agents due to its antibacterial action against a wide range of aerobic and anaerobic bacteria (4). Besides, oregano essential oil (OEO) and thymus essential oil (TEO) have been associated with an important antimicrobial activity against Gram-positive and Gram-negative bacteria due to the presence of carvacrol, thymol, and α-terpene (5).…”