In vitro Effect of Essential Oils on Rumen Fermentation and Microbial Nitrogen Yield of High Concentrate Dairy Cow Diet
Present study was conducted to investigate the effect of including plant essential oils on in vitro ruminal fermentation and microbial nitrogen synthesis of a dairy cow diet rich in concentrate. The treatments consisted of the diet alone (control; BD) as well as containing 50 and 100 μl L-1 essential oil of thyme (BDT), mint (BDM), savory (BDS), or a mixture of the essential oils at the rate of 1:1:1 (BDmix). Essential oils decreased gas production at 24, 48 and 96 h of incubation compared with that of BD. However, mint at the rate of 50 or 100 μl L-1 resulted an increase in the microbial nitrogen when compared to BD, BDS and BDT. The nitrogen content of truly undegraded residu (NDFN) content and NH3-N concentration were lower, while the dry matter digestibility was greater in the BDmix, regardless of dosage levels, as compared with the control. The inclusion of a mixture of essential oils at 50 μl L-1 to the basal diet caused intensified dry matter disappearance, in comparison to other treatments. Results showed that the synergetic effects of essential oils together in a dairy cow diet of rich in concentrate can alter rumen microbial fermentation and improve microbial protein yield.