Effect of Thyme Essential Oils (Thymus hyemalis and Thymus zygis) and Monensin on in Vitro Ruminal Degradation and Volatile Fatty Acid Production

Abstract

The effect of the essential oils of thyme on the in vitro ruminal degradability of a barley seed/alfalfa hay substrate was studied. Two essential oils were used, one from Thymus hyemalis (TH), rich in carvacrol, and the other from Thymus zygis (TZ), rich in thymol. Four experimental treatments of in vitro degradability, using the Daisy II(200/220) incubator, were conducted including a negative control (CO), a positive control at 7.5 microg/mL of monensin (MO), and two treatments with essential oils (TH or TZ) at 1.35 microL/mL. The material was incubated at 39.5 degrees C for various lengths of time. At each time, the disappearance of dry matter, crude protein, and neutral detergent fiber was measured. Volatile fatty acids (VFAs) were determined after 48 h of incubation. CO and MO provided (p < 0.01) higher values of potential degradability (a + b) of DM than the TH and TZ treatments (72.6 and 70.8 vs 53.2 and 48.2%, respectively). Also, crude protein degradability was lowest in the essential oil treatments. The CO treatment showed the highest potential degradability of NDF. The values of VFA production obtained (p < 0.001) with CO and MO treatments were higher than those obtained with TH and TZ treatments (21.0 and 19.1 vs 11.2 and 10.1 mM). The essential oils decreased the molar proportion of propionate, increasing the acetate/propionate ratio. In conclusion, the effects of essential oils at assayed doses would not be nutritionally beneficial to the ruminal energetic metabolism.

Potential of carvacrol to modify in vitro rumen fermentation as compared with monensin

“…On the other hand, M also revealed to reduce lactic acid producing bacteria such as Streptococcus bovis (McGuffey et al, 2001). In accordance with our results, Martínez et al (2006) reported that two essential oils of thyme at 1.35 ml/ml, one rich in carvacrol and the other in thymol, decreased the in vitro potential degradability of NDF (in our study the 250 and 500 mg/l concentrations were equivalent to 0.264 and 0.528 ml/ml of carvacrol).…”

Effects of essential oils from medicinal plants acclimated to Benin on in vitro ruminal fermentation of Andropogon gayanus grass

“…Of all EOs assayed, O. gratissimum appeared to be the most detrimental to rumen microbial activity with clear inhibition at dosages of 200–400 mg L −1 . Consistent with this study, Martinez et al observed a decrease in DMD of an alfalfa hay:barley grain mixture (30:70) using extracts from T. zygis at 1.35 mL L −1 . Inclusion of T. capitatus at dosages of 250–1000 mg L −1 also decreased DMD and GP (DM incubated basis) from an alfalfa hay:concentrate mixture (50:50) .…”

Effects of essential oils from African basil on fermentation ofAndropogon gayanusgrass in the Artificial Rumen (RUSITEC)

“…Thymus zygis, which contains mainly thymol (62.1%), also reduced DMD of a 30:70 alfalfa hay:barley grain mixture when included in batch cultures (Martinez et al 2006). Finally, Kamalak et al (2011) observed a decrease in true DMD of alfalfa hay with a reduction in true NDFD, total VFA and GP when 50 to 200 mg L (1 of thymol was added to batch cultures.…”