Impact of Essential Oils Blend on Methane Emission, Rumen Fermentation Characteristics and Nutrient Digestibility in Barki Sheep

Abstract

In vitro and in vivo experiments were conducted to investigate the potential impacts of different levels of essential oils blend (EOB 0, 400, 800 ?l/kg of total mixed ration) on total gas and methane production, as well as on rumen fermentation parameters and nutrient utilization. The in vitro assay was carried out using semi-automatic system of gas production (GP) technique. In vivo evaluation was performed using 12 mature male Barki sheep (39±3.13 kg live body weight) randomly allocated into three groups. First group (control, n=4) was fed a basal diet, the second group (EOB0.5, n=4) was fed the basal diet supplemented with 0.5 ml of EOB/head/d, while the third group (EOB1.0, n=4) received the basal diet plus 1.0 ml of EOB/head/d. The investigation included mixture of commercial essential oils (EO) by equal proprotions e.g., eucalyptus (Eucalyptus globules), cinnamon (Cinnamomum cassia), peppermint (Mentha piperita), thyme (Thymus vulgaris) and lemon (Citrus limon),. The chemical profiles of individual and EOB were analyzed by GC/MS. The GC/MS results revealed that the cinnamic aldehyde (100%), 1,8-cineole (95.0%), thymol (39.4%), menthol (38.6%) and dl-limonene (88.6%) were the main components in EOs of cinnamon, eucalyptus, thyme, peppermint and lemon, respectively. There were no significant effects among investigated levels of EOB on in vitro GP and methane production, short chain fatty acids (SCFA), NH3-N concentration and protozoa count. The truly degraded organic and dry matter slightly decreased at the highest concentration of EOB tested. In vivo inclusion of EOB0.5 had no significant effect on dry matter intake (DMI) compared to EOB1.0 and untreated animals. Dry and organic matter digestion coefficients were not affected by EOB supplementation, while the digestion coefficients of crude protein (CP) decreased (P<0.05) with treatments compared to the control group. Supplementation of EOB0.5 increased (P>0.05) neutral detergent fiber (NDF) digestion compared to EOB1.0 and control group. Acid detergent fiber (ADF) digestion coefficient was not affected by the treatments. Total digestible nutrients (TDN) and digestible crude protein (DCP) were not affected by EOB treatments. There were no significant effects of both doses of EOB supplementation on N-balance, rumen pH, SCFA or NH3-N concentration. It can be concluded that EOB0.5 decreased CP digestion in sheep without positive impacts on other nutrients utilization and ruminal fermentation patterns, which may be related to the additive effects of the combination of EO and inadequate dose supplementation in the sheep diets.