Effects of essential oils from Rosmarinus officinalis and Thymus capitatus on in vitro rumen fermentation in sheep
2013
N., Moujahed | Y., Bouaziz | A., Khelfa
This study aimed to evaluate the effects of increasing doses (0, 5, 10, 20 and 40μl per 50 ml of buffered rumen fluid) of essential oils (EO) extracted by steam distillation from the leaves and twigs of rosemary (Rosmarinus officinalis) and thyme (Thymus capitatus)on in vitrogas production and the fermentation characteristics. Doses of EO were added to 500 mg of a diet composed of 50 per cent of rye-grass hay and 50 per cent of concentrate on dry matter (DM) basis. The medium of incubation consisted on ruminal liquid extracted from 2 cannulated sheep, mixed in equal proportions with a buffer solution introduced in 100 ml glass syringes (39 degrees C). At 24 h of incubation gas production was measured and part of the liquid was collected for analysis of ammonia nitrogen (NH3-N). Volatile fatty acid (VFA) concentration was calculated on the basis of total gas production. Rosemary EO had no effects, neither on total gas production nor VFA accumulation. However, at 24 h of incubation, rosemary EO increasedNH3-N concentration (P less than 0.001) when administered at the doses of 20 and 40 μl. Thyme EO decreased (P less than 0.0001) gas production starting from 10 μl dose. An increase (P less than0.001) of NH3-N concentration was recorded from the low dose of thyme EO, while the medium and high doses declined (P less than 0.001) NH3-N concentration. VFA concentration decreased linearly from 5 μl to 40 μl doses of thyme EO. Medium doses from thyme EO might reduce carbohydrate fermentation and protein deamination. It was concluded that the EO from thyme have a more drastic antibacterial effect on rumen fermentation than those from rosemary.
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