Thyme essential oil for sheep: Effect on rumen fermentation, nutrient digestibility, nitrogen metabolism, and growth

Abstract

Two experiments were conducted to evaluate the effect of thyme (Thymus vulgaris) essential oil (EO) doses on rumen fermentation, nutrient digestibility, and nitrogen metabolism, as well as performance and coccidia oocyst discharge. In experiment I, 20 rumen-cannulated wethers received the experimental diets containing 80% dry matter (DM) of haylage and 20% DM of concentrate. Treatments were 25mg of monensin/kg DM or doses of 1.25, 2.50, or 3.75g of thyme EO/kg DM. In experiment II, 50 ewe lambs received the same diets from experiment I, including a diet without feed additives. Wethers fed with diets containing 1.25g/kg DM of thyme EO had higher molar proportion of propionate (P= 0.03) and butyrate (P< 0.01), and lower (P= 0.04) acetate to propionate ratio than other treatments. Adding thyme EO to diets increased (P= 0.02) nitrogen retention compared to monensin. The performance of ewe lambs was not affected (P≥ 0.05) by treatments. However, lambs fed monensin had a lower (P= 0.04) number of coccidia oocyst discharge than others. Adding 1.25g/kg DM of thyme EO in high-forage diet improved ruminal fermentation. Thyme EO enhanced nitrogen metabolism, however, it did not improve performance.