الفهرس 
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Abstract
ABSTRACT
This work was staged into two studies. The in vitro study was conducted to investigate the effects of different doses (0, 30, 50, 100, and 200 mg/L of culture fluid) of thymol (THY), cinnamaldehyde (CIN) or their mixture (MIX) with 80:20 concentrate: forage diet. While, the in vivo experiment was carried out to evaluate the effect of supplementation of MIX at 100 and 200 mg/kg ration on lambs performance. The results of the in vitro study indicated that different doses of THY, CIN and MIX significantly reduced cumulative gas production with 200 mg/L of THY. The maximum reduction of CH4 production was observed with THY at 200 mg/L (56.18%) followed by MIX at 50 mg/L (25.78%) and CIN at 100 and mg/L (23.17 and 23.40%, respectively). Concentration-dependent increase in pH values were recorded with all treatments. The ammonia nitrogen (NH3-N) was markedly lowered with all high concentration of tested compounds while in vitro dry and organic matter disappearance were not affected. Different doses of THY, CIN or MIX had no effect on total volatile fatty acids (TVFAs) concentration. Nevertheless, the proportions of acetate and propionate were significantly decreased only with MIX at 200 mg/L and THY at 200 mg/L, respectively in comparison with the control group.
In the second experiment, Addition of MIX tended to improve nutritive values (TDN, DCP, SE), dry matter intake, average daily gain and feed efficiency. Ruminal pH, TVFAs concentrations and NH3-N concentration were similar between lambs fed MIX and those fed the control diet. Mean number of protozoa concentration was not altered in response to any of MIX levels. Serum concentrations of glucose, cholesterol, triglyceride, urea-N, ALT and AST were not changed by MIX addition. In conclusion, the first experiment results revealed that using moderated doses of THY, CIN and their mixture with high concentrate diets did not affect rumen fermentation and DM degradation adversely but have good anti-methanogenic activity which would promote its potential use in sheep diets in moderate doses. The second experiment results suggested that supplementing growing lambs fed high concentrate diet with MIX may have limited potential to improve their growth rate and feed efficiency without any detrimental effect on ruminal and blood constituents.