Effect of free thymol and sustained release thymol on rumen fermentation and plasma metabolites in sheep

This experiment was conducted to compare the effect of free and sustained release thymol on rumen fermentation characteristics, microbial protein and some plasma metabolites. Six ruminally cannulated sheep were used in a 3×3 merged Latin square design. Treatments were (a) basal diet+ 250 mg free Thymol, (b) basal diet+ 250 mg slow relrase Thymol and (c) control (basal diet without Thymol). The experiment consisted of three 14-d periods with 10 d adaptation and 4 d sampling. At sampling period, the feces were collected and at the end of each period blood sampling and rumen fluid collection were made at different times. The measured traits were: Feed digestability, NNH3, plasma and glucose concentration, ruminal pH, microbial protein synthesis and efficiency of microbial protein synthesis. Dry matter intake (985.5 g and 917.5 g per day, respectively), crude protein digestibility (82.7% and 85.6%, respectively) and plasma glucose (114.8 mg/dL and 108 mg/dL, respectively) were increased by free and sustained release thymol consumption (P<0.05). Plasma urea concentration, microbial protein synthesis and N-NH3 were decreased in 5 and 7 hours after feeding (P<0.05). Number of diplodinia was 0.38 105 in diet with free thymol and this number was lower than those in other two treatments (P<0.05). Thymol consumption improved the efficiency of dietary protein utilization by decreasing N-NH3 and increased level of plasma glucose showed a positive effect on energy utilization of animal.