Effect of different levels of yeast in comparison with monensin on the ruminal fermentation parameters and protein degradability in high concentrate diets

This study aimed to investigate the effect of different levels of yeast and monensin in high concentrate diets on the ruminal fermentation parameters by in vitro gas production method and protein degradability by in situ nylon bag technique. Experimental treatments included control diet (75% concentrate and 25% alfalfa) and supplemented control with three levels of yeast (2.5, 5, and 7.5 g per kg dry matter of diet) and three levels of monensin (15, 30, and 45 mg per kg dry matter of diet). The results showed that the addition of yeast in contrast to monensin resulted in a significant increase in cumulative gas production and the potential of gas production (b) (P<0.05). Ammonia nitrogen content was significantly decreased by adding different levels of monensin compared with the control treatment (P<0.05). Also, the average of short-chain fatty acids was significantly increased by adding yeast compared with the control treatment and different levels of monensin (P<0.05). The rumen degradable protein and its fractional degradation rate were significantly reduced by monensin supplementation (P<0.05). Based on the results of this study it can be suggested that the addition of 5 g yeast and 30 mg monensin (per kg DM) in high concentrate diets can improve ruminal fermentability and organic matter digestibility of feed and increase the accessibility of animal to diet energy.