The objective of this work was to determine the in vitro effect of the propolis on the specific activity of ammonia production (SAAP) or activity deamination of amino acids and on ruminal fermentation in bovine. The SAAP was determined using ruminal fluid and McDougall buffer (1:4) with different levels of propolis extract and excess of hydrolyzed casein. In the study of the in vitro effect of the propolis on the ruminal fermentation and SAAP, four Holstein steers were used, in two experimental periods, fed a 35.0% concentrate diet and submitted to the control and propolis extract treatments. The propolis extract obtained with ethanol at 70% in water was in vitro more efficient than that obtained with ethanol at 99.5% in water. Values up to 78% of SAAP inhibition in relation to the control were obtained. The propolis extract did not affect dry matter intake, ruminal pH, ammonia and microbial protein concentrations. There were no differences for molar proportions of the volatile fat acid (VFA), acetic, propionic and butyric in the rumen fluid. However, the propolis extract increased the total VFA concentration as well as inhibited SAAP by the ruminal microorganisms, demonstrating that, in spite of not having reduced the ruminal ammonia level, it seems to exist potential of this effect to happen in other situations, as in diets with high rate of degradable protein/fermentable carbohydrate, observed in new grass pastures or grass pastures consociated with legumes.
ammonia; pH; protein; ruminal fermentation; VFA
