This experiment had as objective to evaluate protein fermentation of three nitrogen sources (trypticase, soybean meal and fish meal), with or without monensin or propolis extract addition. Incubations were done by using 7.2 mL of McDougall buffer, 2.0 mL of inocula, 0.2 mL of ethanolic solution with or without monensin or propolis and 84.4, 150 or 112.5 mg/10 mL of trypticase, soybean meal and fish meal, respectively, in a 3x3 factorial arranjement. The flasks were incubated anaerobically at 39ºC in water bath during 120 hours, and samples were collected from the media over time for ammonia, microbial protein, soluble protein and protein degradability determinations. Fish meal caused lesser ammonia production than trypticase and soybean meal in control treatment, due to its lower degradability. Monensin and propolis decreased ammonia production in the trypticase and soybean meal treatments, leading to accumulation of soluble protein in the media. The microbial protein synthesis was similar among the three feed sources and with presence or absence of inhibitors, except in the case of propolis that estimulated synthesis in the fish meal treatment. There was greater protein degradability of the control treatment for soybean meal (73%) than fish meal (42%). Monensin reduced degradation of trypticase and soybean meal, by inhibiting ammonia production, and propolis increased degradation of fish meal, by increasing soluble protein concentration in the media. Due to the in vitro effect of propolis on fermentation activity, it is necessary to carry out researches in order to verify its effect on ruminal fermentation and animal performance.
ammonia; feeds; ionophores; microorganisms; propolis; rumen
