Characterization of the microbial community and pattern of ruminal fermentation of Angus and Nellore cattle during adaptation to diets with high energy content with different nutritional strategies

The objective of this study was to evaluate the effect of different nutritional strategies during the adaptation and finishing period on ruminal fermentation patterns and microbial community of cannulated Angus and Nellore cattle. Four 30-mo-old Nellore and four 30-mo-old Angus steers were used, with an initial body weight of approximately 450 kg which was divided into two 4 x 4 Latin squares. Each square was composed of animals of the same breed. The periods were divided as follows: 14 days of adaptation diet (5 days of adaptation 1 - 65% concentrate, four adaptation days; 2 - 70% concentrate and five adaptation days; 3 - 75% concentrate) and 18 days of finishing diet (80% concentrate). The diets provided differed only concerning the corn grain processing method and the presence or absence of sodium monensin. The treatments were as follows: FG(+)- Finely ground corn + monensin (27ppm); FG(-)- Finely ground corn HM(+)- High moisture corn + monensin (27ppm) HM(-)-High moisture corn. The study lasted 158 days, in which animals were submitted to four experimental periods (32 days each one) and three washout intervals (7 days) between periods 1 and 2, 2 and 3, and 3 and 4. Angus had higher consumption on days 12 and 16 when compared to Nellore (P=0.02). Angus cattle the lowest pH and the higher ruminal temperatures. Nellore breed had higher Shannon diversity than(P=0.007). Nellore showed a higher community of Butyrivibrio, Clostridiales and Prevotella(P<0.01) than Angus. During the transition period ruminal fermentation pattern and bacteria community are different for Angus than Nellore cattle. (AU)