557 Ruminal microbiology from Nellore steers supplemented with additives in the rainy season

The aim of study was evaluate the ruminal microbiology from animals fed supplements with monensin (MN), virginiamycin (VM) or both associated (MNVM), in the rainy season. Twelve steers cannulated in the rumen (518.42 ± 55.40 kg) were housed in 12 paddocks (one animal on each paddock) ofBrachiariacv.'Xaraés' and supplemented daily with 0.3% of BW. The diets were: supplement without additives (SUPL), with MN (80 mg/kg), with VM (150 mg/kg) and associated supplement MNVM (80 + 150 mg/kg of MN and VM, respectively). The experiment consisted of four periods of 28 d (27 d of adaptation and 1 d of sampling collection). Animals were housed continuously in the paddocks with animals used in a trial for performance evaluating. The study evaluated the relative proportion of microorganism,R. albus, R. flavefaciens, F. succinogenes, S. ruminantiumand methanogenic bacteria on 28th and 118th d of the experimental period (1stand 4thperiod). This design chosen to show the effect in the short and long term antibiotics. Data were analyzed as a completely randomly design with three replicates by treatment on each period, using the MIXED procedure of SAS. In the first period, theR. albusand methanogenics groups had no effect (P>0.05) by the use of the two additives. Observed the effect (P<0.05) of VM and MNVM on the relative proportion ofR. flavefaciens, F. succinogenesandS. ruminantium, however, theR. flavefaciensbacteria did not differ from the control group to MN. In the 4th period the relative proportion ofF. succinogenes, S. ruminantiumincrease when used VM and MNVM. The relative proportion ofR. flavefaciensdid not differ when compared to control group with used MN, however there was decrease the proportion with used VM and MNVM (P <0.05). The methanogenic group showed effect when used VM (P<0.05). In this study, the virginiamycin had greater control overR. flavefaciens, it is worth noting that the adaptive effect of bacteria was not conserved when the same additive was used.