Trabajo presentado al : Joint Annual Meeting. ADSA-ASAS. Orlando Florida (USA), julio, 2015. T485Fermenters are widely used to study ruminal fermentation, but
infonnation on microbial populations developing in fermenters over
the incubation period is limited. Four Rusitec fermenters were fed
2 diets representative of those administered to dairy sheep (DAI;
50:50 alfalfa hay:concentrate) and fattening lambs (FAT; 15:85 barley
straw:concentrate) in a crossover design with 2 14-d incubation periods to assess the evolution of the microbial populations. There were 4
fermenters per diet. The fermenters received daily 30 g of diet DM and
samples from liquid (LIQ) and solid (SOL) digesta were taken on d 3,
8 and 14, and stored frozen at-80ªC until DNA extraction. Concentrations ofbacterial and protozoal DNA and relative abundance offungi
and methanogenic archaea to total bacteria! DNA concentration were
detennined by real time PCR using previously validated primers and
DNA from bacteria and protozoa isolated from sheep rumen as standards. Data were analyzed as a mixed model with repeated measnres
using the PROC MlXED of SAS. The model included diet, incubation
nm, time, and diet x tin1e as fixed effects, and fermenter as a random
effect. Diet x sampling time interactions (P > 0.05) were detected for
bacteria! and protozoal DNA concentrations in both digesta phases. The
bacteria! DNA concentrations in SOL did not change (P = 0.002) over
the incubation period, whereas concentrations in LIQ increased (P <
0.001) by 1.5 and 1.8 times for DAI and FAT diets by the end ofthe
incubation, respectively. Protozoal DNA concentrations on d 14 were
37.8 and 8.0 times lower (P < 0.001; means across diets) than those on
d 3 for SOL and LIQ phases, respectively. Relative abundance offungi
decreased (P < 0.05) with time in both phases, and that ofmethanogenic archaea remain unchanged in LIQ and increased (P = 0.021) in
SOL. Concentration of bacteria! and protozoal DNA and the relative
abundance of methanogenic archaea were greater in the fermenters fed
the DAI diet (P < 0.05) compared with FAT diet. The results show that
microbial populations in Rusitec fermenters are affected by the incubated
diet and change over the incubation periodPeer reviewe
