QUANTIFICATION AND CHEMICAL-COMPOSITION OF MIXED BACTERIA HARVESTED FROM SOLID FRACTIONS OF RUMEN DIGESTA, EFFECT OF DETACHMENT PROCEDURE

Four ewes were given two diets made up with two ratios of rolled barle y grain and ammonia treated straw (80/20, diet C and 20/80 diet R) twi ce a day. Two microbial markers, purine bases (PB) and N-15, were used as internal and external markers, respectively. Ruminal bacteria from the liquid (LAB) and solid (SAB) fractions of digesta were harvested from samples obtained at 1 and 6 h after feeding. Bacteria were separa ted from the particulate material by cooling plus homogenisation (B) a nd also by applying tertiary butanol (TB), methylcellulose (M) or chan ges of temperature (CHT). The most effective procedures to remove bact eria from the solid phase were M and CHT although CHT showed the highe st level of losses and the lowest total recovery of the bacterial pell et. There were no differences between B and TB in both detaching effic iency and total recovery ratio of adherent bacteria. Ratio of recovery of detached material as a bacterial pellet was 32.0, 32.2, 33.3 and 2 7.8% for B, TB, M and CHT, rzspectively.:Diet did not interact with de taching efficiency of the experimental treatment although concentratio n of total N (g/100 OM) and PB (mu mol/g OM) content concentration wer e higher in pellets obtained with diet C (9.11 and 125) than with R (8 .20 and 107, respectively, P < 0.05). Postprandial differences were no t significant. Bacterial samples extracted from the liquid phase conta ined significantly (P < 0.001) more total N (9.21 vs. 8.51) PB (160.5 vs. 104.3) and PB/N (1.73 vs. 1.23 mu mol/mg) than those samples extra cted from the solid phase. There were no differences in the chemical c omposition of the microbial sample after detachment by B, BT and M but bacterial extract obtained after CHT treatment showed significant cha nges in PB, N content and PB/N ratio (P < 0.01). (C) 1998 Elsevier Sci ence B.V.