Diversity of bacterial communities isolated from the solid and liquid phase of the rumen of sheep fed diets of variable composition

The aim of this study was to analyze bacterial diversity in bacterial pellets isolated from the solid (SAB) and liquid (LAB) phase of the rumen in sheep fed different diets. Four rumen-fistulated sheep were fed 4 diets with forage:concentrate ratios (F:C) of 70:30 (HF) or 30:70 (HC) and either alfalfa hay or grass hay as forage (FOR). SAB and LAB were isolated from each sheep immediately before feeding, and the automated ribosomal intergenic spacer analysis (ARISA) of the 16S ribosomal DNA was used to analyze bacterial diversity. A total of 168 peaks were detected in the ARISA electropherograms across the total 32 bacterial pellets, with 6 peaks only found in SAB and 8 found only in LAB. The SAB isolated from sheep fed HF diets had greater number of peaks and Shannon index than those from sheep fed HC diets (P=0.03 and 0.05, respectively), and SAB from sheep fed grass hay diets had greater values of both parameters than those isolated from sheep receiving alfalfa hay diets (P=0.002 and 0.004). In contrast, LAB profile was not affected (P=0.23 to 0.65) by either F:C ratio or FOR. The results indicate that SAB are more markedly affected by dietary characteristics than LAB.