Relative bacterial densities throughout the intestine of beef cattle. Bacterial densities associated with mucosa (A) or within digesta were measured in the small and large intestine of beef cattle (log10 copy number μl-1 of template 16S rDNA). Treatments are cattle administered AS700 (black histograms) and cattle not administered antimicrobials (white histograms). Intestinal locations are: (1) duodenum; (2) proximal jejunum; (3) central jejunum; (4) distal jejunum; (5) ileum; (6) cecum; (7) spiral colon; (8) descending colon; and (9) rectum. Vertical lines associated with histograms indicate the standard error of the mean. Within A and B, histogram bars at each location not followed by the same letter differ (P < 0.05). Bars indicated by an asterisk differ (P < 0.001) between digesta and mucosa-associated at corresponding locations.