摘要：Fecal bacteria in Hokkaido native horses were enumerated by their morphology and Gram staining, and then three major cellulolytic species were quantitated by recently developed competitive polymerase chain reaction (cPCR) assays. Fecal bacterial flora in horses showed drastic change between grazing on summer grassland pasture and grazing on winter woodland pasture mainly consisting of bamboo grass (Sasa nipponica). The number of total bacteria was decreased in winter samples, accompanied with a higher proportion of Gram negative rods and lower proportions of Gram negative cocci, Gram positive rods and cocci than those in summer. This high proportion of Gram negative rods was partly explained by the high cPCR-assay values for Fibrobacter succinogenes (a highly cellulolytic Gram negative rod) in winter samples. Of three major cellulolytic bacterial species, F. succinogenes was dominant in feces of Hokkaido native horses regardless of the sampling season. Feces of light horses mainly come from Thoroughbreds which had been kept with Hokkaido native horses, were taken in winter and employed for analysis. All three cellulolytic species were much less dominant in light horses. These results suggest that F. succinogenes contributes to fiber digestion in the hindgut of Hokkaido native horses, especially in winter woodland pasture where bamboo grass (Sasa nipponica) is mainly available.
