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Effect of environmental factors and influence of rumen and hindgut bio-geography on bacterial communities in steers.

Romero-Pérez, G.A., Ominski, K.H., McAllister, T.A., and Krause, D.O. (2011). "Effect of environmental factors and influence of rumen and hindgut bio-geography on bacterial communities in steers.", Applied and Environmental Microbiology, 77(1), pp. 258-268. doi : 10.1128/AEM.01289-09  Access to full text


Faeces from cattle production are considered important sources of bacterial contamination of food and the environment. Little is known about the combined effects of arctic temperatures and fodder tannins on rumen and hindgut bacterial populations. Individual rumen liquor and rectal faecal samples from donor steers fed either alfalfa silage or sainfoin silage and water ad libitum, were collected weekly on the first three sampling days and fortnightly afterwards. Daily ambient temperature was registered and averaged to weekly mean temperature. Steers fed sainfoin silage had lower (P<0.05) concentrations of branched-chain volatile fatty acids (VFA) than those fed alfalfa silage. All VFA concentrations were higher (P<0.001) in rumen liquor samples than in faecal samples. The interaction of sample type x diet showed a significant effect (P<0.05) on the bacterial community proportions in phyla Proteobacteria and Verrucomicrobia. Ambient temperature had an indirect effect (P<0.05) on phylum Firmicutes, as it affected its proportional balance. Bacterial population diversity in samples appeared to decrease concurrently with the ambient temperature. Phyla Firmicutes explained the first principal component at 64.83 and 42.58% of the total variance in rumen liquor and faecal samples, respectively. Sample type had a larger effect on bacterial communities than diet and temperature. Certain bacterial populations seemed to be better adapted than others to environmentally adverse conditions such as lower access time to nutrients due to higher motility and rate of passage of digesta caused by extreme temperatures, or anti-microbials such as tannins, possibly due to an influence of their bio-geographical location within the gut.

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