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Evaluation of the ruminal bacterial diversity of cattle fed diets containing citrus pulp pellets

Broadway, P. R., Callaway, T. R., Carroll, J. A., Donaldson, J. R., Rathmann, R. J., Johnson, B. J., Cribbs, J. T., Durso, L. M., Nisbet, D. J., Schmidt, T. B.
Agriculture, food and analytical bacteriology 2012 v.2 no.4 pp. 297
Bacillus (bacteria), Butyrivibrio, Carnobacterium, Catonella, Dialister, Eubacterium, Prevotella, bacteria, cattle feeding, cattle feeds, citrus pulp, diet, essential oils, heifers, microbial ecology, pellets, population growth, rumen, rumen bacteria, species diversity
Variations to dietary components cause shifts in the ruminal microflora that can affect animal health and productivity. However, the majority of these changes, especially in terms of quantitative changes, have not been elucidated. Therefore, the objective of this study was to analyze the diversity of bacterial populations in the rumen of cattle fed various amounts of citrus pulp pellets (CPP). Heifers (n=18; 298.7±5.1 kg) were randomly assigned to 1 of 3 treatment diets (n=6/diet) containing CPP (0, 10, or 20%). Using bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP), the ruminal microbiota was examined to understand how different concentrations of CPP affected ruminal microbial ecology. The Firmicutes:Bacteroidetes ratio tended to increase (P = 0.07) in heifers fed CPP compared to controls. Specifically within the Firmicutes, Butyrivibrio and Carnobacterium populations increased in number with increasing amounts of CPP in the diet. In contrast, a linear decline (P = 0.009) in the population of Dialister and Catonella occurred with increasing CPP concentrations. Bacteria in the genera of Prevotella and Eubacterium were observed to be the predominant bacteria that populated the rumen (34% and 6%, respectively) in control heifers. An increase (P = 0.04) in the proportion of Bacilli bacteria in the ruminal microflora was associated with increases in dietary CPP. Overall, there were relatively few changes observed in ruminal microbial populations, thus highlighting the functional flexibility of the rumen and demonstrating that feeding CPP at rates up to 20% does not adversely impact ruminal microbial ecology. The lack of major changes in ruminal microflora may possibly be due to a lack of essential oils in the CPP utilized in the current study which may play a greater role in the alteration of ruminal microbial populations and may also explain the lack of an apparent effect in the current study as compared to previously reported studies.