Low Ruminal pH Reduces Dietary Fiber Digestion via Reduced Microbial Attachment

  • Sung, Ha Guyn (School of Agricultural Biotechnology, College of Agriculture and Life Sciences Seoul National University) ;
  • Kobayashi, Yasuo (Graduate School of Agriculture, Hokkaido University) ;
  • Chang, Jongsoo (Department of Agricultural Science, Korea National Open University) ;
  • Ha, Ahnul (School of Agricultural Biotechnology, College of Agriculture and Life Sciences Seoul National University) ;
  • Hwang, Il Hwan (School of Agricultural Biotechnology, College of Agriculture and Life Sciences Seoul National University) ;
  • Ha, J.K. (School of Agricultural Biotechnology, College of Agriculture and Life Sciences Seoul National University)
  • Received : 2006.08.07
  • Accepted : 2006.10.11
  • Published : 2007.02.01


In vitro rumen incubation studies were conducted to determine effects of initial pH on bacterial attachment and fiber digestion. Ruminal fluid pH was adjusted to 5.7, 6.2 and 6.7, and three major fibrolytic bacteria attached to rice straw in the mixed culture were quantified with real-time PCR. The numbers of attached and unattached Fibrobacter succinogenes, Ruminococcus flavefaciens and Ruminocococcus albus were lower (p<0.05) at initial pH of 5.7 without significant difference between those at higher initial pH. Lowering incubation media pH to 5.7 also increased bacterial numbers detached from substrate regardless of bacterial species. Dry matter digestibility, gas accumulation and total VFA production were pH-dependent. Unlike bacterial attachment, maintaining an initial pH of 6.7 increased digestion over initial pH of 6.2. After 48 h in vitro rumen fermentation, average increases in DM digestion, gas accumulation, and total VFA production at initial pH of 6.2 and 6.7 were 2.8 and 4.4, 2.0 and 3.0, and 1.2 and 1.6 times those at initial pH of 5.7, respectively. The lag time to reach above 2% DM digestibility at low initial pH was taken more times (8 h) than at high and middle initial pH (4 h). Current data clearly indicate that ruminal pH is one of the important determinants of fiber digestion, which is modulated via the effect on bacterial attachment to fiber substrates.


Bacterial Attachment;Fiber Digestion;pH;Fibrobacter succinogenes;Ruminococcus flavefaciens;Ruminocococcus albus


Supported by : Agricultural R & D Promotion Center


  1. Cheng, K. -J., J. P. Fay, R. E. Howarth and J. W. Costerton. 1980. Sequence of events in the digestion of fresh legume leaves by rumen bacteria. Appl. Environ. Microbiol. 40:613-625.
  2. Hu, Z. -H., H. -Q. Tu and R. -F. Zhu. 2005. Influence of particle size and pH on anaerobic degradation of cellulose by rumen microbes. Int. Biodeter. Biodegr. 55:233-238.
  3. Koike, S. and Y. Kobayshi. 2001. Development and use of competitive PCR asays for the rumen cellulolytic bacteria: Fibrobacter succinogenes, Ruminococcus albus and Ruminococcus flavefaciens. FEM Microbiol. Letters. 204:361- 366.
  4. Latham, M. J., B. E. Brooker, G. L. Petipher and P. J. Harris. 1978. Ruminoccocus flavefaciens cell coat and adhesion to cotton cellulose and cell leaves of perennial ryegrass. Appl. Environ. Microbiol. 35:156-165.
  5. Miron, J., D. Ben-Ghedalia and M. Morrison. 2001. Invited Review: Adhesion mechanisms of rumen cellulolytic bacteria. J. Dairy Sci. 84:1294-1309.
  6. Mould, F. L., E. R. Orskov and S. O. Mann 1984. Associative effects of mixed feeds. I Effects of type and level of supplementation and the influence of the rumen pH on cellulolysis in vivo and dry matter degradation of various roughages. Anim. Feed Sci. Technol. 10:15-20.
  7. Mourino, F., R. Akkarawongsa and P. J. Weimer. 2001. Initial pH as a determinant of cellulose digestion rate by mixed ruminal microorganisms in vitro. J. Dairy Sci. 84:848-859.
  8. Pell, A. N. and P. Schofield. 1993. Microbial adhesion and degradation of plant cell walls. pp. 397-423 in Forage Cell Wall Structure and Digestibility. ASA-CSSA-SSSA, Madison, WI.
  9. Russell, J. B. and J. L. Rychlik. 2001. Factors that alter rumen microbial ecology. Sci. 292:1119-1122.
  10. Slyter, L. L. 1986. The ability of pH-selected mixed ruminal microbial population to digest fiber at various pHs. Appl. Environ. Microbiol. 52:390-391.
  11. Srinivas, B. and U. Krishnamoorthy. 2005. Influence of diet induced changes in rumen microbial characteristics on gas production kinetics of straw substrates in vitro. Asian-Aust. J. Anim. Sci. 18:990-996.
  12. Tajima, K., R. I. Aminov, T. Nagamine, H. Matsui, M. Nakamura and Y. Benno. 2001. Diet-dependent shifts in the bacterial population of the rumen revealed with real-time PCR. Appl. Environ. Microbiol. 67:2766-2774.
  13. Weimer, P. J. 1996. Why don't ruminal bacterial digest cellulose faster? J. Dairy Sci. 79:1496-1502.
  14. Craig, W. M., G. A. Broderick and D. B. Ricker. 1987. Quantitation of microorganisms associated with the particulate phase of ruminal ingesta. J. Nutr. 117:56-64.
  15. Morris, E. J. 1988. Charateristics of the adhesion of Ruminococcus albus to cellulose. FEMS Microbiol. Letters. 51:113-117.
  16. Roger, V. R., G. Fonty, S. Komisarczuk-Bondy and P. Gouet. 1990. Effects of physicochemical factors on the adhesion to cellulose avicel of the rumen bacteria Ruminococcus flavefaciens and Fibrobactor succinogenes subsp. succinogenes. Appl. Environ. Microbiol. 56:3081-3087.
  17. Bonhomme, A. 1990. Rumen ciliates: Their metabolism and relationships with bacteria and their hosts. Anim. Feed Sci. Technol. 30:203-266.
  18. Stewart, C. S., S. H. Duncan and H. J. Flint. 1990. The properties of forms of Ruminococcus flavefaciens which differ in their ability to degrade cotton cellulose. FEMS Microbiol. Lett. 72:47-50.
  19. Khampa, S., M. Wanapat, C. Wachirapakorn, N. Nontasol, M. A. Wattiaux and P. Rowlison. 2006. Effect of leve;s of sodium DL-malate supplementation on ruminal fermentation efficiency of concentrates containing high levels of cassava chip in dairy steers. Asian-Aust. J. Anim. Sci. 19:368-375.
  20. Gong, J. and C. W. Forsberg. 1989. Factors affecting adhesion of Fibrobacter succinogenes S85 and adherence defective mutants to cellulose. Appl. Environ. Microbiol. 55:3039-3044.
  21. SAS (Statistical Analysis System Institute). 1989. SAS/STATTM User's Guide: Statistics, Version 6, 4th Edition. Vol. 2, Cary, NC.
  22. Bhat, S., R. J. Wallace and E. R. Orskov. 1990. Adhesion of cellulolytic ruminal bacteria to barley straw. Appl. Environ. Microbiol. 56:2698-2703.
  23. Mould, F. L. and E. R. Orskov. 1983. Manipulation of rumen fluid pH and its influence on cellulolysis in sacco, dry matter degradation and the rumen microflora of sheep offered either hay or concentrate. Anim. Feed Sci. Technol. 10:1-14.
  24. Bae, H. D., T. A. McAllister, E. G. Kokko, F. L. Leggett, L. J. Yamke, K. D. Jakober, J. K. Ha, H. T. Shin and K. J. Cheng. 1997. Effect of silica on the colonization of rice straw by ruminal bacteria. Anim. Feed Sci. Technol. 65:165-181.
  25. Cheng, K. -J., C. S. Stewart, D. Dinsdale and J. W. Costerton. 1984. Electron microscopy of bacteria involved in the digestion of plant cell walls. Anim. Feed Sci. Technol. 10:93-120.
  26. Forsberg, C. W. and R. Lam. 1977. Use of adenosine-5- triphosphate as an indicator of the microbial biomass in rumen contents. Appl. Environ. Microbiol. 33:528-534.
  27. Sung, H. G., D. M. Min, D. K. Kim, D. Y. Li, H. J. Kim, S. D. Upadhaya and J. K. Ha. 2006. Influence of transgenic corn on the in vitro rumen microbial fermentation. Asian-Aust. J. Anim. Sci. 19:1761-1768.
  28. McDougall, E. I. 1948. Studies on ruminant saliva. 1. The composition and output of sheep's saliva. Biochem. J. 43:99-109.
  29. Russell, J. B. and D. B. Wilson. 1996. Why are cellulolytic bacteria unable to digest at low pH? J. Dairy Sci. 79:1503-1509.
  30. Pan, J., S. Koike, T. Suzuki, K. Ueda, Y. Kobayashi, K. Tanaka and Okubo. 2003. Effect of mastication on degradation of orchardgrass hay stem by rumen microbes: fibrolytic enzyme activities and microbial attachment. Anim. Feed Sci. Technol. 106:69-79.
  31. Akin, D. E. and F. E. Barton. 1983. Rumen microbial attachment and degradation of plant cell walls. Fed. Proc. 42:114-121.
  32. Koike, S., J. Pan, Y. Kobayashi and K. Tanaka. 2003. Kinetics of in sacco fiber-attachment of representative ruminal cellulolytic bacteria monitored by competitive PCR. J. Dairy Sci. 86:1429- 1435.
  33. McAllister, T. A., H. D. Bae, G. A. Jines and K. -J. Cheng. 1994. Microbial attachment and feed digestion in the rumen. J. Anim. Sci. 72:3004-30018.
  34. Minato, H., M. Mitsumori and K. J. Cheng. 1993. Attachment of microorganisms to solid substrates in the rumen. pp. 139-145 in Proc. Mie bioforum on Genetics, Biochemistry and Ecology of Lignocellulose Degradation. Uni Publisher, Tokyo.
  35. Morris, E. J. and O. J. Cole. 1987. Relationships between cellulolytic activity and adhesion to cellulose in Ruminococus albus. J. Gen. Microbiol. 133:1023-1032.
  36. Purdy, K. J., T. M. Embley, S. Takii and D. B. Nedwell. 1996. Rapid extraction of DNA and RNA from sediments by novel hydroxyapatite spin-colum method. Appl. Environ. Microbial. 62:3905-3970.
  37. Grant, R. J. and S. J. Weidner. 1992. Digestion kinetics of fiber: Influence of in vitro buffer pH varied within observed physiological range. J. Dairy Sci. 75:1060-1068.
  38. Kobayashi, Y., S. Koike, H. Taguchi, H. Itabashi, Dong K. Kam and J. K. Ha. 2004. Recent advances in gut microbiology and their possible contribution to animal health and production-Review. Asian-Aust. J. Anim. Sci. 17:877-884.
  39. Miron, J. and C. W. Forsberg. 1998. Features of Fibrobacter intestinalis DR7 mutant which is impaired with its ability to adhere to cellulose. Anaerobe 4:35-43.

Cited by

  1. Effects of Methylcellulose on Fibrolytic Bacterial Detachment and In vitro Degradation of Rice Straw vol.26, pp.10, 1970,
  2. Use of Real-Time PCR Technique in Studying Rumen Cellulolytic Bacteria Population as Affected by Level of Roughage in Swamp Buffalo vol.58, pp.4, 2009,
  3. Metagenomic analysis of Surti buffalo (Bubalus bubalis) rumen: a preliminary study vol.39, pp.4, 2012,
  4. Ruminal fermentation and microbial ecology of buffaloes and cattle fed the same diet vol.83, pp.12, 2012,
  5. Molecular analysis of the bacterial microbiome in the forestomach fluid from the dromedary camel (Camelus dromedarius) vol.40, pp.4, 2013,
  6. Dry chemical processing and ensiling of rice straw to improve its quality for use as ruminant feed vol.45, pp.5, 2013,
  7. Effects of replacing barley grain with graded levels of wheat bran on rumen fermentation, voluntary intake and nutrient digestion in beef cattle vol.94, pp.1, 2014,
  8. Characterization of the cellulolytic bacteria communities along the gastrointestinal tract of Chinese Mongolian sheep by using PCR-DGGE and real-time PCR analysis vol.31, pp.7, 2015,
  9. An Investigation into Rumen Fungal and Protozoal Diversity in Three Rumen Fractions, during High-Fiber or Grain-Induced Sub-Acute Ruminal Acidosis Conditions, with or without Active Dry Yeast Supplementation vol.8, pp.1664-302X, 2017,
  10. Alterations in ruminal bacterial populations at induction and recovery from diet-induced milk fat depression in dairy cows vol.101, pp.1, 2018,
  11. Volatile fatty acids and methane production from browse species of Algerian arid and semi-arid areas vol.46, pp.1, 2018,
  12. Comparative effects of grain source on digestion characteristics of finishing diets for feedlot cattle: steam-flaked corn, barley, wheat, and oats vol.98, pp.4, 2018,
  13. Rumen-buffering capacity using dietary sources and in vitro gas fermentation vol.58, pp.5, 2018,
  14. Expression of a Recombinant Lentinula edodes Xylanase by Pichia pastoris and Its Effects on Ruminal Fermentation and Microbial Community in in vitro Incubation of Agricultural Straws vol.9, pp.1664-302X, 2018,
  15. Improving ruminal fermentation and nutrient digestibility in dairy steers by banana flower powder-pellet supplementation vol.58, pp.7, 2018,