Ruminal bacteria and protozoa composition, digestibility, and amino acid profile determined by multiple hydrolysis times

S. W. Fessenden, T. J. Hackmann, D. A. Ross, A. Foskolos, M. E. Van Amburgh

Research output: Contribution to journalArticlepeer-review

13 Citations (SciVal)
132 Downloads (Pure)


Microbial samples from 4 independent experiments in lactating dairy cattle were obtained and analyzed for nutrient composition, AA digestibility, and AA profile after multiple hydrolysis times ranging from 2 to 168 h. Similar bacterial and protozoal isolation techniques were used for all isolations. Omasal bacteria and protozoa samples were analyzed for AA digestibility using a new in vitro technique. Multiple time point hydrolysis and least squares nonlinear regression were used to determine the AA content of omasal bacteria and protozoa, and equivalency comparisons were made against single time point hydrolysis. Formalin was used in 1 experiment, which negatively affected AA digestibility and likely limited the complete release of AA during acid hydrolysis. The mean AA digestibility was 87.8 and 81.6% for non-formalin-treated bacteria and protozoa, respectively. Preservation of microbe samples in formalin likely decreased recovery of several individual AA. Results from the multiple time point hydrolysis indicated that Ile, Val, and Met hydrolyzed at a slower rate compared with other essential AA. Singe time point hydrolysis was found to be nonequivalent to multiple time point hydrolysis when considering biologically important changes in estimated microbial AA profiles. Several AA, including Met, Ile, and Val, were underpredicted using AA determination after a single 24-h hydrolysis. Models for predicting postruminal supply of AA might need to consider potential bias present in postruminal AA flow literature when AA determinations are performed after single time point hydrolysis and when using formalin as a preservative for microbial samples.

Original languageEnglish
Pages (from-to)7211-7226
Number of pages16
JournalJournal of Dairy Science
Issue number9
Early online date28 Jun 2017
Publication statusPublished - 01 Sept 2017


  • amino acid
  • digestibility
  • hydrolysis
  • ruminal bacteria
  • ruminal protozoa


Dive into the research topics of 'Ruminal bacteria and protozoa composition, digestibility, and amino acid profile determined by multiple hydrolysis times'. Together they form a unique fingerprint.

Cite this