Rumen protozoa are rich in polyunsaturated fatty acids due to the ingestion of chloroplasts

Sharon A. Huws, Eun J. Kim, Alison H. Kingston-Smith, Michael R. F. Lee, Stefan M. Muetzel, John A. Cookson, Charles J. Newbold, R. John Wallace, Nigel D. Scollan

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35 Citations (Scopus)


Within this study, we investigated whether the polyunsaturated fatty acids (PUFA)-rich nature of rumen protozoa is a consequence of ingestion of PUFA-rich chloroplasts. Four Hereford x Friesian steers were offered hay [low 18:3 (n-3) and low chlorophyll concentration] followed by freshly cut perennial ryegrass [high 18:3 (n-3) and high chlorophyll concentration] for 16 days. On the 14th and 16th days, rumen protozoa as well as attached and planktonic bacteria were fractionated 1 h before (-1 h), 2 and 6 h postfeeding, and their fatty acid concentrations determined. Protozoa fractionated from fresh grass-fed steers were richer (P < 0.05) in PUFA, except conjugated linoleic acid, for all time points compared with those from hay-fed steers. Protozoal density was higher (P < 0.05) for grass compared with hay. Entodinomorphid abundance was 3.4 times higher on fresh grass (P < 0.01) compared with hay. Confocal microscopy and transmission electron microscopy confirmed that Epidinium spp. were commonly saturated with intracellular cytoplasmic chloroplasts. These data suggest that engulfment of chloroplasts is a major contributor to the high 18:3 (n-3) concentration of protozoa.

Original languageEnglish
Pages (from-to)461-471
Number of pages11
JournalFEMS Microbiology Ecology
Issue number3
Early online date5 Jun 2009
Publication statusPublished - Sept 2009


  • rumen protozoa
  • planktonic and attached bacteria
  • fatty acid
  • chloroplast
  • DGGE
  • QPCR
  • conjugated linoleic-acid
  • water-soluble carbohydrate
  • vaccenic acid
  • chemical-composition
  • bacterial fraction
  • ruminal bacteria
  • lolium-perenne
  • duodenal flow
  • stearic-acid
  • dairy-cows


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