Ruminal protozoal contribution to the duodenal flow of fatty acids following feeding of steers on forages differing in chloroplast content

S A Huws, M R F Lee, Alison H Kingston-Smith, Eun J Kim, M B Scott, J K S Tweed, N D Scollan

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11 Citations (Scopus)


Ruminant products are criticised for their SFA content relative to PUFA, although n-6:n-3 PUFA is desirable for human health ( < 4). Rumen protozoa are rich in unsaturated fatty acids due to engulfment of PUFA-rich chloroplasts. Increasing the chloroplast content of rumen protozoa offers a potentially novel approach to enhance PUFA flow to the duodenum and subsequent incorporation into meat and milk. We evaluated protozoal contribution to duodenal n-3 PUFA flow due to intracellular chloroplast content. A total of six Holstein × Friesian steers were fed, in a two-period changeover design, either straw:concentrate (S:C, 60:40; DM basis; S:C, low chloroplast) or fresh perennial ryegrass (PRG; high chloroplast). Following 12 d adaptation to diet, ruminal protozoal and whole duodenal samples were obtained. N and fatty acid content of whole duodenum and rumen protozoal samples were assessed and protozoal 18S rDNA quantitative PCR performed, enabling calculation of protozoal N flow. The ratio of individual fatty acids:N in rumen protozoal samples was calculated to obtain protozoal fatty acid flows. Based on total fatty acid flow, contribution (%) of protozoa to individual fatty acid flows was calculated. Protozoal fatty acid data and microscopical observations revealed that protozoa were enriched with 18 : 3n-3 following PRG feeding, compared with the S:C diet, due to increased intracellular chloroplast content. However, duodenal protozoal 18S rDNA concentration post PRG feeding was low, indicating rumen retention of the protozoa. Nutrition influences the 18 : 3n-3 content of protozoa; the challenge is to increase protozoal flow to the small intestine, while maintaining sustainable rumen densities.

Original languageEnglish
Pages (from-to)2207-14
Number of pages8
JournalThe British Journal of Nutrition
Issue number12
Publication statusPublished - 28 Dec 2012


  • Animals
  • Cattle
  • Chloroplasts
  • DNA, Protozoan
  • Diet
  • Duodenum
  • Fatty Acids
  • Male
  • Rumen
  • Comparative Study
  • Journal Article
  • Research Support, Non-U.S. Gov't


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