Rumen protozoa are rich in polyunsaturated fatty acids due to the ingestion of chloroplasts.
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.
Huws
Sharon A
SA
Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Gogerddan, Aberystwyth SY23 3EB, UK.
Kim
Eun J
EJ
Kingston-Smith
Alison H
AH
Lee
Michael R F
MR
Muetzel
Stefan M
SM
Cookson
Alan R
AR
Newbold
Charles J
CJ
Wallace
R John
RJ
Scollan
Nigel D
ND
D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D056890:Eukaryota / Q000235:genetics / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D008297:Male; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012417:Rumen / Q000382:microbiology*
D004269:DNA, Bacterial; D016054:DNA, Protozoan; D005231:Fatty Acids, Unsaturated; D012336:RNA, Ribosomal, 16S; D012337:RNA, Ribosomal, 18S; D002734:Chlorophyll