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Stable carbon isotope composition of perirenal adipose tissue fatty acids from Engadine sheep grazing either mountain or lowland pasture.
MedLine Citation:
PMID:  22021810     Owner:  NLM     Status:  Publisher    
To provide further insights into ruminant lipid digestion and metabolism, and into cis-9,trans-11 18:2 synthesis, 12 growing Engadine lambs grazing either mountain pasture (2250 m above sea level; n = 6) or lowland pasture (400 m above sea level; n = 6) were studied. Both pastures exclusively consisted of C(3) plants. Before the experiment, all animals grazed a common pasture for 6 weeks. Grasses and perirenal adipose tissues of the sheep were analyzed for fatty acids by gas chromatography. Stable carbon isotope ratios (δ(13)C values in ‰ vs. Vienna Pee Dee Belemnite standard) were determined in the composite samples by elemental analyzer-isotope ratio mass spectrometry. The δ(13)C of the individual fatty acids were measured by gas chromatography-combustion-isotope ratio mass spectrometry. The δ(13)C( )value of the entire mountain pasture grass was -27.5 (SD 0.31) while that of the lowland pasture grass was -30.0 (SD 0.07). This difference was reflected in the perirenal adipose tissues of the corresponding sheep (P = 0.03), even though δ(13)C values were lower in the animals than in the grass. The δ(13)C values for cis-9 16:1 and cis-9 18:1 in perirenal fat differed between mountain and lowland lambs (P < 0.05). The 16:0 in the adipose tissue was enriched in (13)C by 5‰ compared to the dietary 16:0, likely as a result of partly endogenous synthesis. The δ(13)C( )values of cis-9,trans-11 18:2 (cis-9,trans-11 CLA) in the adipose tissue were smaller compared to those of its dietary precursors, cis-9,cis-12 18:2 and cis-9,cis-12,cis-15 18:3; conversely, the δ(13)C( )values of trans-11 18:1 were not, suggesting that large proportions of perirenal cis-9,trans-11 18:2 were of endogenous origin and discrimination against (13)C occurred during Δ9-desaturation. The same discrimination was indicated by the isotopic shift between 16:0 and cis-9 16:1 in the mountain grazing group. Furthermore, the δ(13)C( )values of cis-9,trans-11 18:2 were smaller relative to the precursor fatty acids in the mountain lambs than in the lowland group. This result suggests a lower biohydrogenation extent in lambs grazing on mountain grass in comparison to those grazing on lowland grass. This was supported by the smaller cis-9,trans-11 18:2 concentrations in total fatty acids found in the adipose tissues of the lowland lambs (P < 0.001). The results of this study demonstrate that natural differences between δ(13)C values of swards from different pastures and the adipose tissue fatty acids could be used as tracers in studies of lipid metabolism in ruminants.
E K Richter; J E Spangenberg; H Willems; M Kreuzer; F Leiber
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-10-21
Journal Detail:
Title:  Journal of animal science     Volume:  -     ISSN:  1525-3163     ISO Abbreviation:  -     Publication Date:  2011 Oct 
Date Detail:
Created Date:  2011-10-24     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8003002     Medline TA:  J Anim Sci     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
ETH Zurich, Institute of Agricultural Sciences, Universitaetstrasse 2, CH 8092 Zurich, Switzerland.
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