The hydrogenation of dietary unsaturated fatty acids by the ruminant

Abstract

SummaryGoats were fed alfalfa meal containing 10% cottonseed or linseed oil. After 11 weeks the fatty acids of rumen, stomach, and caecum contents were compared to those of the feed.It was found that the high levels of linoleic and linolenic acis of the feed were reduced to very low levels in the rumen, with comparable increases in the saturated acids. Monoethenoid acids were increased after linseed oil ingestion and in one animal after cottonseed oil ingestion.The ratio of monoethenoid to saturated acids in the rumen fat was lower than in the endogenous fat of nonruminant animals. This explains the paradox of the low ratio in the depot fat of ruminants even after the ingestion of highly unsaturated fats.

Glyceride Hydrolysis and Glycerol Fermentation by Sheep Rumen Contents

“…On the gas chromatograms their methyl esters appeared in positions between methyl laurate and methyl tridecanoate, and between the latter and methyl myristate. Whilst the studies of Shorland et al (1957) showed that unsaturated fatty acids as such were hydrogenated when they were incubated with rumen contents, the experiments so far described here do not preclude the possibility that hydrogenation might take place whilst the acids were still in glyceride combination. Though in most of the experiments with linseed oil hydrolysis was almost complete, in others (as previously mentioned) ,the extent of hydrolysis was much less.…”

“…It should be mentioned that hydrogenation results in the production of spatial and positional isomers of unsaturated acids (Shorland et al 1957); these are included, where appropriate, in Tables 2 and 3 under the heading 'C,8 mono-, di-and tri-unsaturated acids'. Linolenic acid forms a very large proportion of the total fatty acids of pasture grasses (Garton, 1960).…”

“…This effect was attributed to hydrogenation of double bonds by rumen micro-organisms and was substantiated by comparisons of the unsaturation of feed lipids with that of the lipids of rumen contents in sheep (Shorland, Weenink & Johns, 1955) and goats (Reiser & Reddy, 1956) and the detailed examination of the products of incubation of oleic, linoleic and linolenic acids with sheep rumen contents (Shorland, Weenink, Johns & McDonald, 1957). In all the foregoing studies the total lipid of rumen contents was saponified before determination of the unsaturation of the component fatty acids.…”

Lipid metabolism in the rumen: New insights on lipolysis and biohydrogenation with an emphasis on the role of endogenous plant factors

“…BH intermediates of LNA were first observed by Reiser (1951), who found that after linseed oil was incubated with rumen sheep liquor, the LNA concentration decreased while the proportion of C18:2 and C18:1 increased. Shorland et al (1955) subsequently observed that the depot fat of grazing ruminants had a FA profile low in LNA, which is the main FA in grass.…”

CLAs, nature, origin and some metabolic aspects

“…Later, it was reported that biohydrogenation occurs in the rumen. Unsaturated fatty acids were reported to be transformed in less unsaturated fatty acids with trans double bonds [4,5]. In 1967, Kepler [6] reported that a ruminal bacteria, Butyrivibrio fibrisolvens, was able to produce conjugated 18:2 from linoleic acid.…”