Glyceride Hydrolysis and Glycerol Fermentation by Sheep Rumen Contents

Abstract

Microbial hydrolysis of triglycerides was observed when these were incubated anaerobically at 37[degree] with sheep rumen contents. The extent of hydrolysis was variable, but was often considerable (> 90%) when linseed oil was used as substrate. The free fatty acids liberated were analysed by gas chromatography and, as compared with the acids present initially in glyceride combination, they were less unsaturated because of microbial hydrogenation. Linolenic acid was particularly effectively hydrogenated. No synthesis of long-chain fatty acids took place during the incubations and, apart from the possibility that in some experiments a limited conversion of stearic acid to palmitic acid took place, there was no evidence of significant degradation of long-chain acids. Glycerol liberated during the hydrolysis was completely metabolized, in part to volatile fatty acids, largely propionic acid. No mono- or diglycerides was detected as intermediates in the lipolysis of triglycerides. Analysis of the contents of the rumen, abomasum and small intestine of each of two slaughtered sheep, one of which had previously been fed on a diet rich in linseed oil, showed that most of the total higher fatty acids present in each of these three portions of the alimentary tract was in the form of free acids. It is concluded that microbial lipolysis results in the pre-digestion of much of the lipids ingested by the sheep as part of its feed.