Lipolysis and hydrogenation in the rumen

Two important activities of the rumen micro- organisms are (1) lipolysis of the lipids containing esterified fatty acids that are ingested by the ruminant and (2) hydrogenation of unsaturated fatty acids Comparisons of the fatty acid composition of the free fatty acids and the esterified lipids of rumen contents suggest that hydrogenation ofthe fatty acids does not occur until they are hydrolysed from glycerolipid (Garton, Lough & Vioque, 1961; Hawke & Robertson, 1964; Patton & Kesler, 1967). For example, Patton & Kesler (1967) found that the fatty acids of neutral lipids, polar lipids and free fatty acids isolated from the rumen contained 6-6, 7-1 and 70.0% of stearic acid respectively, whereas the same fractions