Fatty acid composition of pastures

Abstract

The long chain fatty acid (LCFA) concentration and composition of herbage from 3 mixed-species pastures grown at Kyabram, Victoria, were determined for a small number of samples harvested at a nominal grazing height. The 3 pasture types were perennial ryegrass (Lolium perenne L., 51-61%), Persian clover (Trifolium resupinatum L., 37-76%) and subterranean clover (Trifolium subterraneum L., 39-84%). Based on a small data set, we estimate that cows grazing perennial ryegrass, Persian clover or subterranean clover-type pastures could consume herbage containing 18-22, 14-27 and 20-34 g LCFA/kg DM, respectively, with half to two thirds of this as 18:3 fatty acid. Time of year appeared to be an important factor in determining the total concentration and composition of LCFA in pastures. There was a positive linear relationship between the total concentration of LCFA and concentration of crude protein in harvested herbage, with this relationship apparently independent of botanical composition of pastures.