Influence of species, cutting date and cutting interval on the fatty acid composition of grasses

Two experiments were conducted to evaluate the effects of species, cutting date and cutting interval on the concentration of fatty acids in temperate grasses. The first experiment compared eight species, harvested in late autumn and summer. Levels of individual fatty acids were distinctive for some species, with low levels of C18:1 in Dactylis glomerata L. and high levels of C18:2 in Phleum pratense L. Differences in individual fatty acids could not be used to differentiate fescues and ryegrasses. However, fatty acid profiles could be used to differentiate species when material was managed similarly (i.e. at the same cut). There were large species x cut interaction effects, showing that management factors will be as important as plant breeding in manipulating fatty acid levels. Cultivars belonging to one Lolium perenne L. gene pool were identified as having significantly higher alpha -linolenic acid and total fatty acids in late-season (November) material. The second experiment compared three ryegrass species over a growing season, with three or five cuts. All species had high concentrations of fatty acids and a high proportion of or-linolenic acid during vegetative growth (late April). Fatty acid levels declined markedly in all species after this date, recovering by autumn. Kunth Lolium multiflorum Lam. and Lolium x boucheanum had higher levels of total fatty acids and alpha -linolenic acid in the early and late season when compared with perennial ryegrass. Fatty acid levels (particularly C18:2 and C18:3) declined when the regrowth interval was extended from 20 to 38 d. These studies demonstrate opportunities to change the composition of ruminant products through breeding and management of grasses for altered levels of fatty acids.