Influence of cultivar and cutting date on the fatty acid composition of perennial ryegrass (Lolium perenne L.)

Two experiments were conducted to evaluate the effects of cultivar and season on the fatty acid (FA) composition of the lipids of perennial ryegrass (Lolium perenne L.). Eight diploid cultivars were cut at the same target yield of approximately 2000 kg dry matter ha^?1 between mid‐June and mid‐September. Two cultivars (Barlet and Magella) were harvested during four 2‐week periods and six cultivars (AberGold, Respect, Agri, Herbie, Barezane and Barnhem; cultivars 1–6) during three periods. The concentrations of individual FA were determined by gas chromatography. Barlet had higher concentrations of linolenic acid (C18:3) than Magella, but lower concentrations of linoleic acid (C18:2). Cultivars 1–6 were more variable in their leaf blade and stem proportions than Barlet and Magella. Despite this, there was no difference between cultivars 1–6 in the FA composition of the herbage. On average 0·74 of the FA consisted of C18:3. Higher concentrations of total FA were found in mid‐summer than in early summer. This was related to a high leaf blade proportion in the herbage, indicating that the proportion of leaf and stem of the herbage probably had more effect on lipid concentrations than the season per se in this period. However, in late August and mid‐September, the total FA concentration declined whereas the leaf blade proportion increased. Therefore, in this period environmental factors appeared to have a modifying effect. As consistent differences in the concentration of C18:3 were found among cultivars Barlet and Magella throughout the season, these studies demonstrate opportunities to change the composition of ruminant products through the choice of cultivars of perennial ryegrass.