Comparison of the fatty acid composition of fresh and ensiled perennial ryegrass (Lolium perenne L.), affected by cultivar and regrowth interval

Two experiments were conducted to evaluate the effects of grass cultivar and regrowth stage on the fatty acid (FA) profile in fresh and ensiled perennial ryegrass (Lolium perenne L.). The Experiment 1 compared the composition of fresh grass with that of pre-wilted ensiled material of six cultivars, harvested after 25 days of regrowth at a dry matter (DM) yield of approximately 2000 kg DM ha−1. The Experiment 2 compared fresh and ensiled grass of two cultivars, harvested after 23 and 33 days of regrowth. There were genetic differences in fatty acid profiles in fresh grass, but the physiological basis of these differences was not clear as management, growth conditions and leaf blade proportion were similar among cultivars. The concentrations of most FA declined with increasing regrowth stage. In fresh grass, 98% of the fat was present as esterified fatty acids (EFAs) but in silages, 27–73% of the total FA consisted of free fatty acids (FFAs). The largest changes in FA contents took place in the EFA. In pre-wilted ensiled grass, the contents of most FA were lower than in fresh grass, especially of C18:1 and C18:3.