Use of high pressure liquid chromatography (HPLC) for the determination of cda-tocopherol levels in forage (silage/grass) samples collected from different regions in Ireland

First, second and third cut grass silage samples were collected from eight regions around Ireland (184 samples in total) and analysed for vitamin E content. Fresh grass samples were also collected at one site in Co. Cork and analysed for α-tocopherol content. The concentration of α-tocopherol [μg/g dry matter (DM)] was determined using high performance liquid chromatography analysis. A wide variation in α-tocopherol levels in silage samples was found. α-Tocopherol levels in first, second and third cut silage samples ranged from 4.9 to 20.8, 4.4 to 13.0 and 1.3 to 3.9 μg/g DM, respectively. The mean values of α-tocopherol in first, second and third cut silage samples were 11.3±0.9, 9.7±0.7 and 2.3±0.5 μg/g DM, respectively. There was no significant difference in α-tocopherol levels between first and second cut silage samples. However, third cut silage samples had significantly (P<0.05) less α-tocopherol compared to first and second cut samples. There was no decrease in α-tocopherol levels in silage samples following storage at -20°C for 2 months. Fresh grass samples were classified as pasture grass, meadow grass (consisting of 20% Bromus spp and 80% Holcus spp, hedgerow grasses (predominately Dactylis glomerata L.) and white or red clover. Pasture grass had significantly (P<0.05) higher α-tocopherol levels than other grass types analysed. Meadow grass had significantly (P<0.05) higher α-tocopherol levels than clover or hedgerow grasses. α-Tocopherol concentration in the different grass types decreased in the order: pasture grass>meadow grass>hedgerow>white clover>red clover.