The objective of this study was to quantify amino acid (AA) profiles in plasma collected from dairy heifers grazing swards containing ryegrass/clover, chicory and plantain in autumn and spring. The study comprised a 28-day autumn trial and a 21-day spring trial using 56 Friesian x Jersey heifers. Total AA concentrations ranged from 2849 to 3165 μM in autumn and from 3195 to 3454 μM in spring, with no treatment effect. Season affected essential AA (EAA) and total AA concentrations. Total plasma AA concentrations were lower in autumn (2965 μM) than in spring (3303 μM). Based on these results, feeding dairy heifer’s either pure chicory, binary mixture or pure plantain does not affect EAA and total AA of Friesian x Jersey heifers. Further, no relationship was established between AA and weight gain of heifers in this study.