In North Vietnam, during winter, shortage of herbage constrains the profitability of dairy farming. The first objective of this study was to evaluate the potential of alternative temperate (C3) forage species, namely common oat (Avena sativa L.), lop-sided oat (Avena strigosa Schreb.), Italian ryegrass (Lolium multiflorum L.) and a commercial forage mixture (Avex), to address the shortage of herbage during winter in the mountain regions of North Vietnam. The second objective was to measure the effects of cultural practices (sowing rate, harvest interval and irrigation level) on yield of dry matter (DM), chemical composition, digestibility of DM and metabolizable energy (ME) concentration of herbage from the best adapted C3 species previously tested (lop-sided oat). Four experiments were conducted. Oat species proved to be the best adapted species and produced the highest annual yield of herbage (7600 kg DM ha)1) with a high nutritive value. Yields of DM of lop-sided oat were not affected by sowing rate of seed but increased as the length of harvest intervals increased from 30 to 45 and 60 d (P < 0Æ001). Crude protein concentration, digestibility ofDMand ME concentration decreased as the harvest interval increased (P < 0Æ01). Irrigation increased the yields of DM of lop-sided oats by 1Æ3 (P < 0Æ05) but had no effect on the nutritive value of herbage. It is concluded that both common oat and lopsided oat are suitable species to provide herbage in the winter for the mountain regions of North Vietnam.