As part of the management of intensive grazing, the focus on simple and productive forage systems has led to a limited range of plants being used in grazing swards supported by high levels of chemical fertilisers. This study investigated three different combinations of plant diversity and N fertiliser level (perennial ryegrass monoculture (PRG), 250 kg N ha–1; two-species perennial ryegrass-white clover (PRG-WC), 125 kg N ha–1; eight-species containing grasses, clovers and herbs (MSS), 125 kg N ha–1). Each sward type had its own farmlet of 20 paddocks and comprised 50 dairy cows on 20 ha which were rotationally grazed. Over two years, botanical composition of the PRG-WC was composed of 836, 163 and 1 g (kg DM)–1 of grasses, white clover and unsown species, respectively; MSS had 673, 151, 171 and 5 g (kg DM)–1 of grasses, clovers, herbs and unsown species respectively. Total net herbage production (13 022 kg ha–1 year–1 of DM forage) and nutritive values were unaffected by sward type during the 2 years. These results suggest that increasing sward diversity while reducing the use of chemical N fertiliser can maintain herbage production and nutritive value.