Throughout the experiment each of the 4 treatment groups grazed separately, with the 4 groups grazing in close proximity to each other. A flexible rotational grazing system was adopted in which each treatment group was given access to fresh herbage daily, following the p.m. milking. A key grazing management target was that pre- and postgrazing sward heights were similar with all treatments (target of 5.5 cm), with this relatively high postgrazing sward height chosen so that herbage intakes would not be restricted with any treatment. This residual sward height was initially targeted by providing daily herbage allowances of approximately 16, 14, 12, and 10 kg of DM/cow per day for concentrate treatments 2.0, 4.0, 6.0, and 8.0 kg/d, respectively. However, these herbage allowances were reduced as the study progressed, and adjustments in daily herbage allowances were made between treatments, so as to maintain the target residual sward heights.