The objective of this study was to measure the effects of giving hay as a supplement to cows grazing at two different daily herbage allowances. Pregnant, non-lactating Friesian cows were allocated to four treatments: low herbage allowance with hay (LA+) or wthout hay (LA); and high allowance with hay (HA+) 01 without hay (HA). Hay was fed at 5 kg DM/cow daily, and the two herbage allowances were 9 or 14 kg DM/cow daily. Supplementing with hay increased total dry matter (DM) intake, but decreased herbage DM intake at both allowances. The decreases in herbage intake were 0.26 and 0.40 kg herbage OM eaten per kg hay DM eaten, at the lower and higher allowances respectively. The corresponding values, expressed as MJ metabolisable energy (ME), were decreases of 0.44 and 0.65 MJME from herbage per MJME eaten as hay. The decreases in herbage intake resulted in increases in residual herbage yield at both allowances. The implications of these results for grazing management during the winter are brlefly discussed. Keywords: supplementary feeding, hay, substitution rate, condition score, dairy cattle.
