Many dairy production systems have require available sites to apply dairy slurry after spring planting and during the summer months. One potential option is to apply these nutrients on perennial grass sods; however, this approach is viable only if voluntary intake by livestock is not affected. Dairy slurry or commercial fertilizer were applied at rates that delivered 53 and 56 kg N/ha, respectively, to ‘Elsie' orchardgrass in early April, and immediately after second cutting. Orchardgrass from the first (14 May; early heading stage) and third (14 July; vegetative regrowth) cuttings was harvested as hay in 1.2 x 1.5-m round bales. Hays were offered to eight (483 ± 37.6-kg) Holstein heifers in (two) parallel Latin squares with a 2 x 2 factorial arrangement of treatments. Hays made from regrowth had numerically greater NDF (614 vs. 578 g/kg), and poorer 48-h NDF digestibility (671 vs. 725 g/kg NDF) than hays made from early-headed forage, while manured forages exhibited greater CP (164 vs. 134 g/kg) than commercially fertilized hays. Intakes of DM and organic matter (OM) were not affected by fertilization method or the interaction of main effects (P > 0.331), and intakes of NDF were not affected by any treatment factor (P > 0.111; mean = 11.9 g/kg BW). Intakes of DM (20.7 vs. 19.4 g/kg BW) and OM (18.7 vs. 17.2 g/kg BW) from early-headed hays were greater (P < 0.015) than regrowth; however, greater intakes of CP (P = 0.014), K (P = 0.002), Ca (P = 0.001), and Mg (P < 0.001) were observed for regrowth. Application of dairy slurry resulted in greater intakes of CP (P < 0.001), K (P = 0.002), and Mg (P = 0.002) than observed for commercially fertilized hays. Generally, intakes were primarily affected by harvest date, effects of frequent manuring were relatively minor.