West et al. (1997)) reported lower DMI and milk yield for cows fed diets in which T85 hay replaced 15 or 30% of the DM provided by corn silage or diets in which alfalfa hay replaced 15 or 30% of the DM provided by corn silage. Cows fed diets with 30% T85 hay accounted for the majority of the decline. These researchers also reported a tendency for reduced DMI as a percentage of BW for Holsteins fed T85 compared with AH. Dietary NDF concentrations increased as hay was added to the diet and the increase was greater with T85 hay compared with AH, resulting in average NDF intake of 1.80 and 1.49% of BW, respectively. Because NDF digestibility of T85 hay is higher than that of AH, NDF turnover is faster, which supports greater NDF intake (West et al., 1997). However, the rations in a previous trial (West et al., 1997) were not balanced for NDF concentrations or NDF digestibility, which differed across treatments. These factors exert confounding effects on DMI and milk yield; therefore, it is difficult to know whether responses in DMI and milk yield were due to differences in the fiber digestibility of forages alone, the filling effects from different NDF concentrations, or both (Oba and Allen, 1999).