In the present study, miik yield was 2.13 kg/cow/day higher when cows were fed a 100% REC died, compared to cows fed only dry corn. The increase of of milk yield of cows 100% REC compared with cow fed only corn dry ground be attributed to a combination of increased digestibility of nutrients(starch and CP) and increased DMI,which corresponded an increased intake of 8.945 MJ NEL/cow/day. This extra NEL intake would support a maximum milk yield of2.8kg based on the average milk composition found in the present study(NRC, 2001) considering that actual milk yield increased by 2.1 kg/d cows fed 100% REC compared with cows fed only corn dry ground(Table 4), the remaining energy intake was probably used for weight gain. However, previous studies also reported no effect or even reduction ofmilkyield whenruminal degradability of corn was increased. For example, no effect of the source of corn starch in the diet(dry or high moisture corn) was found on milk yield of high producing dairy cows(average 41 kg/cowlday) (Bradford and Allen, 2004)on the other hand, Shabi et al. (1999) observed lower production(1.2 kg/cowlday) for dairy cows fed extruded corn grain than cows fed ground corn, even when corn starch digestibility was higher for diets with extruded corn. Different responses to ruminal degradability of corn starch suggest that other factors linked to ruminal health health may affect milk yield and compomposition