Effects of extruded corn on milk yield and composition and blood parameters in lactating dairy cows

According to a 2x2 cross over design, fourteen Holstein dairy cows at 99 +/- 55 DIM were fed two diets containing 21.5% DM of either ground corn (GC) or extruded corn (EC). Performance and metabolic profile were detected during the third week of each experimental period. DMI and milk yield were not affected by dietary treatments. Milk fat and protein percentage of EC diet were significantly (P < 0.10) lower than those of GC diet. Probably the higher rumen degradability of starch from EC thesis modified the synthesis of specific fatty acids leading to a milk fat depression event. Diets did not influence blood parameters, except for lower values of total protein and glucose content in EC diet-fed cows. Results suggested that the dietary inclusion of extruded corn should not be used at the tested level of substitution.