Eighteen lactating Friesian cows at different lactation seasons were taken
one month pre-partum and divided into 3 similar groups. (G1) control was fed 25%
corn silage (CS) on OM basis, (G2) was fed 50% corn silage and (G3) was fed 75%
corn silage. Results showed that silage fermentation characteristics (pH, TFVA,
ammonia nitrogen (NH3-N) and fractions of VFAs) were almost within the normal
ranges reported for good quality silage. Also, it was indicated that increasing level of
CS in rations significantly (P<0.05) increased pH and decreased VFAs and NH3-N in
rumen liquor. Cows in G3 showed the highest average daily milk yield (ADMY)
followed by G2 and G1 at all lactation periods. Maximum ADMY was observed
between 30 and 60 days of lactation period in all groups. Milk fat content showed
inconsistent trend in all groups and showed the maximum fat content at 60 days of
lactation period. Protein content showed the highest values at the beginning of
lactation, thereafter decreased in all groups. Lactose content was almost higher in G3
and G2, than G1 at all lactation times. As a results of increasing fat, protein and
lactose contents in milk in G2 and G3 total, solids content was higher in G3 and G2,
respectively at all lactation times. Total concentrations of TVFA, NCN, NPN were
significantly not affected by feeding treatments.