Twenty 'actannq Friesian cows with average live bocy weight ranging from
450 to 6:20 '<9 were 'JS ,,0 . All animals were in the 2^no to 4'h lactation season. ,';nimals
were ranccrruv oistrtbuteo into five similar groups(G) (four animals each ), :0 be fed
formulated expenrnerual rations which were as follows :G 1 Control 70 %
concentrate feed mixture (CFM) + 30 % rice straw (RS), G 2: ration 1 : 70 % CFM +
30 % ammoniated nee straw (ARS) + bentonite (B) , G 3 : ration 2: 65 % CFM +5%
ground corn grain (GCG) + 30 % ARS +B, G 4: ration 3 : 60 % CFM +10% GCG +
30 % ARS +B and G S: ration 4 : SS % CFM +1S% GCG + 30 % A.RS + B .These
proportions were chosen to achieve approximately isonitrogenous rations containing
about 12-13% CP. The results obtained showed that digestibility of OM was
significantly (P aigestibility was significantly (p < O.OS) higher with ration 4 than the other rations. The
digestibility of CP, NFc. NOF, hemi. and cell. were significantly (p < O.OS) higher when
animals were fed the control and ration 4 than the other rations, while the CF was
significantly (p < O.OS) improved with increasing the replacement of corn grains to the
highest level with ration 4. Nutritive values as total digestible nutrients (TON),
metabolizable energy (ME), net energy (NE) and relative feeding value RFV were
significantly (p < O.OS) higher with ration 4 than the other rations. Based on the mear.
value of ruminal pH. buffering capacity (BC), NH3.N concentration. the results showed
that ruminal pH was decreased (p < O. OS) when feeding ration 4 compared with ration 1
(7.09 and 7.38 .respectivety ) .The BC was higher (p < O.OS) when feeding ration 2 , 3
and 4 than the control or ration 1 . The NH3-N concentration was significantly (p < O.IJ5)
increased by the replacement with corn grains The VFA concentration was
significantly (p < O.OS) lower by increasing the replacement with corn grain in ration 3
and ration 4 than the other rations. The calculated effective neutral detergent fiber
(eN OF) values ranged from 39.41 to 46.1S with different rations. The lowest eN OF
value was recorded (p < O.OS) for ration 4 compared with the other ones.