The effect of substitution of concentrate feed mixture (CFM) by yellow corn fed
along with ammoniated nce straw plus bentonite ration of lactating cows on their
performance for milk yield and composition as well as blood metabolities was
investigated. Twenty lactating rriesian cows with body weight ran~ing from of 450 to
620 kg werE used in this study. All animals were in the 2nd to 4t lactation season.
Cows were randomly distributed into five similar groups for days after calving (tour
animals each). The exprementa' period lasted for 140 days after calving (20 weeks) .
the experimental rations were formulated as follows :G 1 Control: 70 %
concentrate feed mixture (CFM) + 30 % rice straw (RS), G 2: ration 1 : 70 % (CFM) +
30 % ammoniated rice straw (ARS) +bentonite (8) , G 3 : ration 2: 65 % (CFM) +5%
ground corn grain (GCG) + 30 % (ARS) +(8), G 4 : ration 3 : 60 % (CFM) +10%
(GCG) + 30 % (ARS) +(8) and G 5: ration 4: 55 % (CFM) +15% (GCG) + 30 % (ARS)
+ (8) . These proportions were chosen to achieve approxmitley iso nitrogenous ration
containing about 12-13% CPo
The obtained results showed that urea-N concentration for blood serum
ranged from 17.5 (ration 3) to 31.8 (control) mg/100 ml and its levels was
significantly (p < O. 05) decreased by increasing replacement corn grain in the ration
3 & 4 . The serum glucose cocentration ranged between 44.6 to 59.2 mg/100 ml with
different rations and its :evel was significantly (p < 0.05) decreased by increasing
replacement corn grain, compared with the control and ration 1. The average daily fat
corrected milk (FCM) yield was the highest (p < 0.05) with group fed ration 4 (24.2
kg/d), when compared with the other rations. The persistency period with replacement
corn grain and bentonite supplementation was longer than both the control or ration
1. The solids non fat (SNF%), protein yield (kg/d) and lactose yield (kg/d) were
increased (p < 0.05) wit'i increased the replacement of corn grain and bentonite
supplementation, based on the average values, the highest (p < O 05) was with the
ration 4 compared with the other rations. The net energy of ration (NEo Mcal/kg)
values were significantly (p < 0.05) higher with ration 4 (1.8 Mcal/kg) than with the
other rations, but the net energy (NEL Mcal/kg milk) value was not significantly
different among treatments and the highest value was recorded when feeding on
ration 1 (0.615 Mcal/kg milk) but the lowest value was with ration 4 (0.574 Mcal/kg).
The feed conversion (NEL/NEo) values were significantly (p < 0.05) increased with
the control or ration 1, compared with the other ones and the lowest value was
noticed with the ration 4 (31.88%) .The highest value of feed cost was estimated
with ration 4, but the lowest value was with the control. The highest value of the total
output as the price of fat corrected milk (FCM) was recorded with feeding ration 4, but
the lowest value was with the control. The results of return (profit L.E) , showed that
the highest return was obtained when feeding on ration 4, followed by ration 1 and the
lowest was with ration 3.