The effect of substitution of concentrate feed mixture (CFM) by yellow corn grains
fed along with rice straw ration of lactating cows on their performance for miik vie-ac
and composition as weli as blood metaooiites was investigated. Five lactating Friesian
cows were used in a " Swing—over" design. with mean metabolic body size (BW" '3 i
of 102 kg were used in this study. All animals were in the 2nd to 41'"h lactation season.
The experimental rations were formulated as foiiows 3R1: ration 1: 69 % concentrate
feed mixture (CFM) + 31 We rice straw (RS) (as a control ration), R2: ratio-n 2: 62 We
(CFM) + T% "/e ground corn grains (GOG) + 31 % {RS), R3 ration 3: 55 % (CFM)
+15% (GCG) + 31' % (RS). These proportions were chosen to achieve approximately
iso nitrogenous, iso—caloric rations containing about 122-13991: crude protein {CP}
and 2.14 to 2.24 Mcal f kg as recommended by (@rskove et a! 19T2) to ensure
maximal rate to fermentation in the rumen..
The results showed that the intake of rations by cows was fixed and calculated
as the percentage of roughage to concentrate ratio to satisfy their recommended
reguirrnents. The total DM intake gfkg 8W0 "‘3 fday of R1, R2 and R3 were 209, 209
and 216.5 respectively. The crude protein intake (CPI gf kg awa "'3 id) for R1, R2 an
R3 were 2T.3, 26.3 and 26.? respectiveiy. The urea-N concentration ranged from
18.03 to 25.?5 mgi100 ml in the blood-serum, and its ievels was significantly (p < 0.05)
increased when feeding on R1 or R3 than R2. The average daiiy fat corrected miik
(FCM 3.5%) yield was the highest {p < 0.05) with R3 (22.2 kgfhid) than feeding on R1
or R2 (1?.89 and 17.22 kgihid, respectively),but without significant effect, while the
net energy {NEL Mcaifkg milk) vaiue was higher significantly (cs-0.05) when feeding on
R1 or R3 (0.639 and 0.656 Mcaiikg milk respectively) than feeding on R2 (0.539
iv-icaiikg milk) On the other hand- fat yield increased {p < 0.05) when feeding on R3
(0.??8 kgic‘j than feeding on R1 or R2 (0.586 and 0.494 kgid respectively). Regarding
the milk composition, the total solids (TS), fat, totai N, protein and non casein nitrogen
(NCN)% were significantly (ps005) increased when feeding onR1 or R3 than feeding
on R2. The whey protein nitrogen (WPN) or whey protein (WP) concentrations were
increased (ps005) when feeding on R1or R3 than feeding on R2, while casein "Xe
decreased (ps005) when feeding on R3 than feeding on R1 or R2. The highest value
of production efficiency was that recorded with R3 while the lowest value was with R1.
The highest return was also obtained when feeding on R3, while feeding on R1 or R2
showed negativeiy effect on the return.