PRODUCTIVE AND REPRODUCTIVE PERFORMANCE OF LACTATING FREISIAN COWS FED RATIONS CONTAINING DIFFERENT LEVELS OF CORN SILAGE

This study aimed to evaluate incorporation of different levels (25, 50 and
75%) of corn silage (CS) as a replacement of concentrate feed mixture (CFM) on
chemical composition of tested ration, digestibility coefficients, milk production and
milk feed efficiency of lactating Friesian cows. Eighteen animals average 530.6±37.3
kg LBW within 1-5 lactations were randomly divided into three similar groups the t"
group (G1) was fed CFM, CS and berseem hay (BH) at 66: 25: 9 ratio (DM basis),
respectively. The 2nd group (G2) was fed CFM, CS and BH at 41 : 50: 9 ratio,
respectively. While the 3'd one (G3) was fed CFM and CS at 25 : 75 ratio.
Chemical analysis and nutritive values as TDN and DCP (66.12 and 6.84%,
on OM basis, respectively) of CS indicated that CS could be considered as a good
feeding source for ruminant animals. The present results indicated that contents of
CP, EE, NFE were the highest (14.2, 3.25 and 58.7%, respectively) in ration (R1) of
the control group (G1) as compared to other rations, while R3 of the 3'd group (G3)
had the highest CF content (21.5%). Average daily total DM and TDN intakes did not
differ significantly among groups. However, DCP intake was significantly (P<0.05)
lower only in G3 than G1 (1.19 vs. 1.61 kg/h/d). Digestibility coefficients of OM, OM,
CP, EE and NFE did not differ significantly (P<0.05) higher in R2 (66.97%) and R3
(68.18%) than the control rations (58.5%). R2 and R3 showed significantly (P<0.05)
higher TDN values (67.54 and 67.62%) than that of R1 (66.61%), while R2 and R3
had significantly lower OCP values (8.97 and 7.82%) than the control rations
(10.06%), being significantly (P<0.05) higher in R2 than R3.
Average actual milk yield, 4% FCM and adjusted milk yield were significantly
(P<0.05) higher in cows fed R2 and R3 than those in cows fed the control ration
(18.59 and 18.98 ; 18.33 and 18.98 and 4073.7 and 3917.1 vs. 16.49, 15.95 and
3574.8 kg respectively).
Feed conversion and feed efficiency were significantly (P<O.05) higher in
cows fed R2 and R3 than R1 in terms of total DM, TDN and DCP intake per kg 4%
FCM. The differences between cows fed R2 and R3 in feed conversion and milk feed
efficiency were not significant for DM and TON intake, while significant (P<0.05)
differences were found between R2 and R3 in term of DCP intakelkg milk produced,
being higher of cows fed R2 than R3. Economic feed efficiency was markedly higher
in cows fed R2 (266.7%) and R3 (328.94%) than the control (205.35%), being higher
for R3 than R2 (Table 7). Cows in G2 significantly (P<0.05) showed the best
reproductive performance in terms of the shortest service period (39.6 d) and days
open (88.2 d) and the lowest number of services/ conception (2.3 sIc) Table 8.