Twenty lactating Friesian cows with average live body weight of 550 ±18 kg in their the 2nd to 5th parity were used to study the effect of replacing yellow corn grains )YCG) by discarded dates (DD) in concentrate feed mixture (CFM) at levels of 0, 33, 66, and 100% (w/w), on their productive and reproductive performance. Cows were assigned randomly to four similar groups (5 in each) according to milk yield, parity and live body weight (LBW). The levels of replacement of YCG by DD in CFM were0, 33, 66, and 100% (w/w) for G1 (control), G2, G3 and G4 as tested rations, respectively.
Results showed that the contents of OM, CP and NFE were higher in YCG- compared to DD-ration, however the content of CF and ash showed an opposite trend. Cows in G3 (66% DD) recorded the highest (P<0.05) digestibility coefficients of all nutrients, nutritive values and the intake of DM, TDN and DCP, followed by G2 and G4, while G1 (control) almost had the lowest values. The pH value in rumen liquor markedly decreased after feeding and its values 3 h after feeding were lower (P<0.05) with the DD-rations than control. The highest TVFA's concentration in rumen liquor was recorded with in G3 after feeding, while the lowest concentration was found in G1 after feeding. Ammonia-nitrogen concentration in G3 was higher before and after feeding than the other treatments. Cows in G3 had the highest concentrations of total proteins, globulin and glucose and the lowest concentrations of albumin and total lipids in blood plasma. Yield as actual milk and 4% FCM were higher (P<0.05) for DD-rations than those of control, being the highest in G3. Cows in G3 recorded the highest (P<0.05) percentages of fat, protein, and total solids in milk. Cows in G3 showed the best feed efficiency (DM, TDN and DCP: 4% FCM) compared with those fed the other rations (P<0.05). Average daily feed cost was higher (P<0.05)in G2 and G3 as compared to G1 and G4. While, cows in G3 showed the lowest feed cost/ kg 4% FCM and the best economic efficiency followed by G4 and G2, while G1 had the opposite trends. Cows in G3 had the best of most reproductive traits as first estrus, first service, service period, number of service /conception and conception rate. It could be concluded that partial replacement of yellow corn grains by discarded dates at the level of 66% as a source of energy in concentrate feed mixture improved the feed intake, digestibility, rumen fermentation activity, yield and composition of milk, economic feed efficiency as well as the post-partum reproductive traits in Friesian cows.