This study was conducted to investigate the effect of supplementation of zinc sulfate and / or   manganese sulfate on the digestibility and  ruminal activity, some blood parameters   and   productive performance of Friesian calves .   Twenty calves with initial body weightof 262±.7kg in a 180 days experiment were chosen and divided into four similar groups (5 calves each). The control group was fed on concentrate feed mixture (CFM) + berseem hay (BH) + rice straw (RS), while 1^st tested group was fed on the  control ration + 40 mg zinc sulfate(ZnSO₄) / kg DMI, the  2^nd tested group was fed on the control ration + 40 mg manganese sulfate (MnSO₄)  / kg DMI of and the 3^rd tested group was fed on the control ration + (40 mg ZnSO₄+40 mg MnSO₄)/kg DMI  .  Adding either zinc sulfate or manganese sulfate or mixture of both elements   increased (P<0.05) the nutrients digestibility and in turn the nutritive values (TDN and DCP). Adding  zinc sulfate or manganese sulfate  reduced ammonia-N  and  increased TVFA's . With respect to blood parameter, rations supplemented with Zinc or Mn sulfate appeared to higher total protein, albumine and lower globuline and urea concentration. Daily gain of the animals fed supplemented rations (tested groups) were higher than that of the control group being 0.969, 0.883 and 1.037 kg for animals fed rations supplemented with Zn , Mn and both of Zn plus Mn sulfate, respectively. Consequently, feed efficiency was better for tested groups which was give more gain with less feed intake and lower feed cost.    It could be concluded that addition of 40 mg zinc sulfate and / or manganese sulfate/kg DMI improved nutrients digestibility, economic efficiency and daily gain of Friesian calves.