The same previous milk records used in studying the environmental factors affecting milk production (total of 1797 records of 765 cows) were used to study the genetic factors, repeatability , heritability and sire transmitting ability . The results showed that : The phenotypic and genetic correlations between different examined traits were estimated. Repeatability and heritability estimates of total milk yield, 305 days milk yield, lactation period and 90,180, and 270 days cumulative milk yield were (0.51 and 0.05), (0.45 and 0.02), (0.28 and 0.05), (0.47 and 0.04) and (0.50 + 0.02), respectively. Rank correction between cumulative 270 days / milk yield with each of cumulative 180 and 90 day yield were 0.99 and 0.98 , respectively , and between total milk yield with each of 305 day milk yield and lactation period were 0.97 and 0.96 respectively . Sire had highly significant effect on total milk yield , lactation period and cumulative 180 days milk yield and only significant effect on 305 days yield . Cumulative 90 and 270 days yield . While .Sire had non-significant on all methods for persistency of lactation . Estimating of  sire transmitting ability ( BLUP ) to milk that indieatal the actual values of sire transmitting ability for total milk yield ranged between   (-530 to 744 kg ) , 305 days milk yield ( -444 to 602 kg 0 lactation period ( -39 to 56 days ) and cumulative 90 , 180 and 270 days milk yield were –338 to 189 , -570 to 387 and –633 to 538 kg , respectively . additionally, the percentage of sire having positive  ( BLUP ) ranged from 51.5 to 54.5% for the studied different traits . This means that not all the sires could be consider as a way for genetic improving of the examined traits . Thus the importance of expecting selection the best sire for improving the examined milk yield traits have great value .