This study was performed on productive data collected from private farm of Holstein Friesian cows.
The objective of this study was to evaluate the effect of days in milk (DIM), peak milk yield (PMY),
dry period (DP), calving interval (CI), parity, and season of calving on 305-day milk yield (305-
DMY). And the effect of 305- day milk yield (305-DMY), peak milk yield (PMY), days in milk
(DIM), parity, and season of calving on lactation persistency. We found that DIM, parity, and PMY
had significant effect on 305-DMY, the highest milk production was obtained when DIM more than
357 days and in the 1st lactation. Moreover, PMY, 305-DMY, and season of calving had significant
effect on lactation persistency. In addition, average estimated breeding value (EBV) for 305-DMY,
PMY and CI was higher in sire than in cow and dam. Also, Average estimated breeding values for
lactation persistency, DP, and DIM were higher in dam than in cow and sire