The present study aimed to display effects of age at first services, age at first calving (AFC), calving interval, days open, number of services per conception, days dry, season of calving on total milk yield (TMY) and 305 milk yield (305MY). Also, to estimate effect of season and parity on calving interval (CI) and days open and then the effect of level of production on service per conception, age at first service, age at first calving, calving interval and days open. Heritability estimates for 305-day milk yield (0.18), days open (0.18), dry period (DP) (0.12), TMY (0.17) and CI (0.19). High heritability estimates were obtained for AFC (0.68) and lactation length (LL) (0.78). There were high positive genetic and phenotypic correlations between total milk yield and 305-day milk yield and low genetic and phenotypic correlations between most studied traits. Average EBV for AFS, AFC and 305MY were higher in cow than sire and dam. Also, average EBV for LL and DO were higher in sire than in cow and dam and average EBV for CI and DP were higher in dam than in cow and sire. But TMY was equal in sire and dam and higher than cow.

This study was performed on 1480 productive records collected from private farm of Holstein Friesian cows. In addition, collections of 70 milk samples for the measurement of somatic cell count (SCC). This study aims to evaluate the effect of some non-genetic factors (days in milk (DIM), peak milk yield (PMY), dry period (DP), calving interval (CI), parity, and season of calving) on total milk yield (TMY), and studying the effect of305-day milk yield (305-DMY), peak milk yield (PMY), days in milk (DIM), parity and season of calving on mastitis in Holstein Friesian cows. All data were analyzed by general linear model (GLM) using SAS software ver.9.1.3. The current results revealed that DIM and parity had a significant effect on TMY, where the highest milk yield was obtained when DIM were more than 357 days and in the 3rd lactation season. Season of calving showed a significant effect on occurrence of mastitis, where the highest incidence of mastitis was recorded for spring calvers.

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.