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. |
