RESUMEN
Reproduction and milk production traits of Friesian cows were collected and analysed to examine the relative importance of sire of cow, sire of fetus, season of calving and parity, on performance traits. Sire of cow and sire of fetus affected age at calving, number of services per conception, days open, calving interval, milk yield, persistency and peak yield significantly, but had no significant effect on days from calving to first service. Calving interval was not affected by sire of fetus. Within sire of cow, correlations of number of services per conception with days open and calving interval were high and positive [0.88 and 0.89], and those for milk yield with persistency and peak yield ranged between 0.73 and 0.76. Considering sire of fetus, correlation of calving interval with number of services per conception and days open were 0.79 and 0.89, and that between milk YIELD and persistency was 0.81. They were negative and significant for age at calving with milk yield and persistency [0.55 and 0.60]. For the days from calving to first service with days open and milk yield, they were 0.44 and 0.55. Season of calving had no significant effect on reproduction traits. Parity effects were significant for age at calving, days from calving to first service, milk yield and peak yield, but had no significant effect on calving interval, days open, number of services per conception and persistency