Fertility measures in Polish Black-and-White cattle. 2. Genetic parameters of interval measures

Genetic parameters of service period, calving interval, days open, days to first service and days of pregnancy were estimated. Data were records of 42,283 cows. Heritabilities of all traits in first parity were low and ranged from 0.044 for calving interval to 0.092 for service period. Heritabilities of all intervals decreased in consecutive parities, and in the third parity were close to zero for days open and days to first service. The highest genetic correlation was found between calving interval and days open (0.99), days to first service and days open (0.74), and days to first service and calving interval (0.72). Service period was highly correlated genetically with age at first service (0.72), age at conception (0.90) and age at calving (0.90). The genetic correlation between days open and age at first insemination was 0.44. Genetic correlations of fertility traits between parities were highest when estimated for first and second parity, and ranged from 0.92 to 0.99.