Fertility measures in Polish Black-and-White cattle. 3. Phenotypic and genetic correlations between fertility measures and milk production traits.

摘要

The objective of this research was to estimate phenotypic and genetic correlations between fertility and milk production traits. The following traits characterizing cow reproduction were studied: non-return rates till 56 and 72 days, age at first insemination, age at conception, calving interval, days open, days to first service, and service period. Data included reproductive traits of 42 283 first-parity Black-and-White cows. Days open and calving interval were calculated for 25 013 cows. The highest phenotypic correlation obtained between protein yield and days open amounted to 0.22; non-return rates showed the lowest phenotypic correlations with yield traits. All genetic correlations between reproductive traits and yield traits were unfavourable. The largest were found between yield traits and days open and calving interval (0.35-0.48), and the smallest for age at first insemination and non-return rate until day 72 (less than 0.1). Fat and protein content showed very small correlations with fertility traits; genetic correlations were also low except for non-return rates, which ranged from -0.55 (between fat content and non-return rate until day 56) to -0.24 (between protein content and non-return rate until day 72). The antagonistic genetic correlations between milk production and fertility traits show that selection for fertility is needed..