HERD FERTILITY PARAMETERS IN RELATION TO MILK-PRODUCTION IN DAIRY-CATTLE

Relationships among herd fertility parameters and relationships betwee n herd fertility parameters and herd production were estimated for the milk recorded Dutch cattle population. A random sample of 357 herds f rom the milk recording database was used for this study. This dataset contained 30425 records of calvings with a subsequent calving date. Si x fertility parameters were calculated. Production was characterised b y age and season corrected 305 day yield. The strongest influence of m anagement was on timing of first insemination. Results showed that her d fertility parameters should be corrected for environmental effects a lthough small percentages of variation were explained. Herds in which first inseminations were carried out relatively early in lactation on average used more inseminations to breed each cow. At herd level the c orrelation of CI and NINS was almost zero, indicating that different a pproaches can lead to the same average CI. Relatively higher producing cows were first inseminated later than their lower producing herdmate s. High producing herds use more inseminations per conception, but res ults show that a high herd production level can be combined with relat ively good herd fertility parameters.