Flat lactation curves are believed to be associated with fewer health and reproduction problems. Here you can read more about this trend among dairy farmers from a scientific point of view.
Since 2006, the Nordic Cattle Genetic Evaluation (NAV) has calculated breeding values for persistency, which provides information about the shape of the lactation curve.
For example, bulls with EBV (Estimated Breeding Values) above 100 (high persistency) will produce daughters that have a flatter lactation curve with lower yield than expected in the first part of the lactation, and a higher yield than expected in the last part of the lactation, compared to bulls with a lower EBV for persistency.
Recently, dairy farmers have shown an increased interest in lactation persistency as a management tool because flat lactation curves are believed to be associated with fewer health and reproduction problems.
But how is persistency calculated?