Customising lactation length: impact of calving interval, parity, and lactation persistency on milk production of dairy cows

The transition period around calving is a critical phase for a dairy cow. Large changes in both physiology and management increase the risk for disease. In most modern dairy systems a cow faces this transition period every year, as a one-year calving interval (CI) is usually aimed for. Increasing CI reduces the relative amount of transition periods for a cow, thereby potentially reducing the risk for disease and improving fertility. Drawback of an increased CI is a possible reduction in milk yield although estimated effects of an increased CI on milk yield differ among studies. Some farmers in the Netherlands deliberately increase CI by increasing the voluntary waiting period for insemination (VWP), using various strategies to select cows that may benefit from an increased CI. This study aims to gain insight in cow characteristics that can be used to optimize CI for individual cows by assessing how CI, parity, and persistency impact milk production.