The Association Between Lunar Phases and Calving Frequency in Montbéliarde Dairy Cows in the Franche-Comté Region, France

The Moon is at the centre of many popular beliefs, including the notion that the number of parturitions increases during Full Moon days, a belief widely held among breeders to anticipate calving periods. However, this association has been rarely explored in dairy cattle farming. This retrospective study was conducted to evaluate the association between the lunar cycles and calving distribution, with particular focus on a potential increase during full-moon nights. Data from 383,926 calvings of Montbéliard breed, recorded between March 2022 and January 2025, mostly in Franche-Comté (98.2%), France, were analyzed using a Generalized Linear Model (GLM). Results revealed a significant association between the lunar cycle and calving distribution. Model-adjusted means were significantly higher than the overall mean during the New Moon and the Last Quarter phases (+2.6%, p < 0.05), and significantly lower during the Full Moon phase (−3.1%, p < 0.01). At the synodic day level, days 21 and 29 presented the highest model-adjusted means (+23.2% and +23.4% above the overall mean, respectively; p < 0.001), while days 4 and 15 presented the lowest (−35.2% and −31.1%, respectively; p < 0.001). Across all seasons, a consistent trend toward increased calving frequency was observed during the New Moon phase, reaching statistical significance only in Spring (+5.7%, p < 0.05). These findings may offer potential implications for veterinarians and breeders, particularly when considering approaches to ensure adequate colostrum intake, which may contribute to improving management of parturition periods.