Ever notice more birthings around the full moon? Japanese researchers found evidence that the lunar cycle affects calving in Holsteins. Based on 428 spontaneous, full-term deliveries within a three-year period, the scientists found that calvings were less common at new moons than at full moons. Calving rates “increased uniformly from the new moon to the full moon phase and decreased until the waning crescent phase.” The trend was found among cows that had calved in previous years, but not in cows going into labour for the first time.
All the cows were bred with AI and the timing of AI (or ovulation) was not influenced by the moon’s phase. Further analysis showed that cows with predicted calving dates around the full moon to last quarter tended to give birth when predicted, but cows with predicted delivery dates during the new moon to first quarter moon often delayed delivery.
The reason behind the lunar effect isn’t clear. The scientist ruled out the effect of lunar gravity on oxytocin levels, the effect of lunar cycles on the timing of ovulation and the effect of weather. One possible explanation is reduced melatonin secretion around the time of the full moon. The cows were in barns with windows and without artificial lighting at night — the moonlight streaming through the windows may have led to lower melatonin levels, which may have induced labour. The scientists suggest the reason behind the trend in cows may also affect other mammals, including humans (if women were not exposed to artificial lighting).
Source: Lunar Cycle Influences Spontaneous Delivery in Cows. Tomohiro Yonezawa, Mona Uchida, Michiko Tomioka and Naoaki Matsuki. PLoS ONE. Volume 11. Issue 8. August 31, 2016.
- Janet Wallace