Does the Moon Phase Affect Horses’ Colic Risk?

While many causes of colic are well-researched and well-known, some cases are still hard to explain. Could they be linked to subtle factors, such as weather changes or moon phases?

Lucile Vigouroux, a student at Centenary University, in Hackettstown, New Jersey, and co-authors Danielle Ferriola; Jesslyn Bryk-Lucy, DVM; and Linda Ritchie, MBE, recently conducted a study to investigate. Vigouroux presented their findings at the 2019 Equine Science Society Symposium, held June 3-6 in Asheville, North Carolina.

First, the team surveyed nearly 200 horse owners, trainers, and veterinarians to determine their perceived top three colic causes, which were:

  • Dehydration (49%)
  • Weather (46%)
  • Nutrition (42%)

They also asked them during which moon phase they thought horses colicked most frequently, and 63% chose the full moon. (“None” was not an option.)

Then, Vigouroux and her colleagues tracked colic incidence among 100 of the university riding program’s horses, along with atmospheric temperature, barometric pressure, relative humidity, temperature, and moon phase in the preceding 12 and 24 hours of each case.

While they found no significant association between colic and any of the weather metrics, Vigouroux did note a weak but significant association between colic and moon phase. Colic incidence was highest (60%) during waxing gibbous (the 3.5 days before a full moon) and full moon phases. Three out of the five days that multiple horses colicked, for instance, occurred during these two phases.

Studies have shown there to be a lunar influence on humans and animals, from fertility levels to hormone fluctuations to immune response. More research into its effect on equine colic, however, needs to be done to make a strong association. Bryk-Lucy is currently performing a three- to five-year study specifically on moon phases and colic.

In the meantime and on a practical level, said Vigouroux, caretakers might want to monitor horses and take extra colic prevention steps during waxing gibbous and full moon phases.