Does the Phase of the Moon Affect the Sex of Your Foal… or is it an Old Wives Tale?
Photo Credit: Brittany Bevis
Equine Science Update by: Mark Andrews
Eleven months is a long time to wait to see if your foal is a colt or a filly. The foal’s gender may have a significant effect on its value to the breeder. For example, among Polo Horse breeders there is a higher demand for female offspring than for males.
An ultrasound scan can be used to find out in advance whether the foal is a colt or a filly. Advanced techniques such as gender selection of sperm can be used to influence the sex of the foal.
But what about other less high-tech solutions? The phases of the moon may influence various biological processes. Is there any truth in the suggestion that the phase of the moon at the time of conception can influence the sex of the foal – or is it just an old wives tale?
José Javier Aguilar and colleagues from the Universidad Nacional de Río Cuarto, in Córdoba, Argentina, have recently published research in the journal Chronobiology International. Their study aimed to determine whether there was a significant association between the phase of the moon at the time of mating and the sex of the foal that was subsequently born.
The researchers retrieved information from the Argentinian Stud Book on all matings registered for Thoroughbred and Arab horses between 2003 and 2011. They then examined the data to see if there was any association between the gender of the foal and the phase of the moon at time of conception.
They analyzed a total of 65,535 pregnancies, which produced 50.96% fillies and 49.04% colts. They found no correlation between lunar phase at conception and ratio of male to female foals subsequently born.
They conclude that “managing the breeding dates in relation to lunar cycles in order to manipulate the sex ratio of the offspring is not a viable option in horses.”
For more details see:
Lunar cycles at mating do not influence sex ratio at birth in horses.
Aguilar JJ, Cuervo-Arango J, Santa Juliana L.
Chronobiol Int. 2014 Aug 25:1-5.
doi: 10.3109/07420528.2014.950738
