INFLUENCE OF STALLION AGE AND SEASONALITY ON FOAL SEX DETERMINATION IN THE QUARTER HORSE BREED: A RETROSPECTIVE ANALYSIS AND INTERNATIONAL COMPARATIVE REVIEW
DOI:
https://doi.org/10.56238/revgeov17n1-141Keywords:
Equine Reproduction, Fetal Sexing, Seasonality, Lunar Cycle, Quarter HorseAbstract
Sex determination in mammals is genetically defined at the moment of fertilization; however, environmental and natural factors have historically been empirically associated with modulation of the sex ratio at birth. In modern equine production, particularly in the Quarter Horse breed, the influence of reproductive seasonality, stallion age, and natural cycles, including lunar phases, remains a recurring topic among breeders and researchers, despite limited scientific support. This study aimed to evaluate the influence of reproductive seasonality and stallion age on foal sex determination in the Quarter Horse breed, as well as to critically analyze the lunar hypothesis based on national and international scientific literature. A retrospective analysis of reproductive records from 750 foals sired by five stallions was conducted, considering stallion age at conception, time of year, and foal sex. Statistical analyses included descriptive statistics, correlation tests, and Scheffé’s test at a 5% significance level. The results indicated variations associated with reproductive seasonality and stallion age; however, no consistent causal effect on foal sex determination was observed. No significant association was found between lunar phases and sex ratio at birth in equines. Comparative analysis with studies conducted in equines, cattle, dogs, and humans reinforces the distinction between temporal correlation and biological causality, indicating that the lunar hypothesis lacks physiological and statistical support in equine reproduction.
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